How Much Is Enough? How Much Is Too Little?

Exposures to contagious disease threats, HAIs in patients, and zoonotic infections in care providers are undeniable risks in every veterinary practice. Because veterinarians have ethical and legal obligations to take reasonable protective actions to prevent their patients and employees from foreseeable harm associated with their actions (and inactions), it is clearly possible to not pay sufficient attention to infection control efforts.

■ BOX 46.1

Principal Goals and Major Action Areas for Infection Control Programs in

Veterinary Medicine

Although HAIs are an undeniable hazard associated with caring for patients, and although it is possible to reduce the risk of infections through a variety of prevention strategies, it is important to note that not all HAIs are preventable using practical and cost-effective control programs. Even impractical and cost-prohibitive programs would not eliminate HAIs, since an undefined but undeniably significant “nonpreventable” fraction of infections will occur despite any infection control practices. To be most successful, it is important that over time administrators and personnel responsible for infection control programs strive to better understand and target prevention efforts at the preventable fraction of all HAIs.

Principles of Infection Control

In general, all comprehensive infection control programs center on the four principal goals and five major actions listed in Box 46.1, but each operation must tailor programs to opti­mally fit their specific practice. When initiating an infection control plan, it is important to make a global assessment of the contagious disease hazards in a practice, the level of risk aversion, and the resources that can be expended on infection control efforts. If a veterinary practice predominantly works in preventive health care under extensive field conditions, the contagious disease hazards may be less common and less severe than those encountered by a practice that concentrates on intensive care of patients in a hospital.

While considering this assessment of mindset and resources, the next step in developing an infection control program is to elaborate the specific goals for the program. Managers can then tailor their infection control program to meet their specific practice needs using a systematic process for evaluation of disease hazards and design of control systems. This systematic approach allows design of control systems that triage efforts to optimize efficiency.

Each infectious disease may be considered individually in this evaluation process, but it is useful to remember that control measures that are effective against one agent are usually effective against others, particularly if they share common routes of transmission or have common risk factors in patients. Design of infection control programs should focus on practical actions for known problems, but it is important not to ignore the potential for newly recognized and re-emerging diseases.^26-28 The general strategy used in infection control protocols should be sufficiently rigorous to protect against most emerging issues, at least at a basic level.

Another critical aspect in the practice of infection control is effective targeting of efforts. Taken to hypothetical extreme, the most rigorous infection control methods would prescribe that every patient be handled in complete isolation using barrier precautions verging on those used by “hazmat” personnel. Clearly this is not practical or needed in most situations, yet in a few rare circumstances this level of precaution is warranted. In many more situations, some lesser level of precaution is warranted beyond that used in casual encounters with animals in their home environments. By their very nature, these extra control measures will inevitably inconvenience caregivers and clients in addition to increasing costs associated with care. These measures could also affect the quality of patient care and result in a corresponding increase in morbidity when taken to the extreme. The challenge is to target prevention efforts to just those patients that warrant increased concern and to use the most appropriate, albeit inconvenient, methods for controlling risks to personnel and other patients.

Another side effect of the inconvenience created by infection control efforts is that people by their very nature gravitate to the most convenient methods for daily activities. As such, the more personnel are inconvenienced through infection control efforts, the less likely they are to follow prescribed policies unless they understand and believe that procedures are needed and have value. Thus a critical component of any effective infection control program is maximizing awareness of personnel and educating them on potential hazards and the value of established control measures. Establishing interactive communication regarding risks and concerns coupled with logical, objective, evidence-based presentations is clearly an important approach for convincing personnel of the need to fully participate in infection control efforts.

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 receive adequate information prior to treatment to allow them to appropriately weigh risks and benefits when making decisions for their animals and themselves.^29,30 As professionals with specialized training, veterinarians can be assumed to have knowledge about the health and care of animals that goes beyond that of people without this training. An agreed-upon component of the informed consent process is the disclosure to owners of potential risks that may be associated with a veterinarian’s management of animals, particularly in situations in which there is greater than average risk for a particular adverse consequence.³¹ As such, it is reasonable and prudent for veterinarians to routinely disclose the potential for HAIs as part of the informed consent process for all patients. This is especially true for patients with an enhanced risk of acquiring HAIs (e.g., because of required invasive procedures or because patients are compromised), but can also be applied to risks for all patients. For example, if there is a known or suspected increased risk of nosocomial infections for patients at a facility, there is likely an ethical and legal obligation to disclose prior to admission how this risk pertains to new patients. It is extremely prudent to document the informed consent process in writing with clients. Sometimes there is reluctance to do so based on concerns that it may deter clients from using a facility, but this process can also provide an opportunity to educate clientele (and thereby increase their overall understanding) and highlight measures that are being used to mitigate risks.

