Informed Consent and Implications for Infection Control

The principle of informed consent, as it applies to veterinarians caring for animals, implies that owners have the right to be provided with adequate information before treatment so that they can make appropriate decisions for their animals and themselves.^13,14 As professionals with specialized training, veterinarians are expected to have knowledge about the health and care of animals that goes beyond that of someone without this training. One of the components that experts generally agree is part of the informed consent process is the disclosure of potential risks that may be associated with a veterinarian’s management of a client’s animals, particularly in situations in which there is greater than average risk for a particular adverse consequence.¹⁵ It is reasonable and prudent for veterinarians to routinely disclose the potential for nosocomial infections as part of the informed consent process for all patients. This is especially true for patients with an enhanced risk of acquiring a nosocomial infection (e.g., because of required invasive procedures or because patients are immunocompromised). However, it is also true that if veterinarians know there is an increased risk of nosocomial infections at a facility, there is likely an ethical and legal obligation to disclose before admission how this risk pertains to new patients. In situations in which there is an increased risk of nosocomial infection (if not in all veterinary care situations), it is extremely prudent to document in writing the informed consent process with clients.

Paying for Infection Control Activities

As mentioned previously, procedures used to decrease the risk of nosocomial infections inherently increase labor and material costs related to patient care. If infection control activities are an essential part of delivering veterinary care, then it should reasonably be expected that these costs will be passed on to clients, and it should not be expected that they will be paid for by veterinarians or hospitals. This includes the costs for additional care that is necessary to treat complications associated with nosocomial infections. This assumes that prudent and reasonable precautions have been employed in an effort to manage nosocomial disease risks for patients. In addition, if nosocomial infections are an expected risk related to care of any patient, then veterinarians and hospitals should develop plans for management of financial issues related to these risks. It is also important to differentiate consideration for how charges might be presented to the client from how costs for infection control activities are accounted for. These costs might be passed on to clients by directly accounting for each item, which is most reasonable when there are specific charges that can be attributed to a specific patient (e.g., increased costs related to care of a specific patient in isolation). However, this is less applicable to costs related to care and protection of more than one patient (e.g., costs related to cleaning and disinfection of the environment). In these cases it may make more sense to compensate for costs by aggregating expenses into a general fee category related to infection control (such as a daily biosecurity surcharge) or to include these costs in overhead costs that are covered by general admission or hospitalization fees. In special circumstances, such as when it is necessary to investigate or mitigate against suspected outbreaks of infections, it is useful to have a contingency fund that has been accrued and earmarked to pay for unforeseen expenses such as mass testing, additional labor related to cleaning and disinfection, and so on. Administrators should ensure that the possible need for these monies in case of infection control emergencies is considered and that fee schedules are sufficient to allow development of this type of reserve fund.

Cleaning

Cleaning is defined as the removal of all visible debris.¹⁷ It is arguably the most important step in decontamination of animal environments. Even the best disinfectants will be minimally effective when used in the presence of moderate volumes of dirt and organic debris such as feces and bedding material. Dirt and debris hamper disinfection by inactivating many chemicals, acting as a physical barrier between disinfectants and microorganisms, and providing a nutritional source for microorganisms. Not only does cleaning enhance efficacy of the disinfection process by providing optimal conditions for desired biochemical reactions, cleaning can actually remove a majority of microorganisms so that fewer need to be killed by disinfectants. Therefore removal of as much organic debris as possible is required for optimal disinfection. This involves manual labor consisting of removing all bedding and feces and scrubbing all surfaces to remove adherent debris and biofilms. Detergents should be used to loosen organic debris, emulsify fats, and decrease biofilm formation. The disinfectant to be used must be considered when choosing a detergent because there can be interaction between chemicals in detergents and disinfectants.

Because of the effort required to clean and scrub a stall, less labor-intensive methods are often sought. For example, cleaning with high-pressure (>120 psi) power washers is frequently employed in barns and hospitals. There are theoretic advantages that seemingly justify use of high-pressure washers, especially when they are designed to dispense high-temperature water and steam. However, whereas power washing is quite helpful in removing organic debris, infectious agents can easily be aerosolized and dispersed over wide areas if pressure washers are used indiscriminately. The true risk related to the use of high-pressure washers is unclear. However, the convenience of using high-pressure systems must obviously be balanced with more intensive manual cleaning methods in order to minimize untoward consequences. Using high-pressure systems on surfaces with large amounts of gross contamination should clearly be avoided.¹⁸ In areas likely to be contaminated with important contagious pathogens (e.g., isolation facilities), it is logical to minimize use or at least use them only as a secondary cleaning process on surfaces that have been previously manually cleaned and disinfected.

Disinfection

Even with proper cleaning and selection of an appropriate disinfectant, disinfection errors can occur. It is critical that disinfectants be used at appropriate concentrations allowing for adequate contact time. It is also important to consider that microbial responses to disinfectant exposures are not uniform. There is tremendous variation in the ability of microorganisms to tolerate cleaning and disinfection. Most enveloped viruses are easy to eliminate, whereas protozoal oocysts, nonenveloped viruses, and bacterial spores may be difficult or impossible to kill.¹⁹

For disinfection to be effective, a few key factors must be considered: the presence of organic debris, disinfectant concentration, temperature, and contact time. Organic debris inactivates disinfectants to varying degrees, emphasizing the need for careful cleaning. Most disinfectants are available as concentrates and must be diluted before use. Excessively dilute disinfectant solutions may have little or no effect, whereas excessively concentrated solutions can be dangerous to use in addition to being wasteful of resources. Dilution of disinfectants is an important process and must be performed by measurement, not estimation. One solution that makes it easier to ensure that disinfectants are appropriately diluted is to use metered dispensing units that can be either wall mounted or attached to the end of a hose. For some disinfectants, different concentrations may be recommended for different situations. Test strips that can commonly be purchased from restaurant supply companies can also be used to verify appropriate dilution and activity disinfectant solutions. This is especially important when stock solutions are prepared for use over time. Cleaning staff must be informed of the importance of disinfectant dilution and trained in proper methods. Contact time is critical, particularly for certain disinfectants and difficult-to-kill microorganisms. If disinfectants are applied and immediately rinsed away, there is little chance that they can be effective. Most disinfectants require 10 to 30 minutes of contact time. Chemical reactions that produce disinfection are slowed in cold temperatures, which should be considered when determining the amount of contact time that is required. Disinfectants should never be combined because of the potential for inactivation and production of toxic gases.

Disinfection processes can be divided into three categories: high-level, intermediate, and low-level. High-level disinfection involves elimination of all viruses and vegetative bacteria but not all bacterial and fungal spores or protozoal oocysts. High-level disinfection is, in reality, difficult to attain and is uncommonly used. Intermediate disinfection involves eliminating all vegetative bacteria but not necessarily all viruses (especially nonenveloped viruses), spores, or oocysts. Low-level disinfection results in elimination of most but not all potentially pathogenic bacteria. Items requiring disinfection should be classified as to the level of disinfection required, examples of which are shown in Box 46-1.

Disinfectants

It is critical to be aware that all disinfectants do not have the same effectiveness. As with antimicrobial drugs, disinfectants have a spectrum of activity that can be highly variable among disinfectant classes (Table 46-1) Choosing the most appropriate disinfectant can be complex, involving a variety of factors including spectrum of activity, relative efficacy in the presence of organic debris, toxicity to animals and humans, potential damaging effects on certain surfaces, cost, and potential environmental effects. There is no standard disinfectant to be used in all situations in large animal facilities, although oxidizing agents such as accelerated stabilized hydrogen peroxide and peroxymonosulfate are increasing in popularity because of their broad spectrum of activity, acceptable performance in moderate amounts of organic material, relatively rapid action at room temperature, relative safety for personnel, and environmental friendliness. Other options may be appropriate in certain situations. When disinfectants with a narrower spectrum of activity are used as the primary disinfectant, protocols should be in place to use alternate products should certain situations be encountered that require a higher level of activity.

Table 46-1 Disinfectants Commonly Used in Veterinary Medicine*

Effect of Surface Material on Cleaning and Disinfection

The material to be cleaned and disinfected can also have a tremendous impact on efficacy. Many surfaces found in large animal clinics and farms are not amenable to thorough cleaning and disinfection. These include unsealed wood surfaces, unsealed block, dirt flooring, and areas that are difficult to clean.

For stalls, solid walls with a sealed surface are optimal for disinfection. This may be difficult to achieve; however, there are certain procedures that can be performed to facilitate disinfection.¹⁸ Cement block walls can be reasonably well sealed with at least two coats of good-quality enamel. Wood walls can be sealed using two or more coats of marine epoxy. Regular maintenance of stalls is required to seal defects that occur from kicks or chewing.

The optimal floor surface, in terms of cleaning and disinfection, is a smooth, solid, completely sealed surface. However, surfaces meeting these criteria are not all amenable to animal housing, so a compromise may be required. Finding the right balance of floor cushion, traction, durability, ease of cleaning, and cost is difficult. Regardless, certain key factors should be considered. The floor should be completely sealed so that water (and pathogens) cannot seep underneath, as this creates an obvious environmental reservoir and prevents adequate contact with disinfectants. Damaged stall matting has been cited as the likely environmental reservoir associated with serious outbreaks of nosocomial disease.¹⁰ If obtaining a seamless, water-impervious floor surface is not possible, floor coverings should be completely removable (e.g., rubber mats over sealed concrete floor) and must be removed regularly for disinfection. Remember that dirt, sand, and other organic materials cannot be disinfected and are therefore unsuitable for permanent flooring in hospital stalls or other veterinary care facilities. If sand is required for care of orthopedic patients, plans should be made to completely remove and discard this material between every patient.

