CHAPTER 66 Biosecurity
OVERVIEW AND VETERINARIAN’S ROLE
The importance of control measures for prevention of infectious diseases in individuals and populations has been realized for centuries, long before the modern microbiologic era. Throughout this chapter, we use the term “biosecurity” interchangeably with “infection control” to encompass all practices intended to prevent introduction and spread of infectious diseases within a group of equine patients and their human caregivers. Although used frequently by a variety of groups, the term biosecurity is not defined in any of the commonly used English dictionaries. Traditionally, biosecurity focused on prevention of the introduction of a disease agent into a population, whereas biocontainment focused on control of spread of the agent once introduced. Although this distinction is reasonably straightforward with relation to a unit such as a farm, a breeding station, or even a country, it is more difficult to separate “biosecurity” from “biocontainment” in the environment of an equine veterinary clinic, where disease agents are introduced and dealt with on a daily basis. Recently, the word “biosecurity” has been defined in a broader term as “work of strategy, efforts, and planning to protect human, animal, and environmental health against biological threats.”1
The need for infection control in human medical settings first became broadly recognized during the nineteenth century.2 Hospital-acquired or community-acquired infections have long been perceived as important problems for hospitals, day care centers, hospice or geriatric care centers, and similar institutions.3–5 In the United States, national surveillance for human hospital-associated infections using standardized methods was first implemented in 1970. Such surveillance provided a basis for development of control strategies, which ultimately resulted in improved quality of patient care, as measured by reduced infection rates, reduced morbidity and mortality, improved patient and hospital personnel safety, and reduced costs of hospitalization.6–8
Protecting the public health and promoting animal well-being are part of the veterinarians’ oath9 and have always been taken very seriously. Veterinarians have been recognized for their leadership role in control of zoonoses and food-borne diseases. However, concerns regarding nosocomial infections in veterinary hospitals have lagged behind those for human health care settings, despite veterinarians facing similar challenges associated with nosocomial infections in their patients, in addition to risk of zoonotic disease in caregivers and clients. As awareness increases among veterinary clinicians and their clients, infection control strategies at veterinary care facilities for horses and other animal species will develop in a manner similar to the advancement seen in human health care settings. A survey conducted in 2004 among equine veterinary hospitals indicated that all veterinary teaching hospitals in North America and many in other regions have implemented some type of infection control program, as have some of the more progressive private veterinary hospitals.2 As an indication of the rising prominence of this aspect of veterinary medicine, the Dorothy Russell Havermeyer Foundation sponsored a workshop dedicated solely to the topic of biosecurity and infection control in equine hospitals. This workshop resulted in the creation of the Veterinary Infection Control Society and publication of an issue of Veterinary Clinics of North America: Equine Practice dedicated to this topic10 (P.S. Morley, personal communication, 2005).
IMPORTANCE OF BIOSECURITY
Quality of Care and Liability
There is an inherent risk of nosocomial infection for any hospitalized patient, and therefore it is the hospital’s obligation to implement practices that will minimize those risks. According to a survey conducted among veterinary teaching hospitals in 1997, 12 of 18 responders reported 18 outbreaks of nosocomial disease between 1985 and 1996. Six of these outbreaks resulted in hospital closure, with conservative estimates of cost ranging from $10,000 to $550,000.11 These estimates did not include indirect costs related to loss of client-provider relationships, emotional stress inflicted on horse owners, loss of learning opportunity for students and residents, diminished morale of hospital staff and clinicians, and “bad” publicity. At the same time, even with well-developed infection control programs, it may not be possible to eliminate all nosocomial infections. Therefore, it is important to recognize that occasional nosocomial infections will occur even in hospitals that provide excellent quality care for their patients.
