Equine Events and Infectious Disease

A “perfect storm” of events can occur to cause a catastrophic disease outbreak that starts at an equine event, and often the local vets are the first called to action. Are you ready to respond? An equestrian event can act like a petri dish for a microbial population explosion. When horses travel from all over the country or from around the world to such events, they bring together the potential for other horses to be exposed to horses carrying disease agents.

Credit: Amy Dragoo

This might be done unbeknownst to caretakers, because in many cases, a horse might be incubating and/or shedding disease while not yet demonstrating clinical signs of illness. This makes the extent of spread that much worse because the not-yet-overtly sick horse is allowed to circulate among other competitors.

Compounding the potential of disease spread at an event are the visitors, veterinarians, farriers, pets and equipment (wheelbarrows, buckets, manure forks, bedding, bicycles, trailers, tack) that can carry infectious disease agents between infected and non-sick horses.

There often are no biosecurity practices in place at equestrian events, which means people, horses and equipment move unrestrained through the venue. The term “perfect storm” was applied to this scenario in the 2012 “Biosecurity Toolkit for Equine Events” published by the California Department of Food and Agriculture.

Another notable and complicating factor in the spread of equine disease at an event is related to the effects of transport stress, along with changes in routine and exercise demands—such modifications to a horse’s routine suppress its immune system, making him a target for microbial invasion. Trailer transport is known for its adverse effects on the respiratory tract; stress in general compromises the whole immune system.

An example of the devastating consequences of an infectious disease outbreak at an equine event was the Ogden, Utah, outbreak of EHV-1 neurologic herpesvirus (equine herpes myelitis, EHM) that occurred in May of 2011 at the National Cutting Horse Association show. A single horse that is shedding virus (or bacteria) is all it takes to start an epidemic.

Emphasis on Biosecurity

The emphasis on biosecurity at equine events has evolved considerably over the last two decades. At the Equine Diseases Forum in Denver, Colorado, in January 2016, it was reported that in 2005, the USDA’s National Animal Health Monitoring System (NAHMS) conducted a survey regarding equine health management strategies at national equine events in six states (California, Colorado, Florida, Kentucky, New York and Texas).

The overall results indicated that 32.7% required a health certificate, and 80% required a negative Coggins test for all horses at the event; 16.8% required vaccinations; and 29.1% provided an on-site veterinarian to monitor horses for illness.

A later study (2009) noted a big improvement in biosecurity practices: 75% required a health certificate, 100% required a Coggins test and 50% required a veterinarian on premises to monitor for disease. The 2011 EHM outbreak further highlighted the need for more consistent and overreaching biosecurity strategies throughout the equine industry.

The goal at all equestrian events is to minimize the risks of disease spread. Equine veterinarians can play an instrumental role in educating clients and event organizers on the best way to manage event venues to achieve this objective.

Equine Entry to the Site

Credit: Amy Dragoo

Colorado State Veterinarian Keith Roehr, DVM, spends a good portion of his time devoted to controlling disease for all species. He views certificates of veterinary inspection as an effective tool for minimizing the possibility of a horse bringing an infectious disease to a venue.

“This decade-long system is still the best method for veterinary inspection for interstate travel or entry to a venue,” he said. “Sometimes, event managers decrease the time the certificate of veterinary inspection (CVI) is done prior to their event. As an example, during a vesicular stomatitis (VS) outbreak, instead of 30 or 10 days, the CVI must be done within three days of the event.”

While not a perfect solution to eliminating disease entry onto a venue site, Roehr noted that a CVI is still the most cost effective means of surveillance. “It is important to right-size the timing of the CVI relative to the risk of infectious disease and the potential cost,” he said.

Roehr stressed that it is key to remember that the health certificate is just one tool, and that horse owners still need to be responsible and look at their horses carefully for any signs of an abnormality. “It is a good idea to monitor temperature at all events, although not all events mandate this procedure,” he noted. “As a veterinarian, you can recommend to your clients that twice-daily temperature checks are a prudent and precautionary strategy while they are traveling with their horses.”

Understanding the importance of performing twicedaily temperature checks enables your clients to be equipped with a thermometer prior to travel.

Roehr emphasized requiring horses to have influenza, rhinopneumonitis and rabies vaccines— as well as West Nile virus (WNV) vaccines—in advance of entry to the grounds.

“While equine herpes vaccine does not prevent the neurologic form, it may decrease the level of viremia in affected horses and thereby provide a bit of protection to other horses. As for WNV vaccine, while it is not a contagious risk, it is important to eliminate any disease possibility that confounds a neurologic diagnosis of equine herpes myelitis (EHM),” he said.

Immunizing against respiratory viruses once or twice annually is not only an excellent health management practice, but it also is required for many events associated with the United States Equestrian Federation (USEF) and the Federation Equestrian International (FEI).

“Vets helping with event management should develop a protocol,” advised Roehr. Some venues require hands-on inspection of every horse entering the site. “For an entry inspection to be practical, the event needs a veterinarian available who can make decisions to say that the sore in a horse’s mouth, for example, is due to a grass awn rather than a case of vesicular stomatitis that needs isolation.”

