Handling disease outbreaks at equine events (Proceedings)


Maintenance of excellent health and biosecurity standards at the level of the farm is the MOST effective way of maintaining an outbreak-free industry. All disease outbreaks have an index case and all index cases have a point of origin. Because horses are usually maintained at a 'home" farm, then the origin of any outbreak should be traced back to the farm level.

Maintenance of excellent health and biosecurity standards at the level of the farm is the MOST effective way of maintaining an outbreak-free industry. All disease outbreaks have an index case and all index cases have a point of origin. Because horses are usually maintained at a 'home" farm, then the origin of any outbreak should be traced back to the farm level.

Management and ownership of ANY farm can control disease outbreak and minimize risk to the industry. Control of disease at the farm level is through 1) exit and entry, 2) population management, 3) proper disinfection and 4) preventative health practices,. The focus of this discussion will be the first three. Finally if an outbreak occurs, the steps are outlined for outbreak control.

Table 1. Concepts of healthy transport


Transport of sick horses onto a farm pose the single biggest risk for introduction of new diseases. Maintaining and adhering to strict transport protocols is essential. Clients need to be educated that this is completely in their control. What comes through the gate becomes their problem (and expense), what stays on the other side of the gate is someone else's problem. Farm owners should have three simple expectations of transport into their farm: 1) cleanliness, 2) horses are free from disease, 3) accurate identification and health information is provided on every animal on transport. Seems simple but given the plethora of people hauling their own and other horses all over the continent and throughout the world, not all will maintain appropriate standards. Thus it is imperative that veterinary health professionals education their clients on this important element of horse health. Finally, healthy transport is a welfare issue; horses undergo stress, are food and water deprived, and are exposed to noxious substances in terms of air quality and infectious disease during transport. Minimization of these elements ultimately is essential to the care and well being of animals.

Population Management

Age and Reproductive Status Management. On multi-use farms, most biosecurity is aimed at protecting the mares and foals from infectious agents. This is important, but the healthy performance population really needs to be protect from the mares and foals! Epidemiologically fecal

pathogens are MORE associated with young animals and, although not adequately, researched, the post-foaling and lactating is likely to be shedding organisms with which she is chronically infected or habitually exposed. In addition, the older horse may be prone to subclinical infections of many bacterial pathogens such as

Transport Status: Horses are not going to a dog park to play when they come to a new location. They do not need to romp around and get to know all the other horses. They do not need to be socialized. All horses that are shipped on and off farms should be maintained away from the resident farm population for a MININUM of 10 days and preferably 3 weeks. All temporarily stalled animals (such as for breeding) should NEVER have contact with the resident population.

Disease Status: For any sick horse, traffic, quarantine, and barrier precautions need to be immediately instituted. Not all farms have quarantine facilities and most do not! However, management can greatly reduce spread of disease and an outbreak.

Outbreak Control Once Disease Occurs

Veterinarians are the first line of defense against infectious disease outbreaks. Current problem and case based equine medicine likely does not prepare new graduates in outbreak control. Control of an infectious disease is based on correct application of the principles of population biology and transmission dynamics of a particular infectious organism, basic microbiology, and basic epidemiology. Overall, training in diagnostic medicine is declining due to loss of state and federal support in our programs and reprioritization of veterinary student training that primarily track into clinical programs. Unfortunately, this does not lighten the responsibility of the primary care veterinarian in control of infectious diseases and in the liability associated with failure to avert economic disaster or animal loss.

The goal for this step in the biosecurity process is that once a disease has been identified, horse movement stopped and biocontainment perimeters defined, what happens next? Four basic tasks must be fulfilled 1) communication of possible risk within and outside of containment, 2) isolation and quarantine of potentially infectious horses, 3) trace-back to other horses that may potentially spread the disease, and 4) safe release of horses with resumption of normal activities.

Communication Communication to the farm personnel regarding potential for disease to hinder their program if it is not adequately handled at the point of identification of sick animals is paramount. The information should contain the agent identified, a case criteria for risk assessment, identification of horses at most risk for exposure, and daily updates on status. Communication must be done to gain trust of both the public and the industry. This requires accountability, involvement of all owners if multiple and their veterinarians, and transparency. Information must be provided early. Communication must also contain information regarding realistic risk for their horses and preventative strategies for horse owners.

Isolation and Containment

After the identification of a specific agent is made, then these isolation and containment practices should be refined to be agent specific. Isolation is not a ward that allows nose to nose contact or contract with body secretions. This means all personnel must dress in personal protective gear between isolated horses, stall tools are kept separate, and stalls are completely decontaminated between animals. Containment practices should minimize traffic to these stalls (work with non infected population, then infected populations) with control points established where there is hand washing and foot baths after personal protection equipment is removed. In addition these control points should be thoroughly decontaminated daily or even twice daily. Most research indicates that failure to isolate is one of the most important factors that facilitate spread of disease within groups of individuals.

Trace Back

If this disease results in closure of a premise, most of regulatory personnel's time is taken up with trace back. This is the process of finding all horses that may be exposed to the index case outside of the primary barrier. The sooner and more complete this task, the better protection for the industry. Unfortunately this is very difficult. The problems associated with this are 1) poor record keeping and 2) lack of effort on the part of all associated personnel to create all possible connections early in the process. The most common lack of early association is in shipping or animals that have been in contact but are now unaccounted for. All point-to-point contacts must be recorded by everyone. This includes horse-to-person and horse-to-building, horse-to-equipment points of contact. Most of the initial failures to identify all contacts are usually inadvertent omissions, however, in many industry situations there are those that will purposely omit points of contact. Only by communication with all parties involved will all the points be identified early. Again, most disease modeling predicts that failure to successfully trace back all infected persons (or animals) is one of the most important factors that facilitate spread of disease to many locales.

Release from Containment with Disease Specific Plans

Finally, there must be implement disease specific guidelines for maintenance and release of horses from quarantine. If a horse meets a case criteria, a specific testing protocol should be implemented and followed. Continuous changes to this protocol are costly for the owner and usually prolong quarantine unnecessarily. The time for quarantine for all specific diseases should be strictly followed.

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