Animal Contact Items

After use, all items in a patient’s stall should be considered potentially contaminated with pathogens that the animal might be shedding. Therefore for patients suspected or known to have contagious diseases, every item in the stall should be treated as a source of infectious material and must be appropriately decontaminated or discarded. Many stall items may be difficult to disinfect, or it may not be possible to be confident in the ability to fully decontaminate them. If it is cost effective, disposal of these items is ideal. Otherwise, standard principles of cleaning and disinfection apply. It must be recognized that rough, damaged, and permeable surfaces may be very difficult to adequately disinfect. Particular attention should be paid to disinfection of surfaces that patients contact orally, such as feeders and water bowls, and surfaces likely to be contacted by hands of personnel. Appropriate decontamination of automatic water bowls can be problematic. Ideally, the water supply should be turned off, the bowl should be drained and cleaned, and disinfectant should be applied for an appropriate time before the bowl is rinsed and the water is turned back on. Nets used to hold hay have a high likelihood of contamination and are difficult to disinfect without use of gas or plasma sterilization techniques. Therefore their use should be avoided if possible.

Certain items may be at particular risk for contamination. For example, thermometers used on animals with salmonellosis are almost assuredly contaminated, and complete disinfection of digital thermometers is very difficult. It is reasonable to dedicate thermometers to individual patients and discard them when they are no longer required. An alternative is the use of disposable temperature strips, which are sometimes used in human medicine. These have not been specifically validated but are routinely used in some large animal hospitals.²⁰

Twitches and muzzles have a high potential for contamination with pathogens such as Streptococcus equi and methicillin-resistant Staphylococcus aureus (MRSA). Rope used for twitches is extremely difficult to disinfect, apart from removing the rope for autoclaving. Chain twitches are easier to disinfect, but many find them less desirable to use. The ideal twitch material is easy to disinfect and atraumatic and provides good grip on the nose. It is debatable whether the ideal material is available at this time. Twitches should be routinely disinfected to the best of degree possible, considering the material. Consideration should be given to regularly changing or autoclaving rope used for twitches and routinely decontaminating twitches with the understanding that complete disinfection may not be possible. Twitches that are used on animals harboring nasal or upper respiratory tract pathogens should be considered contaminated and material discarded or disinfected.

Few areas show a greater difference in approach to infection control between human and veterinary medicine than the handling of needles after use. In human medicine, recapping of needles is strictly forbidden because of the potential for needlestick injuries and subsequent exposure to life-threatening blood-borne pathogens. In veterinary medicine, recapping of needles is very common, and needle-stick injuries are not perceived to be a significant health threat to veterinary personnel. Currently there are minimal risks to veterinary personnel in almost all situations regarding blood-borne transmission of infectious agents from large animals. However, infectious disease hazards clearly are continuing to emerge, and it is prudent to develop safe practices that minimize the potential for exposure to blood-borne pathogens that might be transmitted from domestic large animals.

Hand Washing

Washing with antibacterial soap has been the standard method of decontaminating hands of health care workers for over a century. However, the potential benefits of this practice generally are never realized because of failure to use appropriate methods or failure to wash hands at all.²¹ Common errors in hand washing include inadequate duration of hand washing, failure to use soap, use of contaminated items to dry hands, and contamination of hands immediately after hand washing (e.g., through contact with contaminated faucets or door handles). An appropriate technique for hand washing is outlined in Box 46-3.

The importance of the type of soap used in hand washing is also often overlooked. Plain soaps, those without antibacterial agents, have minimal direct antibacterial activity. The main benefit of these is assistance with removal of dirt and organic debris, although efficacy data are conflicting. The use of plain soap can slightly decrease bacterial numbers on hands, but studies in human medicine have failed to demonstrate effective removal of significant pathogens from the hands of hospital personnel.²² Also, the routine use of plain soap can at times be associated with increases in numbers of bacteria carried on hands if use of these products, results in skin damage and irritation through drying.²³ Plain soaps are therefore not an optimal choice for routine use in medical settings, but use is certainly preferable to not washing hands in the absence of suitable alternatives (such as in field settings).

Most soaps used in hospital settings contain biocides such as triclosan or chlorhexidine. Both of these can produce greater decreases in skin contamination compared with plain soap, and both compounds have antibacterial effects that persist after application,²¹ although the duration of activity is shorter against gram-negative organisms (especially Pseudomonas species).²¹ Iodine and iodophors have been used as skin disinfectants and have a broader antibacterial spectrum. However, both (particularly iodine) can be irritating to skin and are less commonly used for routine hand washing and skin disinfection in medical personnel. In addition, some people become sensitized to skin contact with these products.

Compliance with hand washing protocols is often poor for a variety of reasons. The time required is a major factor, particularly in situations where contact with a large number of patients is likely. Although hand washing requires less than a minute to complete, if it is indicated 100 times in a day, cumulatively this represents a significant amount of time committed to this activity. Lack of convenient access to proper hand-washing facilities is also frequently a problem. If access to sinks with running water, soap, and disposable towels is not convenient (i.e., not adjacent to where animal contacts occur), then it is less likely that hand-washing protocols will be rigorously followed. Regardless of the type of soap used, frequent hand washing can also lead to skin irritation,²¹ which compounds compliance problems by making people reluctant to wash their hands and by making hand surfaces more amenable to colonization by bacteria.

Nail care and jewelry can also be significant impediments to achieving optimal levels of hand hygiene.²⁴ Colonization with higher bacterial numbers, colonization with bacterial pathogens, and outbreaks of infectious disease have been reported in human hospitals in association with effects related to long fingernails and artificial nails.²⁵ Studies have shown that these hamper effective hand disinfection, and many health care facilities, particularly intensive care units, prohibit their staff from having long (≥¼ inch) or artificial nails. The role of these factors in risks to patients in veterinary settings is unclear, but some veterinary facilities have developed similar protocols and restrictions.

Waterless Hand Sanitizers

An alternate approach designed to make hand hygiene easier and more accessible involves the use of waterless hand sanitizers. Most waterless hand sanitizers use varying concentrations of alcohol (isopropanol, ethanol, n-propanol, or a combination), whereas a few products contain alcohol plus biocides, or biocides alone. Alcohol products are most commonly available, with concentrations ranging from 60% to 95%. Most products are available as gels, but newer products are dispensed as foams, which may increase acceptability of products. Products with alcohol concentrations >95% are less effective because the presence of water is important for the bactericidal activity. Alcohols have excellent effect against gram-positive and gram-negative bacteria but not bacterial spores or protozoal oocysts.²¹ Antiviral effects are variable, with less reliable effects against nonenveloped viruses. Alcohol-based products have been shown to have good effect on reduction of hand contamination of health care workers and have been shown to be more effective than standard hand washing.²⁶ Frequent contact with alcohol can lead to significant drying of skin, so most commercial products contain emollients, humectants, or similar skin-conditioning agents. Alcohol-impregnated towelettes are also commercially available but contain a small volume of alcohol and are no more effective for hand decontamination than washing with plain soap.²⁷

One concern that is sometimes expressed about waterless hand sanitizers is their activity in the presence of organic debris. This is a particular concern in large animal practice, where the likelihood of gross contamination is high and access to hand-washing facilities is sometimes limited. However, a study of the efficacy of hand sanitizers on hand disinfection after performing physical examinations in horses reported that both alcohol and alcohol-chlorhexidine hand sanitizers were more effective for decreasing bacterial contamination than washing hands for 15 seconds with antibacterial soap.²⁸ This level of disinfection was noted even though the culture fluid collected off the hands was visibly dirty, indicating that there was a reasonable amount of gross contamination. Thus, waterless hand sanitizers are likely to be effective in normal large animal practice situations. When there is readily apparent contamination of the skin, however, debulking of the hands is probably required for optimal effect. It is important to remember that alcohol-containing products are flammable. Although very rare, fires have been associated with exposure to open flame. Common sense, and ensuring that hands are rubbed together until all the alcohol has evaporated, should greatly minimize any risks.

Although most available products contain alcohol alone, some commercial products contain alcohol plus other biocides such as chlorhexidine. Some of these products have sufficient efficacy such that they are widely used for presurgical hand disinfection. The main advantage of using this combination of products is the residual antibacterial effect that the chlorhexidine confers. Some users complain of a “sticky” feel to the skin, which is one of the reasons that this combination is less commonly used for routine situations.

One of the main advantages of waterless hand sanitizers is their portability. It is difficult to make water sources for hand washing portable or always accessible, but these products can be easily placed in ambulatory vehicles, can be carried by individual staff members, and can easily be placed throughout hospitals. Therefore there is a greater likelihood of obtaining compliance by facilitating access. Unfortunately, regardless of the types of products used, compliance with hand hygiene is often a major problem.^29,30 Infection control programs need to address hand-hygiene compliance through a variety of means to increase use of this critical infection control tool.

