March 2022 Issue

EAST COAST EQUESTRIAN March 2022 Page 57 By Jackie Bellamy-Zions, Equine Guelph “Most horses have been ex- posed to the equine herpes virus,” says Dr. Diego Gomez-Nieto, researcher at the Ontario Veterinary College. Gomez has been part of a research study on the Equine Herpes Virus which discovered the nasal microbiota of infected horses differed significantly to those of a healthy control group. The study came together quickly and was con- ducted on a horse farm in Ontario that was experiencing an outbreak. The research paper explains that the nasal bacterial microbiota of healthy horses is richer and more diverse than that previous- ly reported using culture-based methodology. “We found that there is a myriad of different types of bacteria in the nasal cavity of the horse, and they are kept in a normal balance,” says Gomez. “However, when there is a respi- ratory infection from a virus (like equine herpes virus), the normal balance of the nasal bacterial population is disrupted, allowing some pathogenic bacteria to pro- liferate and cause disease. One of those diseases is pneumonia. The results of our study help to explain why and how pneumonia develops in horses after a viral infection of the respiratory tract.” For most horses, EHV does not cause any serious problems. Signs of illness may include fever, limb edema, and nasal dis- charge. When a horse is shedding the virus, it is highly contagious and quarantine protocols are of paramount importance. “If horse owners and care- takers detect any of those clinical signs, they should consult with their veterinarians and pursue testing,” says Gomez. “Sometimes the only sign will be fever. The result of our study and other studies shows that if a farm is experiencing an outbreak of equine herpes virus, owners should check temperatures for all horses twice a day and keep a log of these recordings.” The EHV virus can present as respiratory disease or neurological disease, and in some cases can cause abortion. Early intervention can help ameliorate the disease and speed recovery time. Rigorous hygiene, and infection control mea- sures can help control the spread. This includes washing hands and changing clothing before handling other horses. Communication is vital to alert other horse owners that the horse has been in contact with. “We are learning more about the interaction between virus and bacteria,” says Gomez. “Usually, the virus enters the respiratory system, produces inflammation and decreases the defense mechanisms of the respiratory tract. When those mechanisms are not working any- more, pathogenic bacteria are able to colonize the respiratory tract.” The study demonstrates how fast the virus spread in the farm, how many animals can get affect- ed at the same time, and that this can have fatal consequences for the horses. A biosecurity plan is essential to practice infection control. The disease can spread by direct con- tact from one horse to another or Research Links Viral Infections Like EHV and Pneumonia by contaminated nasal secretions. EHV can also spread indirectly through contact with physical objects that are contaminated with the virus. Sharing of equipment between horses is discouraged. The air around the horses can be contaminated with infectious viruses; therefore it is important to have ample distance between paddocks and separate new horses and those returning from events. Gomez recommends quarantining new horses or those returning from an event for 21 days. In conclusion Gomez cautions owners that if a horse develops a fever and is found to be shedding equine herpes virus, then the level of risk to other horses on the prem- ises increases significantly. “If equine herpes virus is suspected the owner needs to immediately notify the veterinarian and do not move the horse or take the horse to another farm or to another event. The veterinarian can make a plan for testing and institute bio-safety measures in the farm.” Find out the biosecurity risk on your farm with the Biosecurity Calculator, available at equine- gulph.ca, search for biosecurity. TheHorsePortal.ca offers online courses in Sickness Prevention in Horses.