Chapter 30

Biosecurity on Horse Farms

Nathan Slovis

The equine community has always recognized veterinarians as a resource for knowledge about and prevention of infection. Horsemen recognize that veterinarians understand the pathophysiology of infectious disease and so also know about its prevention, control, and epidemiology. Veterinarians now have expanded roles in biosecurity and biocontainment, and the community seeks their expertise as leaders, educators, and mentors in outbreaks of infectious disease. The application of biosecurity and biocontainment protocols is important not only in veterinary facilities but also in equine breeding facilities, training facilities, and any place where horses may be housed in groups.

A biosecurity assessment should be approached like a physical examination. The basic objective is to identify deficiencies in the facility design, standard operating procedures, training of personnel, animal housing, and animal movement. It is pointless to visit a facility if the owner or employees are not dedicated to the evaluation and are simply going through the motions to comply with Occupational Safety and Health Administration requirements. It is important to talk to managers and personnel to understand how well the standard operating procedures are followed. By separately asking employees questions such as “What happens to aborted fetuses, animals with diarrhea, and new arrivals?” the consistency of their answers and the effectiveness of any training they have received can be determined. Before visiting a facility, the veterinarian should emphasize that no protocols or procedures should be on display before his or her arrival. The veterinarian should observe activities and take plenty of photographs, as well as take notes that will allow easy recall of findings once he or she has left the facility. Ideally, an assessment should be performed under “normal circumstances,” but most of the time, biosecurity assessments are requested because of an outbreak of disease.

Prevention of Transmission of the Infectious Agent

Prevention is one of the most important elements in any biosecurity plan. Transmission of infectious agents requires a source (or reservoir) of the infectious agent, a susceptible host with a portal of entry receptive to the agent, and a mode of transmission for the agent. Identification of areas where or activities by which transmission of pathogens is likely to occur offers the opportunity for implementation of measures aimed at minimizing the possibility of such transmission. During the assessment and development of prevention and control activities targeted against infectious diseases, the weakest link in the chain of infection (agent–transmission–host) must be considered for each pathogen. If possible, all of this must be accomplished while allowing for reasonable flow and function within the animal facility.

Infected animals and those with a history or clinical signs suggestive of contagious infectious disease must be prevented from having direct contact with the remainder of the animals at the facility. Strategies aimed at interruption of transmission should be tailored to the type of transmission involved. For instance, airborne transmission can be prevented by isolating the horse at premises where uninfected animals are not currently housed or in a facility that has no shared airspace with such animals. The biology of diseases, such as vesicular stomatitis, that are transmitted by vectors can be interrupted by destroying the vector and by use of repellents. Rodents also serve as vectors for infectious disease and should be routinely trapped and removed from the premises. It is important to keep traps freshly baited.

In many instances, disease is best prevented by modification of the host, such as by developing or boosting immunity through active immunization. However, because few, if any, vaccines protect all animals from disease, a comprehensive control strategy should start with vaccination but also include other control activities targeted at the host, such as use of antimicrobials for chemoprophylaxis and improving the nutritional status of neglected animals, which may be more susceptible to contracting the disease.

The feasibility of a containment policy should also be assessed. This depends not only on sociodemographic factors but also on the operating needs of the facility, cost, and availability of resources. Implementing and maintaining even a basic biosecurity program requires trained personnel and an adequately staffed facility with appropriate supervision. Outbreak investigations have indicated an association between infections and understaffing, and this association has consistently been linked with poor adherence to hand hygiene. Old barns with cracked wooden surfaces can be very difficult to clean (Figure 30-1). Sealing the walls with polyurethane can help, but the procedure must be repeated on a scheduled, recurring basis. Some facilities may not be able to afford the ideal situation of a dedicated lead rope and halter for every horse. Operations that routinely buy and sell horses may accept the risk for outbreaks of contagious disease, such as Streptococcus equi infection, as the norm and choose not to impose a quarantine protocol and isolate newly arrived horses.

Figure 30-1 Photograph of an older barn with wooden walls that have cracked surfaces and flooring that needs resurfacing. Such structures can be challenging to disinfect effectively.

A surveillance component to the infection control program is essential to gauge the effectiveness of the biosecurity policies. Data collected during the surveillance process will provide information about current protocols but also provide early warning about potential contagious disease threats. The type of surveillance program is determined by factors such as cost, efficiency, and the number of high-risk cases routinely housed in the facility.

Surveillance Programs

Active surveillance is easily employed and can take several forms, the most common being collection of a sample or samples (nasal swabs or feces) from sick horses at the farm for the express purpose of detecting an agent or agents of concern. Because it is not reasonable to collect samples from every horse in the hope of detecting every possible infectious agent, effective active surveillance in a farm setting targets the high-risk population and determines which agent or agents are of greatest concern. For example, horses recently discharged from a hospital may shed Salmonella spp, which can lead to outbreaks of salmonellosis. Therefore, if a large farm sends numerous horses to a clinic for orthopedic corrections or embryo transfer, fecal culture of these horses at the time of discharge may be of benefit to your client’s farm. This would allow additional precautions to be taken with horses known to be shedding Salmonella as well as rapidly detecting nosocomial transmission of Salmonella.

Environmental surveillance is another detection method that can easily be implemented at the farm. It involves collection of environmental samples for culture of organisms known to remain viable in soil, dust, or water. At farms that are having problems with Clostridium difficile, for example, environmental sampling with an electrostatic cloth ¹ wiped over surfaces of the stall, equipment, and treatment rooms may be performed with real-time polymerase chain reaction testing.

The Infection Control Plan

Before writing an infection control plan, a staff member at the farm should be designated as the head of infection control. This individual works closely with the veterinarian and is responsible for implementing the infection control program (written by the veterinarian), updating the protocols on at least an annual basis, handling incident reporting, collecting and disseminating data, keeping records, and monitoring compliance. As outlined by the National Association of Public Health Veterinarian’s Compendium of Veterinary Standard Precautions, an effective infection control plan should meet certain criteria. It should reflect the principles of infection control previously mentioned, be specific to the facility and practice type, be flexible so that new issues can be addressed easily and new knowledge incorporated, provide explicit and well-organized guidance, clearly describe the infection control responsibilities of all staff members, and include a process for the evaluation of infection control practices. The plan should also provide contact information, resources, references, a specifically reportable disease list, public health contacts, local rabies codes and environmental health regulations, Occupational Safety and Health Administration requirements, websites, and client education materials.

An essential component of infection control is the need for continual updating of the documented policies. Emerging and reemerging diseases, such as influenza and antibiotic-resistant bacteria, require that the infection control policies be updated on at least an annual basis to take into account new information about transmission, prevention, and control of those agents. The infection control procedures should also include specific instructions for data collection of those agents relevant to the facility type, such as antimicrobial resistance, zoonotic diseases, or nosocomial infections.

Education, Training, and Enforcement

Without staff education, training, and enforcement, a written infection control policy will not be effective. Education and training help ensure consistency in use of the procedures and also allow for a thorough review process of all policies decided on. In addition, documented policies demonstrate due diligence on the part of the practice and can be useful from a legal liability standpoint in cases of nosocomial or zoonotic infection.