Surgical Hand Antisepsis

Scrubbing of the hands and forearms with disinfectant solutions is a standard practice before surgery. Recommended techniques vary somewhat but typically involve a 5-minute scrub with antimicrobial soap. Some studies have reported acceptable hand disinfection with 2- or 3-minute scrubs.³¹ Other studies have demonstrated that a two-step approach using a 1- to 2-minute surgical scrub followed by application of an alcohol-based hand sanitizer is as effective as a 5-minute surgical scrub.³² One concern with repeated surgical scrubbing is the potential for skin irritation and subsequent increases in bacterial contamination. This has led to evaluation of brushless techniques, such as direct application of waterless hand sanitizers. It has been shown that brushless application of a preparation containing 1% chlorhexidine gluconate and 61% ethanol reduced hand bacterial counts more than did brush application of 4% chlorhexidine soap.³³

There may be some concern about sole use of brushless techniques in situations where there may be moderate debris contamination, as could be encountered in veterinary applications. Various hybrid techniques have been recommended, including performing a hand wash or full surgical scrub at the beginning of the day, followed by application of a waterless hand sanitizer product as the sole hand antiseptic technique for subsequent procedures, or performing a brief hand wash before application of a waterless hand sanitizer. The main advantage of these may be elimination of alcohol-resistant bacterial spores.³⁴ One factor to consider, however, is that alcohol products may work better on dry hands, so hands should be allowed to thoroughly dry if hands are washed before application of an alcohol hand sanitizer.³⁴

Use of Barrier Precautions

Basic barrier techniques should be used in all veterinary hospitals. Standardized, clean protective outerwear should be worn over hospital-dedicated attire for any patient contact, regardless of the anticipated nature of contact or the assumed infectious disease status of the patient. The need for other barrier items varies with circumstances and is often dictated by the type of disease syndrome being managed (e.g., diarrhea or gastrointestinal disease, respiratory disease, wound infection, fever of unknown origin) as opposed to as opposed to specifically documented infections or diseases (e.g., patients that are culture-positive for contagious pathogens). Other factors that might indicate a need for additional barriers include farm of origin (e.g., farms with endemic S. equi equi or rotavirus infections) or a patient that is considered to have an increased risk of infection (e.g., compromised neonates). Gloves, gowns, and overboots are the items most commonly used for additional barrier protection, but masks, caps, and eye protection may also be required at times. In some facilities, overboots are not used in all areas, but personnel are required to wear footwear that can be readily disinfected, and disinfection of this footwear is required after exiting potentially contaminated areas.

Limitations of Barrier Precautions

The greatest limiting factors associated with use of barrier precautions in infection control are poor compliance and improper use. Written protocols should be developed that document practical use protocols for barrier precautions. These should specifically state when additional barriers are required; it is not possible to achieve consistent results if protocols are ambiguous or suggest too much discretionary interpretation. In addition, it is critical to educate personnel regarding the need for barrier nursing precautions and on proper application. It is also important to regularly monitor compliance with protocols.

Protective Outerwear

Standard protective outerwear for large animal veterinary personnel should include clean coveralls, lab coats, scrubs, or other dedicated clothing (hospital uniforms). Protective outerwear should be worn for every animal contact and should be changed regularly. This includes any time outerwear becomes visibly soiled or otherwise contaminated with body fluids perceived or known to be contaminated with potential pathogens (e.g., feces, blood, nasal exudates, urine, or uterine fluid). In addition, outerwear should be changed frequently (at least daily) because gross contamination does not need to be present for pathogen contamination to have occurred. Hospital personnel should change their hospital outerwear before leaving the building to decrease the risk of transfer of infectious agents from the hospital to the community. In order to facilitate this control measure, it is optimal from an infection control perspective for veterinary practices to provide laundry services or laundry facilities. Clothing that is potentially contaminated with biohazardous material should be handled appropriately so that personnel handling laundry are aware of the hazards and how to reduce risk of exposure.

Gloves

Gloves are an important component of barrier precautions if used properly. The CDC recommends glove use by health care workers to reduce the risk of transmission of infections from patients to personnel, to prevent health care workers’ skin flora from being transmitted to patients, and to reduce transient contamination of the skin on the hands of personnel by microorganisms that can be transmitted from one patient to another.³⁵ The same concepts apply to veterinary medicine. In certain situations glove use has been shown to be an effective means of reducing pathogen transmission in human medicine.³⁶ However, incorrect use can negate these effects, or even be harmful. Common errors with glove use include failure to wear gloves when needed, not changing gloves after contact with infectious items, touching items (e.g., pagers, cell phones, pens, medical supplies) while wearing contaminated gloves, contamination of hands or clothing while removing gloves, and failure to wash hands after glove removal.³⁷ Although gloves are used to prevent contamination of hands, the potential for inadvertent contamination through microbreaks in the glove surface or contamination during glove removal necessitates use of hand washing or application of hand-sanitizing solutions in conjunction with their use.

There are no widely accepted standards in veterinary medicine for when gloves must be used, apart from the use of sterile gloves during surgical procedures. Examination gloves that are clean but not sterile are often used when handling wounds and infected body sites and during contact with animals known or suspected to be shedding contagious pathogens. Despite relatively widespread use of examination gloves in a variety of circumstances in veterinary medicine, it is quite unusual for practices to have formal protocols regarding how and when they should be used.

Gowns

Whereas protective gowns have traditionally been used only during surgery, their use as a barrier garment when contacting high-risk patients is increasing in both human and veterinary medicine. The CDC has produced guidelines for human medicine stating that “gowns should be worn by personnel during the care of patients infected with epidemiologically important microorganisms to reduce the opportunity for transmission of pathogens from patients or items in their environment to other patients or environments.”³⁵ In general, gowns should be worn whenever direct or indirect with patients or their environment may result in contamination of caregivers’ clothing or skin that facilitates transmission of pathogens.

The ideal barrier gown would cover all areas of the body that might become contaminated, would prevent penetration of liquids, would be of adequate strength to resist tearing and puncture under normal activities, would be comfortable to wear for long periods, would be available in appropriate sizes for all personnel, would be easy to put on and remove without contamination of regular attire, would be nonabrasive to skin, would be unlikely to startle patients, and would be of acceptable cost. Unfortunately, a product with all of these characteristics does not currently exist, and facilities must prioritize the relative importance of different gown properties. This is often difficult because neither the overall effectiveness of gowning nor the effectiveness of different gowns in veterinary situations has been adequately evaluated. The problem most likely to be encountered with barrier gowns in veterinary practice is poor resistance to liquids, especially under direct contact or pressure. In large animal practice, there is a greater likelihood of contact with relatively large volumes of fluids (e.g., with diarrheic animals) or direct contact with patient surfaces that would have moist secretions or excretions (e.g., animals with nasal discharge or large infected wounds). The types of anticipated activities may also affect the required size of gown. Gowns that do not completely cover the legs and feet may be useful in some circumstances but ineffective in situations with prolonged direct contact such as with assisted neonatal nursing.

In human medicine, there are conflicting data regarding the efficacy of gowning for prevention of hospital-associated infections.^38,39 Gowns may be more effective for reducing infection of personnel. It is possible that the most significant advantage in some situations is not the protective effect of gowns or other protective outerwear, but rather the raised awareness of the potentially infectious nature of the patient, which may in turn encourage concurrent application of other important infection control practices.

Eye Protection

The use of protective eyewear, including goggles and face shields, is common in human medicine during procedures that generate aerosols or airborne droplets of blood, body fluids, and secretions.⁴⁰ Use of these items is mandated in some instances by health and safety regulations.⁴¹ Despite the current low prevalence of blood-borne zoonotic pathogens in large animal species, it would be prudent to consider the use of some type of eye protection whenever generation of aerosols from liquids or secretions that might contain contagious pathogens is likely to occur. Situations in which eye protection should be seriously considered include examination of animals with suspected viral encephalitides.

Respiratory Protection

Masks and respirators are often used to reduce the risk of exposure to infectious agents by respiratory and oral routes, to reduce the risk of contamination of patient sites with organisms from personnel, and in some situations to prevent contamination of hands with nasal or oral microflora. Standard surgical masks may be effective against the spread of large particle droplets that are transmitted by close contact and travel only short distances (up to 3 feet) from infected patients.⁴² However, the overall effectiveness of standard masks has come under debate, and some authors have questioned the overall effectiveness of surgical masks in hospital situations.⁴³

Airborne transmission of zoonotic pathogens is commonly thought to be of minimal concern in most veterinary settings, and mask use is uncommon in veterinary hospitals apart from use during surgical procedures. The actual reduction in zoonotic disease risk that might be associated with the use of surgical masks during routine patient contact is unclear. However, increased awareness of risks of specific zoonotic disease risks, and infections in immunocompromised personnel and others with special disease risks, has prompted reconsideration of recommendations regarding personal protective equipment in some circumstances. For example, although airborne transmission is not considered an important route of exposure for MRSA, hospital personnel primarily become colonized in the nasal passages, and hand-to-nose contact is frequent. Therefore mask use prevents direct contact of hand and nose, thereby decreasing hand contamination or decreasing the risk of inoculation of the nose after contamination of the hands during animal contact. Masks capable of filtering nonoily particulate aerosols with 95% capability (N95 masks) are recommended in human medicine for dealing with airborne contagions such as the severe acute respiratory syndrome (SARS) coronavirus. Although there is currently little indication that these masks are routinely required in large animal practice, it may be reasonable for facilities to at least have a plan in place to implement N95 masks if required. A critical aspect of the use of N95 masks is fit-testing and training in their use, as improperly fitted or used masks may confer little or no benefit over surgical masks.