Nosocomial infections and iatrogenic injury (e.g., fractures) have been listed as one of the top 10 reasons for malpractice claims against human hospitals, and these cases were more likely to be adjudicated in favor of the patients than were all other types of cases.12 In the past, veterinary clients seemed to be more “forgiving” and willing to accept some risk of nosocomial infections as being normal. This attitude is changing, however, and it is increasingly likely that equine hospitals will face legal claims associated with nosocomial infection, and that these claims will inevitably lead to significant costs in both monetary and professional terms. It will therefore become increasingly necessary to develop comprehensive infection control plans to manage this risk.
Zoonotic Infections
Another important aspect of biosecurity is prevention of zoonotic infections. People working with animals have inherently increased risks of infection with zoonotic agents compared to the general public.13 Considering the wide variety of microbial agents that may infect horses, a relatively small number can be transmitted from horses to people, but these zoonotic infections may be devastating for affected individuals.14 This creates the potential for liability among veterinarians when people interact with animals in the hospital environment or because of the instructions or recommendations made by the veterinarians. This aspect of liability becomes particularly important as the percentage of the general public at increased risk, or those with some degree of immunocompromise, increases for a variety of reasons, including steroid treatment, cancer treatment, and chronic illness (e.g., infection with HIV or other agents); very young and elderly persons are also at increased risk.
Although the risks of acquiring a zoonotic infection from horses are generally low, a number of known and emerging pathogens can affect both horses and humans.15 In the United States the three agents most likely to pose a threat of zoonotic transmission (particularly to immunocompromised individuals) include Salmonella enterica, Rhodococcus equi, and methicillin-resistant Staphylococcus aureus (MRSA).14 R. equi was regarded as an equine-specific pathogen until recent reports of R. equi infections in immunocompromised people; contact with horses is not a clear risk factor for this infection in humans.16–18 Similarly, MRSA infection in horses and potential transmission between horses and people have been described only recently.19,20 Several equine viruses that cause encephalitis can affect both people and horses. Horses are usually “dead-end” hosts, with the exception of Venezuelan equine encephalitis, which can be transmitted from equids to humans.21 Although rabies is relatively infrequent among horses, it should be considered as one of the differential diagnoses in all cases of progressive neurologic disease.31,32 Reports have also described possible zoonotic transmission from a horse of Trichophyton equinum,22,23 Cryptosporidium parvum,24–26 Microsporum equinum,27 Streptococcus equi subsp. zooepidemicus,28 and Pasteurella caballi.29 In one study, isolation of Clostridium difficile from an equine hospital environment suggested that there was a potential risk of zoonotic infection.30
The emergence of Hendra virus in Australia dramatically demonstrates the importance of maintaining standard infection control precautions.33–35 One of the human patients who died from Hendra virus infection assisted in necropsies of affected horses without using barrier precautions, such as gloves, masks, and protective eyewear.14 This incident emphasizes the importance of maintaining high levels of infection control as standard practice, because it is likely that new infectious agents will be encountered in the future.
Similarly, pathogens of historical significance may reemerge as threats to human health. The extreme example of this is the emergence of biologic materials as potential bioterrorism agents, most of which are zooneses.36 The organism Burkholderia mallei, the equine pathogen that causes glanders, is listed as a select agent for potential as a biologic weapon.14 The ability to recognize animals with clinical signs consistent with diseases such as glanders and to stop spread of a bioterrorism agent among animals or between animals and humans may be very important in a potential outbreak situation.