Paying for Infection Control Activities

As mentioned previously, procedures used to decrease risks of HAIs inherently increase labor and material costs related to patient care. Infection control activities are an essential part of delivering veterinary care, and it is reasonable to pass on these costs to clients. It should not be expected that these costs reduce profits or be paid by veterinarians or hospitals. Remembering that only a portion of HAIs are preventable, if veterinarians have met an expected standard of care for infection control, it is reasonable to assume that costs incurred for treating complications associated with HAIs are paid by the client. Knowing that HAIs are an expected risk, veterinarians and hospitals should develop financial plans to address these risks. Consider how expenses for infection control efforts will be assessed and tracked, as well as how a practice might recover these costs from clients. The costs could be passed on to clients by directly accounting for each item, which is most reasonable when specific charges can be attributed to a specific patient (e.g., increased nursing or materials costs associated with care of a specific patient in isolation). However, this is less applicable when costs relate to care and protection of more than one patient (e.g., costs related to cleaning and disinfecting the hospital environment). In these situations, 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 surcharge) or to include these costs in overhead that is compensated by general admission or hospitalization fees. It is also wise to have a contingency fund that will allow veterinarians to address special circumstances, such as when it is necessary to investigate or mitigate against suspected outbreaks of infections.

Environmental Hygiene and organic debris, and may survive for very long periods. Even with relatively inhospitable conditions, many organisms persist for extended periods. If environmental pathogens can contact the appropriate body site of a susceptible individual in adequate numbers, disease could result. Environments where patients are housed or veterinary care is delivered can be expected to have greater numbers of environmental microorganisms than corresponding areas with less animal and human traffic.³²

The relevance of environmental contamination is often difficult to determine. Even recovery of genetically indistin­guishable organisms from the environment and from a patient does not confirm that exposure to an environmental reservoir was the source of infection, since it can be difficult to distinguish cause versus effect. However, environmental contamination is of concern for both direct (e.g., oral inoculation from a reservoir of microorganisms in a stall) and indirect (e.g., transmission of an organism from an environmental reservoir to the hands of a care provider and then to an animal) transmission. Measures should be used in all veterinary care environments to reduce the environmental pathogen load. This involves cleaning and disinfecting environmental sites.

Cleaning

Cleaning is defined as the removal of all visible debris³³ and is arguably the most important step in decontaminating 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 the efficacy of the disinfection process by providing optimal conditions for desired biochemical reactions, but it 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 removal of all bedding and feces and scrubbing surfaces to remove adherent debris and biofilms. Detergents should be used to loosen organic debris, emulsify oils and fats, and remove biofilm. 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 stalls and other large areas, less labor-intensive methods are often sought. For example, high-pressure (>120 psi) washers are frequently used in barns and hospitals. There are theoretical advantages that seemingly justify use of high-pressure washers, especially when they are designed to dispense high-temperature water and steam. Although power washing can be quite helpful in removing organic debris, this process can also exacerbate infection control problems by aerosolizing and widely dispersing infectious agents. Further, when used indiscriminately, they can damage surfaces, which then impairs subsequent cleaning and facilitates survival of pathogens. 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 unwanted consequences. Using high-pressure systems on surfaces with large amounts of gross contamination should be avoided.³⁴ In areas likely to be contaminated with important contagious pathogens (e.g., isolation facilities), it is logical to use high-pressure systems minimally or at least only as a secondary cleaning process on surfaces that have already been manually cleaned and disinfected.

Disinfection

Disinfection is the process of substantially reducing the burden of microbial contaminants on inanimate objects in order to reduce the likelihood of transmission of infectious agents. This should be contrasted with sterilization, which is the inactivation of all microbial agents on an object, typically performed only on materials used in invasive procedures. Disinfectants are biocidal chemicals that must be used at appropriate concen­trations, allowing for adequate contact time to achieve the intended effect. Even with proper cleaning and selection of an appropriate disinfectant, disinfection errors can occur. It is also important to remember 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 with surface disinfectants.³⁵

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 prior to 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 method to easily 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 a variety of vendors 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 personnel 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 to provide maximal microbial reduction. Chemical reactions that produce dis­infection are slowed in cold temperatures, which should be considered when determining the amount of contact time required. Disinfectants should never be combined because of the potential for inactivation and production of noxious or toxic gases.