Outpatient Areas

In general, outpatients tend to have a lower contagious disease risk, in terms of both likelihood of shedding infectious agents and their susceptibility to infectious disease. However, “lower” risk does not mean “no” risk, and it is important to design holding areas that minimize contact with other animals while clinicians obtain histories and conduct initial examinations to more clearly categorize patients relative to their contagious disease risk. Ideally, outpatients should have little or no contact with inpatient animals and minimal contact with areas visited by inpatients. However, this is often not entirely possible. For example, it is often impractical to build completely separate areas for diagnostic imaging of inpatients and outpatients. However, the general principle of separation of inpatients from outpatients should be adhered to as much as possible.

Holding stalls in admission and outpatient examination areas may need to house a large number of animals every day. Therefore it is important that a sufficient number of stalls is available to allow appropriate cleaning between use, that there are established mechanisms to allow admitting clinicians to identify high-risk cases, and that this information is promptly conveyed to relevant personnel so extra precautions can be taken with that patient and the environment with which it has been in contact. Environmental precautions may range from routine cleaning and disinfection to restricting use pending high-level cleaning and disinfection, stall cultures, or patient cultures.

Inpatient Areas

Inpatients pose greater challenges than outpatients because they often have significant risk factors for infectious disease acquisition such as comorbidity, dietary changes, antimicrobial treatment, disruption of natural defense mechanisms, surgery, and placement of invasive devices. Compromised inpatients, particularly certain patient groups (e.g., those with gastrointestinal disease) may be more likely to shed infectious agents such as Salmonella enterica. Thus, infection control protocols should emphasize the need to reduce the risk of transmission of infectious agents from inpatients to other hospitalized animals and hospital personnel, and to minimize risks related to contamination of the hospital environment. A variety of methods can be used to manage this risk; these need to be balanced with levels of risk aversion and available resources to support infection control efforts.

One method of reducing the risk of disease transmission among individuals and groups (e.g., between animals in different wards or those assigned to different services) is to assign animals to different cohorts and then create physical and procedural separation among the different groups. It is important to group animals based on known or suspected infectious disease status or infectious disease susceptibility, as well as to group and separate animals with different disease syndromes (e.g., respiratory disease or gastrointestinal disease). It is also logical to group and segregate animals that are managed by different clinical services in order to decrease the probability of transmitting infectious agents through indirect contact. As an example, because of the documented risk associated with Salmonella shedding among cattle from intensively managed populations, several large hospitals have found that it is very important to house and manage cattle separately from other large animal patients (especially horses). In general, managing inpatients as smaller cohorts helps contain transmission risk, thereby decreasing the likelihood of a widespread outbreak in the entire patient population. Creating smaller cohorts of patients with different risks for contagious disease also facilitates the use of varying levels of infection control precautions for different groups.

The design of some facilities does not allow for the separation of different cohorts in different buildings or wards. When physical separation of inpatient groups (excluding isolation cases) is impossible or impractical, animals with different disease risks can still be managed differently in a common ward system. One approach is to designate areas within large wards for different cohorts. Another is to identify animals in different risk categories, applying different levels of infection control precautions, but to allow interspersing of animals from different risk categories in the same area. Physical separation within a ward can be enhanced by use of chain or rope barricades to identify and minimize access to patients with elevated contagious disease risk status. A key for successful infection control using this type of system is the absolute need for prominent identification of different groups, having defined protocols for each group, and maintaining effective communication about disease status of these patients. One system that has been employed is the use of color labels to indicate infection control status. For example, colored adhesive dots can be placed on stalls or stall cards of all patients; red dots might indicate animals with a known highly contagious disease, yellow dots might indicate that animals are suspected of having an infectious disease or may have increased risk of acquiring infectious disease, and green dots might indicate that animals are considered to have an average or low risk of carrying or acquiring contagious disease agents. This type of system is easy to apply and easy to understand. In addition, more prominent signs can be used to more clearly indicate to all personnel certain concerns (e.g., Salmonella, MRSA, rabies suspect). One consideration with these more specific labels, however, is whether visitors could obtain confidential and sometimes prejudicial information from visible notices.

Isolation of Highest-Risk Patients

The most rigorous control of contagious disease hazards requires that transmission potential be absolutely minimized for patients suspected or known to be infected with highly contagious pathogens or pathogens associated with highly consequential diseases. In general this means that these patients should have no direct or indirect contact with other animals or areas used in routine care of patients via personnel, fomites, aerosols, or other materials. It also means that human access to these patients and their care environment should be tightly controlled. In general, in order to achieve this level of isolation, these patients will require housing in a separate, specially designed unit.

Most isolation protocols in large animal medicine focus on a limited number of pathogens. Protocols for large animal facilities tend to focus heavily or solely on S. enterica. Whether these protocols are adequate or excessive for control of other pathogens is debatable, and a broader scope is likely required in many facilities. That said, protocols that reduce the risk of transmission of one agent generally reduce the transmission potential of other agents, particularly if there are similarities regarding transmission routes or risk factors for exposure and infection.

Large animal isolation protocols need to take into consideration a variety of issues, including indicators for isolation, cleaning and disinfection protocols, protocols regarding personnel movement and barrier precautions, protocols for patient contact and movement, manure disposal, and supply stocking. Defining methods for identifying animals that need to be isolated and establishing specific criteria for handling these animals is critical, and these methods must be properly communicated to all individuals associated with patient or facility care. Developing protocols for rapid identification of patients that represent a contagious disease hazard is critical to the success of any biosecurity program. The best isolation units are not effective if unoccupied. Specific disease and syndromic criteria for isolation should be developed to facilitate prompt isolation of appropriate individuals. Isolated animals should be physically separate from the rest of the hospital population at all times if at all possible. This means that isolation units should be designed so that animals will rarely if ever have to leave the unit except for those that need an emergency procedure such as surgery. Stocks, examination areas, and scales should be available. Ideally, there should be minimal contact of personnel with isolated animals and their stall environment. The ability to monitor patients in isolation using viewing windows or by remote electronic means (e.g., web cameras, closed circuit video) facilitates the ability to deliver excellent patient care while minimizing risks associated with direct contact.

These units must be strictly managed with specific predetermined protocols in order to reliably manage the risk of transmission. Isolation protocols should be comprehensive and clearly documented in writing. Proper training of all staff, particularly lay staff who may have no background in infectious diseases and infection control, is critical. Standardized protocols for management of isolation units in human health care settings have been published by the CDC.⁴² However, similarly standardized guidelines have not been established for veterinary medicine, and protocols used at veterinary facilities are highly variable as they are tailored to specific operations and different facility and logistic resources. It is logical for veterinary facilities to consider guidelines that have been developed at other veterinary facilities and in human health care settings when developing their own isolation protocols.

In some situations, housing of potentially infectious animals in an isolation unit is not possible because of patient care issues or limitations in isolation space. As a result, consideration needs to be given to management of higher-risk patients within the general hospital environment. This can be done in a few different ways, including grouping of general risk groups and application of intermediate isolation techniques to patients that are considered at higher risk for being infectious but that are not deemed candidates for housing in an isolation unit. In-hospital isolation protocols allow for an increased level of protection but are not a replacement for a proper isolation unit and should not be used solely for clinician convenience. Protocols should be developed regarding the handling of animals, the stall, and the area around the stall. Animals that are isolated in the hospital should not leave stalls unless they are being moved for required procedures. If movement is necessary, feet should be cleaned and disinfected using appropriately diluted chlorhexidine solutions. The potential for environmental contamination can be reduced by having a person follow the animal with a bucket to collect any feces that may be passed during transit. Traffic areas should be promptly cleaned and disinfected. Protective barrier clothing such as full waterproof coveralls or full-length waterproof gown, gloves, and dedicated footwear or boot covers should be worn for any contact with the patient or its environment. The area around the stall entrance should be considered potentially contaminated and disinfected routinely (at least three or four times per day). Disinfectant footbaths or footmats used at stall doors can reduce bacterial contamination of footwear.^44,45 Attention should be paid to the pattern of water drainage from the stall and in the area. If water runs from the stall to the breezeway or runs down the breezeway past the stall, then housing of potentially or known infectious animals in the stall may be inappropriate. Animals should not be allowed contact with neighboring animals. Barriers may be required if solid walls are not present on all sides. Specific protocols should be developed for cleaning in-hospital isolation stalls. These stalls should be cleaned last, personnel cleaning stalls must wear protective gear, and items used to clean the stall must be disinfected immediately after use.

Isolation guidelines for human medicine target the prevention of five different types of transmission: contact transmission, droplet transmission, airborne transmission, common vehicle transmission, and vector-borne transmission.⁴²

Surveillance Options and Strategies

Theoretically, an optimal surveillance system would allow real-time detection of every occurrence of nosocomial infection. However, pursuing this goal would be unrealistic for reasons of practicality and would be an inefficient use of resources. Although all nosocomial infections are important relative to patient well-being, some are more important than others. This is because the impact on patient health is much more significant for some diseases, and also because highly contagious diseases are more likely to affect a larger number of patients. Focusing surveillance on these high-impact nosocomial infections is logical, as a greater proportion of these occurrences are also likely to be preventable in comparison with more sporadic problems. Furthermore, experiences with infection control in human health care settings have shown that it is possible to be more efficient with infection control and just as effective if special high-risk or high-cost problems are targeted.