Antimicrobial Resistance
Antimicrobial resistance is an emerging problem that affects our ability to treat individual patients (whether animals or humans), affects the control of disease in animal populations, and has significant public health implications. Antimicrobial resistance arises from interaction between bacteria and antimicrobial agents. Theoretically, all uses of antimicrobial drugs have the potential to promote the evolution of resistance in bacterial populations. Antimicrobial drugs provide a survival advantage for bacteria that are resistant to the drug used for treatment, which in turn promotes propagation of the genetic traits conferring this resistance. Drug resistance can develop stepwise by the accumulation of chromosomal mutations, or resistance genes can be transferred between bacteria from different taxonomic and ecologic groups by means of mobile genetic elements such as plasmids, transposons, or bacteriophages. Resistance genes acquired through these mobile elements are often linked together, so selection for resistance to one antimicrobial can promote resistance to a number of other antimicrobial drugs, with development of multidrug-resistant strains.37 In addition, genes rendering bacteria resistant to disinfectants (e.g., quaternary ammonium products) can be located on the same plasmid as antimicrobial drug resistance genes, therefore providing a survival advantage in the hospital environment to resistant bacteria.38
As noted in human hospitals, many of the nosocomial pathogens associated with equine hospitals also are multidrug resistant. This may be caused by high selection pressures applied through common use of antimicrobial drugs and disinfectants in hospital environments.20,39 In addition, many bacteria are very efficient at forming biofilms in the environment. These biofilms consist of an extracellular matrix that is produced by organized bacterial communities attached to a surface. Organization of bacteria in biofilms enhances their survival from a variety of environmental insults, including disinfectants and other antimicrobial treatments.40–47a Because bacteria in biofilms survive well in the environment, they may provide a continuous source of infectious pathogens that can cause nosocomial infections.
Several actions can be taken to minimize the impact of antimicrobial use. On one level, although antimicrobial drugs should be used when needed to aid the health of animals, they also should be used as conservatively as possible in accordance with published guidelines.48,49 Inevitably, however, bacteria will be exposed to antimicrobial drugs and disinfectants in hospitals, so patients will be exposed to resistant microorganisms in the hospital environment. Therefore it is essential that appropriate infection control precautions be used to help prevent spread of such agents from patient to patient and between patients and caregivers, as well as to help prevent resistant bacteria from establishing themselves in the environment.
METHODS FOR DESIGN OF AN EFFECTIVE BIOSECURITY PROGRAM
In designing a biosecurity program for an equine facility, it may be useful to apply a systematic approach, such as the Hazard Analysis and Critical Control Point (HACCP) system. The application of HACCP principles to biosecurity programs in veterinary hospitals and clinics has been described in detail.11 Most of the examples in this section address veterinary clinics. However, infection control programs must be tailored to each individual operation, and the same general principles guiding design of a hospital infection control program can be applied to any facility with a number of horses on the operation, whether an adjustment facility, a riding or boarding facility, or a breeding farm. Although the choice of rules governing infection control will vary between facilities, it is important that the rules are designed with all animals in mind, not only those suspected of having an infectious disease. For example, implementation of hand hygiene protocols and use of clean clothing and equipment should be encouraged as a part of basic standard care. Good biosecurity practices may prevent the spread of infectious agents from subclinical shedders of infectious agents that do not show overt clinical signs of disease.
Risks and Hazards
In addition, several diseases foreign to a given region should be considered in a control program. The most important diseases will vary with the geographic location of an equine establishment. For example, at the Colorado State University Veterinary Teaching Hospital (CSU-VTH), these include foot-and-mouth disease (FMD) and vesicular stomatitis (VS). As such, appropriate precautions are instituted during periodic outbreaks of VS in the region. Also, all visitors to CSU-VTH are asked to disclose recent foreign travel in an effort to exclude the possibility of FMD virus exposure.11
Control Points
The next step in designing a biosecurity protocol for an equine establishment is to identify the areas or processes where transmission of pathogens is likely to occur (control points) and implement measures aimed at minimizing the possibility of such transmission. Despite the existence of a large number of agents that pose a potential threat to the well-being of horses and their human care providers, there are some common features in the way these pathogens are spread and transmitted. The three main types of infection important from a biosecurity point of view are gastrointestinal (GI), respiratory, and surgical infections. Thus, efforts designed to minimize the spread of GI pathogens will likely be similar for all potential agents that have similar routes of transmission. Similarly, efforts designed to minimize nosocomial respiratory or surgical infections will likely be applicable to a variety of agents spread via these routes. The physical areas that should be targeted in a biosecurity program will vary between establishments, but usually these will include areas where the most susceptible animals (e.g., severely ill, immunocompromised, young, surgical patients) and animals most likely to be shedding contagious pathogens are housed (e.g., critical care or isolation units), away from high-traffic areas such as waiting rooms, examination rooms, and surgery. For an ambulatory practice, the focus should be prevention of spread of infectious agents from sick to healthy horses on a given equine facility and, as ambulatory practitioners, between facilities (see later discussion).