If mouths are to be inspected, Roehr recommended that veterinarians be provided with disposable gloves to discard between horses, or to have the owner lift the horse’s lips for inspection. This latter protocol prevents the vet from touching the horse and thereby enables a steady flow of participants going through the entry inspection.

Hand sanitizers are helpful to minimize passing contaminants between horses from the hands. The results of a study (Traub-Dargatz, et al., “AAEP Proceedings 2004”) noted that “the alcohol-based hand sanitizer and the chlorhexidine-alcohol lotion reduced the bacterial load on hands after a physical examination more than washing hands for 15 seconds with antibacterial soap containing 0.3% triclosan. As an alternative to hand washing, the alcohol-based hand sanitizers could be used if hand washing is not an option or if hands are not grossly soiled. These products are clearly labeled as not for use on grossly contaminated hands. If the practitioner had minimal visible contamination after examination of an equine patient, the alcohol-based products could be a feasible substitute for hand washing.” An appropriate amount (2-3 cm diameter) must be applied, rubbed in well, then allowed to dry for 15-20 seconds.

Roehr mentioned that transient outdoor events do not present as high a risk of an infectious disease outbreak because the horses aren’t stabled and are not as likely to share air or water, or to touch noses. By contrast, large and lengthy events maximize horse-to-horse exposure. At an event such as the National Western Stock Show, for example, horses are stabled in a common, closed building during the winter. Veterinarians do a walk-through twice a day looking for signs of infectious or contagious disease such as nasal discharge, cough, diarrhea or neurologic signs.

At every event venue, it is a good idea to provide handouts that contain contact information for personnel and the event veterinarian, including a 24/7 phone number. This enables rapid communications if a problem is identified.

Another important point to consider for event planners is to have a complete identification list of both people and horses on site so there is rapid traceability. As Roehr noted, “An outbreak like the EHM in Ogden, Utah, can cause a loss of millions of dollars. With that in mind, preplanning is important to know who the contestants are and how to reach them as quickly as possible.”

On-Site Biosecurity

In addition to monitoring the horses coming in as well as those already on site, biosecurity involves careful attention to detail at the venue. One way to help determine the specifics of biosecurity implementation at an event is to follow a horse around the event grounds to ascertain the possible contamination sites.

According to the Biosecurity Toolkit: “A complete biosecurity assessment evaluates stalls (number, size, construction, location), the availability of an isolation area (location, access, and suitability), feed and water areas (storage, sources, handling), communal wash stalls (number, construction and location), exercise areas (size, location, level of possible horse-to-horse contact), equipment (sanitation) and the parking area (location, separation and signage).”

As some examples, stalls that have doors opening to the outside of the building pose less risk of contamination than stalls with doors facing to the inside of a structure. Roehr stressed, “If there is shared air and/or nose rubbing at an event, then the horses may as well be in the same pen. One possible solution is to string plastic sheathing or a vinyl tarp between stalls as a barrier.” Ideally, there should be a solid wall separating horses.

Indoor air quality and the environment can impact virus transmission. In an outdoor environment, ultraviolet light aids in disinfection.

It is also important for there to be lines of separation where foot traffic stops. This might mean requiring foot baths for people permitted to go into and out of the barn area.

Frequent removal of stall bedding helps reduce ammonia and endotoxin contaminants of barn air, which are known to adversely affect equine airways. It is important that soiled bedding be disposed of away from foot traffic. “There have been lessons learned from previous outbreaks concerning this,” reported Roehr. “When VSV was a problem, some events didn’t manage manure, so flies were horrible. And they are vectors of disease.” Insect control, including fly sheets and sprays, can be helpful in limiting the disease spread.

 “Often what is required is a good dose of common sense,” noted Roehr. “Vets can look around and make simple suggestions that are not overly burdensome, but have excellent disease mitigation value.”

Not only can water sources transfer pathogens, but disposal of water from buckets also carries this risk. Hoses that have directly contacted water from which other horses have drunk are also potential fomites to transfer disease.

“If a horse is to be stalled at an event, it helps to drain automatic waterers and clean feed troughs to remove saliva, nasal secretions and feed,” Roehr pointed out. Handling of feed material is also critical in limiting disease spread. One example is to store feed in sealed containers to avoid access by rodents, opossums, birds and other animals. Feed should be stored away from moisture that promotes mold.

The biggest risk for disease transfer occurs from horses touching noses, sharing food and water, or having access to urine and manure. Similarly, disease can spread when a horse contacts surfaces such as fences, gates or stall walls that have been contaminated by another horse’s secretions containing infectious material.

Stall cleaning can be helpful to a point in reducing pathogen spread. Roehr noted that it is critical to remove as much organic matter (such as manure and leftover feed) as possible before putting a horse in a stall. Cleaning is the most important step, especially using detergents that break down organic material.

Once the bulk of the area is clean, disinfectant can be applied. There are disinfectants with varying toxicity to bacteria or viruses. Always follow the manufacturer’s recommendations. It is noteworthy that application of disinfectant to a porous surface or dirt gives minimal effect.