Determining which specific nosocomial infections were likely preventable is a difficult and potentially contentious task. Rather than focus on individual infections, infection control efforts in human hospitals have benefited by focusing on comparing rates of infection and estimating the proportion that might be preventable by referencing some accepted standard. During the past 30 years, human hospitals have made great efforts to characterize rates of nosocomial infection that can be expected even under the best of circumstances. By estimating rates for these “nonpreventable” infections, it has then been possible to identify hospitals with higher than average rates for nosocomial infections. Because of the tremendous differences among hospitals and among patient populations, it has become standard to focus on more restricted, high-risk patient groups for which there is better comparability (e.g., neonatal or cardiac intensive care patients). It is also far more feasible to perform surveillance for nosocomial surveillance in these high-risk patient subgroups than it is in the larger general population, which has a much lower risk of nosocomial infection. Performing surveillance with standardized case definitions over time allows identification of specific risk factors, which could then be used to prospectively refine management of patients (e.g., a high-risk patient could be identified and be subjected to more aggressive control measures as a preventive strategy). Unfortunately, there is very limited information available regarding rates of nosocomial disease that can be found at individual hospitals, let alone estimation in multiple hospitals, which would be required in order to obtain interhospital comparisons that would be useful in identifying latent problems at specific facilities. Although making standardized comparisons among hospitals would require tremendous cooperative effort, individual facilities could make significant progress in identifying important changes in nosocomial infection rates if efforts were made to benchmark their nosocomial infection rates over time.

When designing a formal surveillance effort to aid infection control programs, it is important to tailor efforts to a specific facility or practice. There is a wide variety of design possibilities for hospital surveillance systems, and the specific focus and methods should be carefully matched to the needs and resources of each establishment. Diseases that are the highest priority for surveillance must be specified, along with standardized case definitions that will be used to identify these cases. Efforts may target nosocomial disease related to specific procedures or organ system involvement, or just as commonly they may target specific infectious agents of interest. For example, systems might be established to look for surgical or intravenous catheter site infections, methods may target surveillance for respiratory tract infections, or efforts may specifically target detection of Salmonella or MRSA infections. It must also be determined whether clinical disease will be the outcome of interest or whether it is important to look for animals with subclinical infections. This will generally vary by disease and likely will be determined by the natural history or pathophysiology of the disease (e.g., Does shedding occur in the absence of clinical signs? Is there a chronic carrier state? What are the risk factors related to the likelihood of shedding?). Furthermore, if clinical disease is the outcome of interest, it is important to consider whether the case definition will include some type of confirmation of the cause or whether diagnoses will be more based on clinical signs and syndromic in nature (e.g., surgical site infections could be defined based on recovery of a bacterial agent in the presence of clinical disease, or they could be defined solely on the presence of a predetermined combination of clinical signs such as erythema and drainage). As discussed previously, another consideration is whether surveillance will target specific subgroups of the population or whether it will include all patients. The major benefit of targeted surveillance is that it decreases the cost and effort of data collection, but the tradeoff is the inability to detect potential problems in the patients that are not being monitored. However, increasing awareness about infection control methods for common or more important diseases generally has the effect of increasing awareness and compliance with control measures that relate to other potential nosocomial problems. It also must be determined whether surveillance will be active (i.e., patients with nosocomial problems will be actively sought out) or whether passive surveillance (i.e., reporting is voluntary) is acceptable and appropriate. In general, active surveillance will be used only in targeted subpopulations and only to look for more common and more important diseases, and syndromic surveillance should be more heavily relied on when the targeted population is larger or as a supplement to culture or etiologically based surveillance efforts.

Another important consideration is how data will be gathered for this effort. Significant personnel compliance is needed for active culture-based surveillance of large numbers of patients. Similarly, any type of chart review system for benchmarking expected rates of nosocomial disease requires a significant time commitment. Surveillance efforts are greatly aided by the ability to use computer-based search mechanisms, and it is strongly recommended that any practice use electronic medical record systems to maximize the ability to perform surveillance. For example, something as simple as being able to monitor the number of febrile or leukopenic patients on a daily basis could be extremely powerful as an aid to infection control efforts. Even financial databases can be useful in surveillance efforts. For example, financial databases may be very useful for surveillance for benchmarking antimicrobial prescriptions or specific procedures, such as intravenous catheterization or surgeries.

Monitoring for bacterial contamination of the hospital environment has been a useful adjunct to patient monitoring in comprehensive biosecurity programs at veterinary hospitals.^20,46,47 In addition, in some situations, such as when attempting to control ongoing outbreaks, there is no substitute for culturing the hospital environment to detect important environmental reservoirs.^10,48 Use of electrostatic household wipes has been extremely useful for sampling to detect S. enterica in routine surveillance as well as in the face of outbreaks.

As an alternative to culturing environmental samples for one specific agent, it may be useful to enumerate total numbers of bacteria recovered from hospital surfaces using either swabs or contact plates (e.g., RODAC).^16,47 Contact plates are simple to use, require minimal investment of labor, and when used on regular basis can provide valuable information regarding cleanliness of hospital surfaces. Such data can be used as feedback for the cleaning personnel, for monitoring of quality of cleaning, or for pinpointing problem areas. It is important to remember that bacteria can be recovered from most surfaces, even in the cleanest of hospitals. Therefore, in order to be most meaningful, if quantitative environmental cultures are to be performed they should be repeated on a regular basis in order to establish meaningful baseline values for comparison.

The use of rapid and sensitive diagnostic tests is particularly important for the management of highly contagious diseases. Polymerase chain reaction (PCR) and antigen detection tests, which can be much more rapid than traditional culture systems for bacteria and viruses, have become more widely used for both patient and environmental surveillance efforts. However, these tests cannot fully replace culture-based assays, because analysis of microbes is essential to fully understand the epidemiologic implications of each recovery. For example, if on a single day three patients were found to be shedding Salmonella using PCR assay, it would not be possible to know whether these were unrelated events. In contrast, if shedding were detected using culture and the Salmonella isolates were then shown to be from different serogroups, this would make it unlikely that shedding was related to nosocomial exposures from a single source. In some situations it may be logical to use both rapid and culture-based assays to maximize both speed and ability to perform epidemiologic investigations. Availability of qualified laboratories, rapidity of testing, and costs will all have to be considered and balanced in these considerations.

Monitoring Personnel Compliance

Success of an infection control program is absolutely dependent on corporate participation that arises from a well-developed sense of responsibility among individuals. Actively engaging all personnel in biosecurity programs becomes increasingly difficult as organizations become larger and more complex. Unfortunately, the most cautious actions of a majority of personnel can be for naught if even one individual neglects to take appropriate precautions under just the right (wrong) circumstances. Although it is very important for administrators to engage in surveillance to detect systematic noncompliance with policies, it is just as important to empower all personnel and expect them to participate in monitoring for individual acts of noncompliance. Remembering that most noncompliance arises from a natural tendency for people to revert to the most convenient practices (which are not necessarily the most “safe” from the biosecurity perspective), it is important to couple surveillance efforts with education so that all personnel fully understand why they are being inconvenienced. In addition, providing useful feedback and communication about issues that arise in the hospital will help to reinforce the need for compliance. For example, monitoring and reporting of bacterial shedding or environmental contamination detected as a part of surveillance programs can help to keep hospital personnel aware of the potential hazards of reduced biosecurity efforts.

Measurements Related to Health and Disease

Although outcomes for individual animals may be the most important bottom line for many clinicians, it is important to remember that infection control by its very nature often has a larger population-based perspective. Therefore, although diagnostic tests results have great relevance for an individual animal, a positive test result may not have great value for the entire population unless it is interpreted contextually. As such, it is critical to remember that some type of denominator information is needed in addition to numerators to provide relevance over time or for different subpopulations (e.g., numbers of all infections, numbers of animals tested). Some examples of relevant denominators include patient admission totals for a given period, patient-days of hospitalization, procedure events such as surgeries or catheter placements, and culture totals.

Developing a Comprehensive Surveillance Strategy

As mentioned, it is unrealistic to expect to detect all occurrences of nosocomial infection or all animals shedding agents of interest through any hospital surveillance system. Rather, veterinarians should work toward developing strategic surveillance programs that will allow reliable estimation of rates for important events if they occur with any significant frequency, as well as rapid detection of “unexpected” important events. It is likely that a mix of strategies described earlier will be used for the various agents and disease problems. For example, if S. enterica shedding occurs at some low-level yet regular frequency in a hospital (e.g., 3% of all hospitalized equine patients) and it is considered an important potential hazard for other patients, it is reasonable for an active surveillance program to be developed that allows detection of clinical and subclinical shedding of Salmonella as a patient management tool and also allows detection of important trends over time so that nosocomial outbreaks could be rapidly identified and stopped. In contrast, Clostridium difficile and Clostridium perfringens may not have been detected with any regularity in patients at a particular hospital or may be more difficult to actively monitor because of available testing methodologies, yet they may still be considered important because of their significance as pathogens and their potential for contagious spread. For these pathogens, it may be more reasonable to use a reliable passive surveillance strategy to call attention to patients when clinical signs or culture results indicate that these agents may be present. In addition, maintaining some level of surveillance for compliance with infection control procedures and policies is necessary to ensure that a biosecurity program is functioning properly.