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 between 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 that can be used in all situations in large animal facilities, although oxidizing agents such as accelerated hydrogen peroxide and potassium 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 alternative products should situations that require a higher level of activity be encountered. There is no evidence that rotation of disinfectants is useful.

■ TABLE 46.1

Disinfectants Commonly Used in Veterinary Medicine^a

^aIt is critical to handle disinfectants and other chemicals using appropriate safety precautions. Refer to the Material Safety Data Sheet (MSDS) for each product to obtain recommendations on appropriate handling and recommended personal protective equipment.

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, certain pro­cedures can be performed to facilitate disinfection.³⁴ 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 result 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, since 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 HAIs.¹ If obtaining a seamless, water- impervious floor surface is not possible, floor coverings should be completely removable (i.e., rubber mats over sealed concrete floor) and must be removed regularly for disinfection. 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, this material should be completely removed and discarded between every patient.

Animal Contact Items

For items that are used in patient care, disinfection processes are sometimes divided into three categories: high, intermediate, and low level. High-level disinfection involves eliminating all viruses and vegetative bacteria but is not expected to inactivate bacterial spores, fungal spores, or protozoal oocysts. High- level disinfection is difficult to attain and uncommonly used. Intermediate-level 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 and enveloped viruses. Items requiring disinfection should be classified according to the level of disinfection required; Table 46.2 shows examples of these.

After use, all items in a patient's stall should be considered to be potentially contaminated with pathogens that the animal might be shedding. Thus 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 disinfecting surfaces that patients contact orally, such as feeders and water bowls, as well as surfaces likely to be contacted by hands of personnel. Appropriate decontamination of water bowls can be problematic. Ideally, the water supply should be turned off, and the bowl should be drained, cleaned, and applied with disinfectant for an appropriate time before it is rinsed and the water is turned on again. Nets used to hold hay have

■ TABLE 46.2

Examples of Items Requiring Different Levels of Disinfection

a high likelihood of contamination and are difficult to disinfect without use of gas or plasma sterilization techniques. As such, 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.³⁶

Twitches and muzzles have a high potential for contamination with pathogens such as Streptococcus equi and 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, is 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 the ability 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 used on animals that are known to harbor or are likely harboring nasal or upper respiratory tract pathogens should be considered contaminated and the material discarded or disinfected.

Few areas show a greater difference in approach to infec­tion control between human and veterinary medicine than the handling of hypodermic needles after use. In human medicine, recapping needles is strictly forbidden because of the potential for needlestick injuries and subsequent exposure to life-threatening bloodborne pathogens. In veterinary medicine, recapping needles is very common, and needlestick injuries are often not perceived to be a significant health threat to veterinary personnel. Currently, there are minimal risks to veterinary personnel in almost all situations regarding blood­borne transmission of infectious agents from large animals. However, infectious disease hazards clearly continue to emerge, and it is prudent to develop safe practices that minimize the potential for exposure to bloodborne pathogens that might be transmitted from domestic large animals. In addition, physical trauma from the needle and accidental inoculation of some vaccines (e.g., RB51 modified-live Brucella abortus vaccine),

■ BOX 46.2

■ BOX 46.3

Indications for Hand Hygiene in Medical Practice

• When hands are visibly dirty or contaminated with protein­aceous material, blood, or other body fluids.

• Before direct contact with patients.

• Before donning sterile gloves for invasive procedures (e.g., suturing wounds).

• Before inserting an indwelling urinary catheter, peripheral vascular catheter, or other invasive device that does not require a surgical procedure.

• After contact with a patient's intact skin.

• After contact with body fluids or excretions, mucous mem­branes, nonintact skin, and wound dressings.

• After contact with an inanimate object in the immediate vicinity of a patient.

• After removing gloves.

• Before eating and after using a restroom.

Adapted from Centers for Disease Control and Prevention: Guideline for hand hygiene in health-care settings: recommendations of the Healthcare Infection Control Practices Advisory Committee and the HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force. MMWR 51(No. RR-16), 2002. http://www.cdc. gov/mmwr/PDF/rr/rr5116.pdf. (Accessed August 14, 2018.)

medications (e.g., hormones, cancer chemotherapeutic drugs), or the person’s own skin microbiota can lead to serious outcomes.