Pets can also carry disease. For example, a dog soaking itself in a stranglescontaminated water tank can carry disease around the premises on its wet body, especially if he jumps into another water tank. “Limiting or totally restricting dogs on site is an exercise in good common sense,” said Roehr. “Even if an area is scrubbed down, it is possible for dogs that are allowed to roam to bring infectious organisms from a contaminated area back to an area that has just been cleaned.”

People also can carry disease, said Roehr: “People may be on their hands and knees with a down horse—then, as they move about the property, they serve as significant vectors. Human hospitals have standard operating procedures to control transfer of infectious material.” The same biosecurity considerations should be applied to horse venues.

It is not always enough that horses have entry only with current certificates of veterinary inspection. In some cases, the transporting horse trailer can bring in disease. It is recommended that trailers be parked in areas that are not contiguous to the stabling and riding areas.

Suspicion of Disease

The objective of biosecurity is primarily to limit disease. But what happens when there is a disease outbreak?

The recommended chain of command for veterinarians to report suspicion of a sick horse can vary in different locations. Roehr urged that if you suspect there is something wrong, don’t wait for a positive diagnosis to report the suspicion. It might be necessary to report not just to the event personnel, but also to the state veterinarian.

An immediate response warrants moving a suspect horse to an isolation area. Signage and barriers around biosecure areas provide lines of separation. “A clean line is essential,” noted Roehr. “For example, in a dairy barn, the only thing that crosses this line is the tank hose for milk.”

Roehr said he has seen many mistakes made in the face of a reported outbreak:

• Although horses have been separated, tack and equipment was not. • Soiled coveralls were all hung together.

• People were allowed to move between isolation and other areas to feed and water without any supervision.

“Physical separation must be meaningful,” Roehr advised. “There should be a standard operating procedure on how one comes in and leaves an isolation area.” In addition, any non-essential personnel should not enter an isolation area. For example, farrier visits should be prohibited unless absolutely necessary.

Roehr stressed that veterinarians, farriers and adjunctive therapists all can serve as vector fomites, as can dogs and cats. He pointed out that vets as medical professionals are conscious of their visual appearance as perceived by clients.

It is possible that wearing coveralls and foot covers or rubber boots can scare a client, but the ramifications of disease spread should be considered in cases where precautions aren’t taken. “Every equine practitioner should have the ability and know-how to don and doff protective gear, as well as procedures to contain contaminated clothing,” stated Roehr. “Without these strategies, we have lost the essence of biosecurity.”

All personnel should have access to protective clothing at every event. While Tyvek clothing might be intimidating to horse owners, it could be necessary to use. Painter’s disposable coveralls available at local hardware stores can serve as temporary protective clothing. In addition, veterinarians need to properly dispose of medical waste.

“It is not possible to unendingly lock down a facility, so there must be the ability to move low-risk horses,” said Roehr. “State animal health officials can permit sick horses to return back home.” USDA VS 1-27 (Permit for Movement of Restricted Animals) provides for a sealed trailer to move horses that have had their temperatures taken for a specified period and are no longer febrile.


To maximize the dispersal of correct and up-to-date information, the Equine Disease Communication Center (EDCC, equinediseasecc.org) provides real-time information about diseases. Accurate communication minimizes the harm that can come from the rumor mill while also serving to educate veterinarians and the public.

Additionally, each state veterinarian’s website can be instrumental in advising people about the current status of a disease outbreak. Roehr reported, “Normally our website gets 5,000-6,000 hits per month, but when the Ogden EHM outbreak occurred, we received 70,000 hits in just two weeks. This communication resource provided an excellent opportunity for education of everyone.”

Take-Home Message

“Is there a point where biosecurity aspects compromise why people do what they do?” posed Roehr.

To educate event organizers on biosecurity practices, he suggested beginning the conversation between private practice vets and event organizers to “right-size” the tool kits for their facilities. “Veterinarians are in the position of being able to jumpstart the conversation,” he noted. This can serve as a means of customizing some biosecurity practices that might otherwise be overdone by event organizers.

However, the key point is that practical and effective biosecurity practices should be implemented every day, both on the farm and at an event, rather than waiting to implement practices following a disease outbreak.

“Our role and value as veterinarians— our expertise, knowledge and science—is more than just responding to a problem or crisis,” stressed Roehr. Indeed, communication and education are paramount to maximizing biosecurity for horses at home and away.


CDFA’s “Biosecurity Toolkit for Equine Events” is an excellent resource for vets, event managers and horse owners at: cdfa.ca.gov/ahfss/animal_health/pdfs/ Biosecurity_Toolkit_Full_Version.pdf.

AAEP offers “Biosecurity Guidelines” at: aaep.org/custdocs/BiosecurityGuidelinesFinal030113. pdf.

You can also refer to Colorado State University’s “Infection Control and Biosecurity Standard Operating Procedures” manual at: csu-cvmbs.colostate. edu/Documents/biosecurity-sop.pdf.


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