Written Protocols

The first step to ensuring that necessary information is disseminated to all personnel is to document policies and protocols in writing. This effort is valuable for all veterinary practices but is especially critical in larger and more complex veterinary hospitals. This relatively simple step has many benefits. First, documenting procedures requires a thorough review, which by itself is beneficial. Second, documenting policies and protocols in writing imbues the infection control program with a sense of purpose and commitment. Third, documenting procedures helps to ensure consistency in application by all personnel as well as over time. As discussed, all infection control procedures are inherently inconvenient, and the natural tendency is for personnel to drift toward more convenient ways performing activities, which may not provide an adequate degree of protection against nosocomial infections. Fourth, documented policies demonstrate a degree of due diligence, which is useful from a legal liability standpoint relative to the occurrence of nosocomial or zoonotic infections.

Once these protocols have been documented, it is important to require their use as a reference and to make a specific effort to educate personnel about the policies and procedures. A written document serves no purpose if it is not used. Veterinarians and other personnel are busy people, and the immediacy of caring for patients and clients can easily overwhelm seemingly mundane tasks such as studying written protocols. A valuable aid in this process is to have some type of training program. This does not necessarily mean formal presentations; it is valuable to organize a meeting of all personnel for the sole purpose of discussing infection control issues. Although this seems logical, biosecurity training is not a universal occurrence even in teaching hospitals. In a survey of teaching hospitals from American Veterinary Medical Association (AVMA)–accredited institutions, only 15 of 37 responding institutions reported that they required that personnel (students, technical staff, veterinarians) participate in some type of formal training program regarding infection control and biosecurity, and only seven of these institutions provided more than a single training exposure.⁴⁹

Training Programs

It is also important to consider the differences in training and experience among personnel. By their nature, infection control programs are dependant on adherence to important protocols by all personnel regardless of their position description. Nonveterinarians are invaluable members of most veterinary practice teams, and even personnel who might never touch patients but instead are employed as receptionists or for the single specific task of cleaning are absolutely critical for the success of infection control programs. Veterinarians sometimes underappreciate how their specialized training has provided them a broad appreciation for basic principles of contagious disease transmission and control. Without the experiences of a veterinary education, many personnel do not have the same basic understanding of contagious diseases. Simply telling people to follow certain rules leads to inevitable compliance problems. Although it is important for people to know what is expected of them, it is just as critical for them to know why these procedures are important. Without a thorough understanding of why inconvenient infection control practices are needed, they will inevitably be discarded over time as seemingly illogical. To help ensure uniformity of exposure among all personnel, some hospitals have developed training documents and require that new employees pass a written evaluation before they are permitted to begin work.

Another important aspect of education and awareness is to instill a need to lead by example and to empower all personnel to hold anyone else in the practice accountable for his or her actions. The hierarchy in authority that is needed in the delivery of patient care (veterinarians at the top of the hierarchy, personnel without formal training at the bottom) can interfere with optimal infection control. A common non sequitur related to infection control is that those with the most training can be the persons least likely to adhere to important policies. This is true both in human and veterinary medicine, as has been repeatedly shown relative to hand hygiene.²¹ Physicians and residents have been shown in numerous studies conducted in a variety of settings to be significantly less likely than nurses to adhere to appropriate hand-hygiene protocols. Observations in the veterinary setting suggest that the same trends are true for hand hygiene, as well as for appropriate use of barrier nursing precautions. All people pick up cues for behavioral expectations from their surroundings. If personnel who clearly understand the importance of preventive measures such as hand washing (physicians and veterinarians) fail to routinely follow best infection control practices, there is little hope that trainees and laypersons will routinely trouble themselves to habitually use an important albeit inconvenient practice. Furthermore, it seems that the more respected the position a person holds in a practice, the more likely it is that individual acts of noncompliance will influence the actions of others. Students in teaching hospitals can watch classmates correctly follow infection control policies throughout the day and yet can be more influenced to be noncompliant by observing the single time that a senior clinician ignores a practice guideline.

One way to improve compliance and counter these influences is to use disseminated enforcement by actively encouraging all personnel to call attention to noncompliance. Once it has been determined which procedures are required for a particular situation and this has been documented, there is no reason that nontechnical staff should be any less capable than a veterinarian in determining whether a procedure has been correctly followed. It is important that this community enforcement be empowered by all in a spirit of friendly camaraderie and team building. Some hospitals have noted significant improvements in compliance using this method of enforcement and have even used competitions between “teams” with the incentive of agreeing that the loser must pay a reward to the other team (e.g., pizza lunch).

Zoonosis Awareness

One of the most important objectives for an infection control program is to protect personnel and clients from illness associated with zoonotic infections. This is another area in which veterinarians sometimes forget that not all personnel have an understanding of hazards or of how to take appropriate actions to protect themselves. Without this knowledge, personnel may take inappropriate risks or may overreact to perceived hazards in what is actually a low-risk situation. In addition to holding briefings or question-and-answer sessions, it is wise to provide a good resource text, written summaries, or URL addresses of reliable Internet resources so that personnel have tools available to help them research answers to their questions. Table 46-2 provides a brief summary of some zoonotic pathogens that might be transmitted from domestic large animals through occupational activities of veterinary personnel.

Table 46-2 Zoonotic Diseases of Domestic Large Animal Species That Are Transmissible through Occupational Exposures to Veterinary Personnel*

Personnel with Increased Risk of Infection

An important area for which there is not much published literature relates to risks for zoonotic infections in personnel who have an increased susceptibility to infectious diseases or those in whom the consequences of clinical infection may be particularly severe. Obviously there is an overall increase in risk of infection for immunocompromised personnel, but there is very little specific information about which disease risks might be of greatest importance to this population. In addition, it is essentially impossible to predict which agents are of little risk to people with a healthy immune system but may be of much greater risk to immunocompromised personnel. Individuals being treated orally with antimicrobial drugs are generally considered to have an increased risk for infections with enteropathogens, so it is prudent for personnel being treated with antimicrobial drugs to be especially attentive to protocols related to personal protection. Pregnant women have a special risk for infections that can result in fetal infections or abortion and should therefore employ practical precautions that reduce the likelihood of infection. In general, paying strict attention to good hand-hygiene protocols, routine use of gloves to reduce the likelihood of contact exposures, regular use of protective outer garments or hospital dedicated-attire, and avoiding eating and drinking around animals or in their environments should help to reduce the likelihood of exposure to potential zoonotic pathogens.

Salmonella

S. enterica is the agent most commonly reported in association with nosocomial disease outbreaks and closure of large animal hospitals. In a recent survey of teaching hospitals from AVMA-accredited institutions, 31 of 38 responding institutions (82%) reported documenting outbreaks of nosocomial disease during the previous 5 years and 65% of institutions reported S. enterica as being associated with an outbreak (20 of 37).⁴⁹ Additionally, most of these institutions (17/20) had to restrict admissions to reduce patient risk or mitigate contamination, and 11 of these institutions closed at least part of their facilities completely. All species are susceptible to infection, but hospitalized cattle from intensively managed populations generally have the highest prevalence of shedding and camelids the lowest. The likelihood of shedding in patients while hospitalized is greatly influenced by the prevalence of infection in animals at home premises. A notable number of patients shed Salmonella without evidence of associated illness, but patients are significantly more likely to shed if they are systemically ill. This is especially true if animals show signs of gastrointestinal illness. Numbers of organisms shed per gram of feces are generally much greater in clinically affected animals. Animals known to be infected with Salmonella should be managed in isolation with strict barrier precautions and hand-hygiene protocols. Shedding tends to be more commonly detected in the summer and fall and may also be generally more common in warmer climates. Although nosocomial outbreaks are usually detected in association with the spread of clinical disease, subclinical infections can be more common than clinical infections during outbreaks. Zoonotic infections in veterinary personnel have been commonly detected in association with nosocomial outbreaks. There is apparent variability among strains with regard to virulence, infectivity, and ability to persist in the environment, and this strain variability may be a very important determining factor regarding nosocomial outbreaks of infection. Environmental contamination near infected patients is the rule rather than the exception, and active surveillance has shown that contamination can become disseminated to quite distant areas of the hospital from only a single infected patient. In one study 12% of 452 environmental samples collected over 10 weeks in a nonepidemic period using electrostatic household wipes were positive for Salmonella.⁴⁶ Experience has shown that environmental contamination is even greater during outbreaks. In nonepidemic situations there tends to be great variability in phenotypic markers (serogroup, serotype, and antimicrobial susceptibility) among isolates recovered from patients over time, which often makes it possible to differentiate isolates in epidemiologic investigations. In other situations, especially when certain strains are circulating actively in the region of a hospital, use of genetic analysis may be necessary in order to differentiate strains of Salmonella for purposes of epidemiologic investigations. Culture methods used in diagnostic laboratories are highly variable, which can significantly affect assay sensitivity. Veterinarians should seek out laboratories that are known to have optimized culture methods for use in diagnostic situations. PCR assays for Salmonella are available commercially at a number of laboratories. However, because of the importance of phenotypic and genotypic comparisons of isolates that are conducted as part of epidemiological investigations, PCR assays are not recommended for regular use in surveillance programs without parallel analysis using culture. Active surveillance programs are commonly used in large hospitals as a management tool to detect clinical and subclinical infections in large animal patients. In addition, environmental surveillance is sometimes used as an adjunct to detect environmental contamination. All common disinfectants are effective against Salmonella organisms under optimal conditions. However, its common association with fecal material, other organic matter, and dirt necessitates careful adherence to good cleaning (physical disruption of surface matter using detergents) and disinfection procedures in order to minimize the likelihood of environmental persistence. Mitigation in response to nosocomial outbreaks requires thorough decontamination of all environmental surfaces, which may be possible only after closure to new admissions, although disinfectant misting may be a useful alternative in some situations.⁵²