Preventive Measures
Hand Hygiene
Hand hygiene is a proven aid to preventing transmission of infectious agents.50 Personnel in contact with horses should maintain short fingernails to minimize accumulation of contaminants underneath fingernails and to facilitate effective hand hygiene. Hands should be washed before and after attending each individual animal. Gloves should be used in addition to, rather than instead of, good hand hygiene practices. Clean areas (e.g., doorknobs, drawer or cabinet handles or contents, equipment, medical records) should not be touched with soiled hands or gloves. Although handwashing is an effective way to control spread of infectious agents, frequent handwashing can also lead to skin damage and increased risks of colonization of hands with bacteria.51 Therefore it is important to provide not only soap and water to all employees of any equine establishment, but also lotions and moisturizers to promote frequent hand hygiene and maintenance of healthy skin.
In addition to soap and water, alcohol-based hand sanitizers can be a useful adjunct to handwashing in veterinary hospitals and can provide a practical option for improving hand hygiene for ambulatory clinicians (Fig. 66-1). Alcohol rubs are as effective as or more effective than handwashing in reducing bacterial contamination on hands when evaluated after study subjects performed physical examinations on horses.52 Alcohol can also be used in situations where fresh water is not easily available, such as at the stall side during a sporting event or in transit. Dispensers for hand-sanitizing solutions can be easily installed in any equine barn, and their frequent use should be encouraged to minimize potential spread of infectious agents. In particular, they should be used after handling any sick horses or quarantined horses. The cost associated with the use of alcohol hand rubs is less than that associated with products needed for handwashing.53
Barrier Nursing
Barrier nursing is another proven step in preventing the transmission of infectious agents54 (Fig. 66-2). In veterinary settings, this usually includes the use of disposable gowns, gloves, masks, and footbaths to prevent movement of organisms from one patient to another. This technique should be used in all isolation areas and for patients with special needs (e.g. foals, immunocompromised patients). Different practices have preferences as to how barrier nursing is accomplished. For example, opinions vary regarding the use of disposable plastic boots versus reusable rubber overboots. Similarly, opinions regarding efficacy of disinfectant footmats or footbaths vary among practitioners. In most situations, barrier precautions are effective if they are implemented in a knowledgeable way and all personnel understand the rationale behind their use. For example, disposable gloves will be ineffective as barrier precautions if the same pair is used on a number of animals. Gloves will serve their purpose only if they are used when working with one patient and then disposed of immediately when such contact is finished. Specifically, gloves that have been used to examine or treat a patient should be taken off before reaching for any supplies from a common shelf or drawer, before answering a phone, or before entering data on a computer.
Cleaning and Disinfection
Effective cleaning and disinfection are critical for breaking transmission cycles for contagious agents.55 With this in mind, it is critical that cleanable surfaces be maintained throughout any equine facility, particularly equine hospitals. Use of dirt floors or porous surfaces (e.g., untreated wood) should be avoided because these cannot be effectively disinfected. If porous surfaces are present, they can be rendered less porous by certain treatments, such as painting or sealing the surface.56,57 Care should be taken to ensure that proper dilutions of disinfectants are used and that the disinfectant used is effective against the pathogens in question. The latter becomes particularly important with difficult-to-kill pathogens such as parvovirus or rotavirus. Also, it is important to make sure that the product used is registered with the U.S. Environmental Protection Agency (EPA) and that all safety precautions recommended by the manufacturer are followed. All disinfectants should be stored in a safe place, particularly when access by children or domestic pets is a possibility.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
