by Marilyn Munzert
As you prepare for competitions and events, keep in mind that taking your horse off your property puts him in close proximity to strange horses. At an event, disease can be transmitted through the handling of many horses by judges, trainers, veterinarians and farriers, or by people petting multiple horses. Horses walked around the grounds may be inclined to sample piles of leftover hay, burying their muzzles in places where other horse noses have been.
Direct or indirect contact with body secretions passes infective micro-organisms. Sources include secretion from nasal passages, pus, blood, feces or urine. Indirect contact occurs when equipment or people pass infective secretions to a vulnerable horse.
Micro-organisms such as viruses, bacteria, fungi and parasites have not only evolved efficient mechanisms to infect a host horse, but they also induce symptoms that amplify disease spread: Coughing, sneezing and nasal discharges pass respiratory infections such as the influenza virus, equine herpes (rhinopneumonitis) and strangles between horses. Bites from mosquitoes transmit equine encephalomyelitis or West Nile virus from infected birds. Large biting flies can transmit the equine infectious anemia (EIA) virus between horses. Other common transmissible diseases and health problems include vesicular stomatitis virus, rabies, diarrhea-causing micro-organisms, and skin infections such as ringworm or lice.
Stress, a known risk factor for increasing a horse’s susceptibility to infection, is a regular component of a competition horse’s life. Transport, altered routines, feed changes and the physical demands of athletic sports are stressful influences. A horse in a trailer, with his head tied in an elevated position for longer than six hours is more susceptible to infection: Studies have shown that bacteria in the back of the throat increase be 20 percent. Airway clearance mechanisms on a cellular level rely on adequate tissue hydration. Along with other stressor involved in transport and competition, dehydration may play a significant role in the development of respiratory diseases.
Typical incubation periods for infectious diseases range from days to weeks, during which time a horse can transmit disease to other horses even if he is not yet showing signs. A horse seemingly recovered from an infection, like strangles, may remain contagious for weeks or months; although the infected horse doesn’t appear sick, bacteria continue to shed from his guttural pouches to contaminate shared drinking water or infect others via direct contact with his nasal secretions.
To limit disease spread by horses that travel off the farm to events with strange horses, isolate a traveling horse from resident horses for two to three weeks following the horse’s return. Ideally, the horses that travel to and from local, regional, or national events are housed in one barn while the resident horses that don’t travel are housed in a different barn and/or paddocks. It may be difficult to accomplish, but these are proven biosecurity strategies.
An important part of your preventive disease-control program relies on spring immunizations, including those that target mosquito-borne viruses (encephalomyelitis and West Nile virus) and contagious respiratory viruses (influenza, rhinopneumonitis/EV-HV-1 or strangles). Annual immunizations also protect against tetanus and include the rabies vaccine in endemic areas. Viral respiratory vaccines are boosted again in the fall to carry a horse through the winter.
To maximize disease resistance, it is best to administer vaccines two to three weeks in advance of anticipated exposure. To maintain the general health of individual horses as well as herd health, every horse should also be up-to-date on parasite control as determined by annual fecal egg counts.
Certain steps are instrumental in minimizing disease outbreaks when a new horse is introduced to a property, or at events where horses come from many geographic locations.
Every horse should have a current negative Coggins test for EIA, and should receive a health exam and certificate of veterinary inspection three to 10 days prior to going anywhere. Further diagnostic testing can be performed on a horse with a questionable medical background or one that comes from a farm with a recent history of disease exposure.
To minimize disease transmission, avoid nose-to-nose contact between horses. When introducing a new horse or attending a show, don’t share hay or feed between horses, especially if fed in buckets. Instead, supply each horse with personal feed and water buckets. Don’t permit your horse to drink from common water tanks or buckets, and avoid filling small buckets from large tanks contaminated by other horses, or using a hose that has been dunked into a common-use tank. Also, refrain from dunking sponges, bits or your hands into communal water tanks. Use a separate bucket of water specifically for those purposes and discard fouled water.
Similarly, you shouldn’t share tack, equipment, grooming tools or blankets with other horses. However, if equipment is shared, thoroughly clean and disinfect it before using it on other horses. Resist the urge to pet anyone else’s horses. Wash your hands thoroughly before and after handling horses when possible to remove organic debris, then use antiseptic gel after washing so it can have the best skin contact for disinfection.
At home, hygiene and biosecurity practices are critical to defending against the spread of infectious diseases. An isolation area keeps newcomers separate from resident horses, provided the horses are housed a sufficient distance apart; a shared fence-line doesn’t provide an adequate barrier between a new horse and the general population. Maintain this separation for two to three weeks. Distinguish isolation boundaries with signs and limit access only to necessary personnel. Clearly communicate biosecurity measures to everyone on the farm, including boarders, visiting veterinarians, farriers and feed suppliers.
Carefully monitor your horse for signs of disease at an event, when returning after commingling with outside horses, or if he in isolation. Do this by checking rectal temperatures morning and night, monitoring appetite and feed intake, manure and urine output, and general well-being. Record this data in a daily log. Inspect for signs of disease, such as cough, nasal discharge, loose feces or fever, and immediately consult your veterinarian about any abnormalities. Quarantine a suspect horse away from all other horses. Anyone who comes into contact with a sick horse should follow hygienic practices before interacting with other horses on-site.
Another issue to address is the removal of rodent and vermin attractants. These creatures serve as disease vectors by carrying bacteria and parasites on their bodies. Discourage their presence with rodent-proof storage containers made of metal or heavy plastic, secured with lids. Lock feed-storage containers to prevent access by opossums that could contaminate them with their feces and transmit equine protozoal myelitis (EPM). Sweep daily to remove debris and spillage, and secure garbage and discard it regularly; these materials are attractive as food and for nesting. Clean and eliminate areas that create hidden nesting sites for small animals.
The smallest management details often have the greatest impact on a horse’s well-being. A comprehensive anti-disease program along with biosecurity measures provide the healthiest environment for your horse. Scientific findings are always evolving and modifying methods of providing health care. With that in mind, consult regularly with your veterinarian to achieve the best results from preventive health care strategies.
Specific measures to defend against infectious equine diseases
by Marilyn Munzert