Clostridium difficile

Although less commonly implicated with diarrheic disease than S. enterica, C. difficile is a potentially important nosocomial pathogen in horses. C. difficile should be considered as a differential diagnosis in horses with diarrhea and duodenitis-proximal jejunitis. Standard infection control methods used for salmonellosis should be adequate to control transmission of C. difficile, with the exception of disinfection. Because C. difficile is a spore-forming bacterium, disinfection can be difficult. Clostridial spores are highly resistant to environmental degradation, and most disinfectants that kill Salmonella are ineffective against bacterial spores, with the exception of bleach (hypochlorite solutions). Accelerated stabilized peroxide and peroxygen disinfectants may also be effective, although less information is currently available. An additional, albeit mostly unsubstantiated concern is the potential for zoonotic transmission of C. difficile from horses or cattle to humans. The strains of C. difficile isolated from animals are often indistinguishable from those that cause disease in people. Therefore, animals infected with C. difficile should be considered as potential sources of zoonotic infections in humans.

Cryptosporidium parvum

Animals of all ages in a variety of host species have been shown to shed C. parvum oocysts, but the shedding prevalence is much greater in young animals, and the primary infection control hazard involves shedding by diarrheic neonates, especially calves. This is because of the extraordinary numbers of oocysts shed by affected young animals, the small infectious dose, and the hardiness of organisms. Affected calves can shed more than 10⁷ oocysts per gram of feces during peak shedding, whereas humans and other animals can be clinically infected with fewer than 100 oocysts, although there does appear to be some difference among individuals and also among strains. To further complicate control, oocysts are profoundly resistant to all disinfectants that can be regularly used in hospitals. Research has shown there are different lineages of C. parvum that relate to host range; genotype 1 appears to infect only humans, whereas genotype 2 (sometimes called bovine genotype) infects a wide variety of other species, including domestic large animals and humans. Cryptosporidiosis is an important zoonotic disease hazard in veterinary personnel, and there are a number of documented outbreaks involving animal caretakers. Cryptosporidium is considered to be a relatively common nonviral cause of self-limiting diarrhea in immunocompetent persons, particularly children. Clinical disease can be severe and even life-threatening in immunocompromised persons. Diarrheic neonates can be easily and inexpensively screened using direct microscopic examination of fecal smears prepared with acid-fast stains. Regardless, it is very prudent to house diarrheic neonates in isolation and handle with strict barrier precautions and hand-hygiene protocols. Personnel cleaning these housing areas should avoid using high-pressure water, to minimize the risk of aerosol and droplet exposure. This is complicated by the resistance of coccidian parasites to disinfectants, which necessitates the reliance on vigorous scrubbing with soap and rinsing with copious amounts of water in decontamination efforts. The likelihood of inadvertent oral exposure while cleaning can be reduced by using face shields or N95 disposable masks along with gloves.

Equine Rotavirus

Although outbreaks of rotavirus are not uncommon on breeding farms, outbreaks in veterinary clinics are rare. Equine rotavirus is of most concern in facilities with a large neonatal caseload. Rotavirus may be shed in the feces of affected foals, clinically normal foals, and adult horses. Therefore prevention of exposure is difficult. However, it is likely that clinically affected foals are the most common source of infection, through direct contact or common vehicle exposure. As a result, isolation of affected animals and the use of barrier precautions are the most important infection control measures. With the exception of disinfectants, protocols directed at control of S. enterica should be adequate for rotavirus control. Little specific information is available regarding the relative effectiveness of different disinfectants on equine rotavirus. However, as a nonenveloped virus, equine rotavirus should be expected to be resistant to environmental degradation and many disinfectants commonly used in veterinary medicine. The use of phenolics has been recommended because of their better activity in the presence of organic debris. Oxidizing agents probably have similar effectiveness and may be preferable because they have a much lower potential for toxicity.

Bovine Viral Diarrhea Virus and Border Disease Virus

The closely related members of the genus Pestivirus are not commonly considered nosocomial disease hazards, but this may be more because of a lack of detection than a lack of occurrence. The main infection control hazard is related to exposure of susceptible pregnant cattle, sheep, goats, or camelids to persistently infected animals that continuously shed large amounts of virus. The long period between infection of pregnant females and the birth of affected offspring complicates the ability to make relevant observations about the frequency of nosocomial infections. Therefore it may be important to encourage or require vaccination of valuable pregnant cattle or alpacas before admission. In addition, animals known or suspected to be persistently infected should be managed in isolation with barrier precautions to minimize transmission. This includes neonates showing signs of congenital infection. Increased biosecurity precautions should also be used with animals from herds with a recent history of disease related to these viruses. Direct contact with persistently infected animals is an efficient method of transmission, but limited research shows that calves can be infected through contact with contaminated stalls and through droplet or aerosol exposure over a distance of at least 1.5 m.⁵³ Appropriate use of cleaning and disinfection methods should readily decontaminate the environment.

Strangles (Streptococcus equi equi)

An important aspect of S. equi control is identification and management of subclinically infected animals. Syndromic guidelines for isolation on admission (e.g., isolation when patients are admitted from farms with recent a history of clinical S. equi infections, or isolation of horses with fever of unknown origin or unexplained nasal discharge) can help in managing potentially infectious horses so that they can be isolated pending the results of screening. The ubiquitous nature of S. equi and the possibility that essentially any hospitalized horse could be a subclinical carrier means that there is an ever-present, if low, likelihood of S. equi introduction into the hospital environment. Experience suggests that routine universal screening of horses admitted to veterinary hospitals is not necessary to control nosocomial S. equi infections. However, screening and isolation of horses from farms with endemic S. equi would be a reasonable control strategy. Standard infection control measures, including preventing direct contact of hospitalized animals, optimizing hand hygiene, and using appropriate cleaning and disinfection, should be useful for reducing the risk of S. equi transmission should a colonized horse be admitted. Vaccination in the face of an outbreak with vaccines that are currently available is not recommended because of a lack of proven efficacy and concerns regarding development of purpura hemorrhagica. There is also no evidence of a need to require vaccination of elective cases before hospital admission. S. equi is susceptible to all routinely used disinfectants, when used properly.

Equine Influenza

Influenza is one of the most contagious diseases affecting horses. Immunity is transient, and horses can be repeatedly affected during their lifetime. There is no carrier state, and maintenance in a population is dependant on transmission from one acutely infected horse to another. In horse populations aggregated at racetracks, shows, or other venues, attack rates can reach 15% to 30%.⁵⁴ The incubation period from exposure to onset of clinical signs is typically about 2 to 4 days, which commonly coincides with the onset of virus shedding. Horses are often febrile and obtunded at the onset of disease. Paroxysmal coughing is a classical sign of influenza infection that develops in some horses as disease progresses. Because of its contagious nature, identification of multiple acutely febrile horses can be an early indication that influenza virus is spreading in the population. Rapid identification and confirmation of animals shedding virus allow initiation of efforts to minimize contagious spread. Antigen detection assays are commercially available and very useful for rapid confirmatory testing (e.g., Directigen Flu A, BD Diagnostic Systems). However, these assays have limited sensitivity; virus shedding was detected in only approximately 30% of clinically affected horses during outbreaks using this assay, and so tests should be performed on multiple horses and interpreted in the aggregate for the population.⁵⁵ Negative test results for individual samples should be interpreted with caution because of the consequences associated with not using appropriate control measures during an outbreak of a highly contagious disease. PCR tests are available and may be more sensitive than antigen detection assays, but published validations of these assays are generally unavailable. Virus can be transmitted through aerosol, droplet, and contact transmission and can easily be transmitted over several feet in respiratory aerosols generated by coughing horses. Therefore horses confirmed to be infected should be managed in complete isolation with full barrier precautions, paying strict attention to hand-hygiene protocols. Influenza virus can survive on surfaces at most for a few days in a cool, moist environment. As an enveloped virus, influenza is susceptible to damage from extreme environmental conditions and is readily inactivated by all common disinfectants if they are properly applied. Although clinically affected animals are the most likely to shed large amounts of virus, in unaffected horses sampled during large outbreaks, seroconversion and virus shedding can be found in about 30% and 5% of the exposed populations, respectively.^54,55 Therefore it is prudent to increase infection control precautions for all exposed but apparently unaffected horses in order to minimize risks of transmission. Early vaccination of all horses with intranasal vaccine may be of value in abbreviating the course of an epidemic. If new admissions are allowed when there is an elevated risk of influenza virus infection, horses should be required to have been recently vaccinated before admission (preferably a minimum of 2 weeks before admission) with vaccines having proven efficacy. Regardless of vaccination history, it is unwise to admit very young or immunocompromised horses when there is an increased risk of infection with influenza virus.

Equine Herpesviruses

Equine herpesvirus (EHV) types 1 to 5 are ubiquitous in horse populations and are highly contagious. EHV-1 and EHV-4 are the most widely recognized as important causes of outbreaks of disease in horses, and nosocomial transmission of both agents has been noted. EHV-4 infections are associated with contagious respiratory disease that principally affects horses under 3 years of age. EHV-1 infections are associated with respiratory disease, neurologic disease, acute to peracute pulmonary vasculitis, and abortion. Immunity is relatively short-lived, and infections are likely to occur throughout the life of horses. Many if not most of these infections are undetected or occur with only mild clinical signs. The most common clinical sequela of infection is mild respiratory disease during the first 2 years of life. Infrequently, EHV-1 infections can result in more severe complications such as abortions in pregnant mares or paralysis. All EHV-1 and EHV-4 infections originate in the respiratory tract, but epidemiologic evidence suggests that contact and droplet transmission between horses in relative proximity is much more common than aerosol transmission over greater distances. Fever is commonly the initial clinical sign exhibited by infected horses, and identification of multiple acutely febrile patients can be an early indication of nosocomial spread of EHV in the population. Most horses can be shown to be latently infected with EHV-1 and EHV-4 by the time they reach adulthood, and subsequently any hospitalized horse might serve as a source of infection for other patients by recrudescing virus in response to stresses of disease, hospitalization, and transport. However, clinical experience suggests that nosocomial spread most commonly originates from clinically affected horses. Therefore, rapid identification of animals suspected of being infected, isolation of affected horses, and use of barrier precautions with appropriate hand-hygiene protocols are generally effective for minimizing the risk of nosocomial transmission. All horses exhibiting ascending weakness, paresis, or paralysis should be suspected of having EHV-1 infection and managed in isolation until they can be proven to have stopped shedding or another diagnosis is confirmed. Herpesviruses are enveloped viruses, and routine cleaning and disinfection procedures should be adequate for decontamination of surfaces, assuming appropriate protocols are followed. PCR testing of nasal secretions is the most useful assay for rapid confirmatory testing. Serial testing is useful for establishing that shedding has stopped. Without adjunctive testing, infected horses should be quarantined for a minimum of 28 days after cessation of disease. Using serial testing as a confirmatory adjunct, this quarantine period might be shortened to 14 days after cessation of disease. However, experimental infection studies have shown that shedding can be intermittent, and negative test results must be interpreted with caution.

EHV-3 is less commonly regarded as a nosocomial problem but has been noted to be spread through contact with contaminated materials during reproductive procedures as well as between horses during coitus. Therefore it is a notable hazard for practices that specialize in reproductive services. EHV-3 causes coital exanthema, a pustular disease affecting the vulva and vagina of mares and the penis and prepuce of stallions. Appropriate cleaning and disinfection of materials used in reproductive examinations, avoiding use of examination sleeves and gloves with multiple horses, and rigorous adherence to sound biosecurity precautions for breeding populations should control spread of EHV-3. The prevalence of latent EHV-3 infections is not well documented. Recently, evidence associating respiratory disease in young horses and EHV-2 or EHV-5 infection has been published,⁵⁶ but the significance of these agents in the occurrence of nosocomial disease is unknown.

Methicillin-Resistant Staphylococcus aureus

MRSA is emerging as an important veterinary and zoonotic pathogen. In large animals, MRSA infections have been most commonly identified in horses and pigs. Transmission of MRSA between these species and attending personnel can occur, and MRSA colonization and infection appear to be an emerging occupational risk associated with large animal veterinary practice. Transmission of MRSA is thought to mainly occur through direct or indirect contact between infected or colonized people or horses and hospitalized horses. Despite the potential for respiratory tract colonization, the potential for droplet and airborne transmission is minimal. The largest nosocomial infection problem related to this pathogen in large animals has been associated with the infection and colonization of equine patients. Infections are principally noted at surgical sites and wounds, whereas colonization predominantly occurs in the nasal passages, although gastrointestinal colonization has also been noted. If not identified by active surveillance, colonized horses can be silent yet prolific reservoirs for infection of humans and horses. Prevention of MRSA transmission requires careful attention to practices that prevent contact and common vehicle transmission, including use of good hand-hygiene practices, restriction of horse contacts and isolation of infected or colonized animals, and use of specific measures aimed at identifying carriers. All colonized or infected horses should be treated as infectious, housed in isolation, and handled with strict attention to contact barrier precautions. Screening by culture of nasal swabs collected at the time of admission can help control MRSA in areas where it is endemic in the community or the horse population. Screening of personnel may be required periodically if there is epidemiologic evidence of nosocomial transmission or zoonotic infections. Personnel screening can be a difficult and contentious area, so it is wise to develop screening guidelines in advance of an outbreak.⁵⁷ S. aureus is susceptible to most disinfectants, if used properly.

Coxiella burnetii

Coxiella burnetii is the causative agent associated with Q fever. Although most infections in humans are subclinical, personnel that contact livestock have a greater risk of infection, and disease can be severe and even fatal in a small portion of cases. It is also highly infectious, has a low infective dose, and can be transmitted through contact as well as by droplet and airborne routes. C. burnetii can be found in a variety of animal species, but zoonotic transmission is most commonly associated with periparturient ruminants (especially small ruminants). Serum antibody tests, antigen detection assays, and PCR assays can be used to identify infected animals, but the sensitivity of these assays has been questioned. Because of the potential significance of clinical infections in humans, all attending personnel should be appropriately aware of the zoonotic potential and risks associated with Q fever. The risk of serious clinical consequences should noted in particular by pregnant women and people with valvular heart disease or immunosuppression. Medical histories for individuals and flocks should be considered to determine if there is an indication that C. burnetii may be a greater than average risk. Biosecurity measures that could be used to minimize hazards to people with a high risk of clinical infection include isolating periparturient small ruminants, paying strict attention to hand-hygiene protocols, and using respiratory protection and barrier nursing precautions when handling potentially infected animals. Particular care should be taken during parturition and when handling aborted fetuses and newborn small ruminants. For animals known to infected, care should be used when cleaning and disinfecting stalls or other housing environments, and contaminated bedding and other materials should be handled with caution.

Antimicrobial Resistance and Drug Use

Although antimicrobials are undoubtedly required for proper management of a significant percentage of hospitalized large animals, it is reasonable to consider whether antimicrobial resistance and antimicrobial drug use affect the occurrence of or the ability to control nosocomial infections. The first relates to outbreaks of nosocomial infections with bacteria that are resistant to multiple antimicrobial drugs. These outbreaks are not extremely common but are a noted occurrence in human and veterinary hospitals and often occur in association with care in specific hospital units such as a critical care or surgery facility. Agents frequently identified in association with these outbreaks include enteric organisms such as E. coli and enterococci, skin commensals such as S. aureus, and Pseudomonas and other bacteria. Significant research into these organisms has identified specific strains and even specific genes that are commonly identified in association with agents responsible for these outbreaks (e.g., MRSA, vancomycin-resistant enterococci [VRE], bacteria with extended spectrum β-lactamase resistance). The role of antimicrobial use in specific patients or even in specific hospitals in promoting the occurrence of nosocomial outbreaks is not always conclusive. However, some experimental evidence does show that treatment with a specific antimicrobial drug is associated with an increased propensity for shedding of bacteria that are resistant to analogous drugs.⁵⁸ Therefore common use of a particular drug within a hospital could apply selective pressure that more generally promotes colonization with resistant bacteria,⁵⁹ or it could enable or promote the survival of specific bacterial strains capable of causing nosocomial epidemics (e.g., VRE and MRSA). These concerns are supported by specific documentation that antimicrobial drug exposure can be associated with increased likelihood of shedding of enteropathogens^60,61 and multidrug resistant pathogens.⁶² In addition, antimicrobial drug exposure is a recognized risk factor for colitis in horses, which can be one of the most important infection control concerns in large animal facilities. Therefore efforts to reduce antimicrobial use and ensure logical (prudent) use can be beneficial to the individual patient and other hospitalized animals, in addition to addressing the more abstract concerns about emergence of antimicrobial resistance.⁵⁸ Surveillance aimed at benchmarking the use of antimicrobial drugs over time, or to monitor use for specific conditions or in specific circumstances (e.g., outside of regular hours), may be useful for guiding policy decisions, but it is not useful for identifying specific occurrences of “imprudent” use. Of greatest importance is education so that all individuals with prescribing power understand the issues and the reasons for careful antimicrobial use. Measures such as developing selection algorithms for patients with specific types of disease and restricting the use of certain drug classes (e.g., glycopeptides) have been used by some facilities and may decrease the likelihood of some occurrences of nosocomial infection.⁵⁹

Management of Donor Animals

It is increasingly common to use animals owned by hospitals or veterinary personnel as donors for blood and ingesta (e.g., ruminal fluid) transfer to patients. Animals used for this purpose should be known to have a very low risk of contagious diseases, should be housed away from hospitalized patients, should be clinically healthy at the time of specimen recovery, and should be screened periodically for diseases that could be transmitted by use of transfer products. Diseases of concern that might be transferred by blood products from ruminants include bovine leukemia virus, bovine viral diarrhea virus and border disease virus, and anaplasmosis; similarly, horses should be screened for equine infectious anemia infection. Ingesta donors should be screened for Johne’s disease (Mycobacterium paratuberculosis avium) and S. enterica.