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Equine Herpes Update and Biosecurity Guidelines

Contact: Don Hoenig, 207-287-7615

E-mail: Don Hoenig

The latest information on the EHV-1 situation in Maine is as follows:

1) To date, three horses have died at the Rome farm: a 17 year old died on March 18; a three year old was euthanized on March 19 and this horse was confirmed by lab tests as positive for the neurotropic form of EHV; a 30 year old died suddenly on March 28 after exhibiting seizures and no other apparent signs. Blood testing on this horse was inconclusive as there was an insufficient quantity of blood to accurately test.

2) The eight year old mare at the Wales farm tested positive for EHV-1 on both blood and nasal swab. She is currently continuing to recover. At both farms, temperatures are being monitored on all horse twice a day.

Quarantines at both farms will be in place for at least 21 days after the last clinical signs have resolved. It is likely that the Department will require some form of EHV-1 testing before the quarantines will be released but the exact nature of this protocol has yet to be determined. (According to Dr. George Allan of the University of Kentucky, there is no evidence that recovered horses pose any greater risk for infection of susceptible horses than a random assortment of animals). EHV-1 is present throughout most of the world and almost all horses older than two years of age have been exposed.

The most common means of transmission of EHV-1 is by direct contact with infected horses through aerosol transmission of droplets from coughing or snorting. Additionally, mares who have aborted will shed the virus in vaginal fluids and aborted fetuses are also sources of virus. Respiratory shedding generally lasts for seven to ten days but may persist for somewhat longer. Depending on the weather (viruses survive well in the cold, the damp and the dark and don’t survive long under hot, dry, sunny conditions), the virus may persist in the enviroment for several weeks. Inanimate objects such as grooming tools, water and feed buckets and contaminated clothing or footwear can also be potential sources of spread. Therefore, all horse owners and people who conduct business on horse farms (feed trucks, farriers, veterinarians, sales people, etc.) should practice strict biosecurity. This includes changing coveralls when traveling between farms, cleaning and disinfecting all equipment used when treating or handling horses and cleaning and disinfecting footwear or boots between farms. An excellent and cheap disinfectant solution can be made by adding five tablespoons of household bleach per one gallon of water. This should only be used after surfaces have first been thoroughly cleaned of all organic matter and dirt.

The issue of whether to continue to hold or participate in events such as shows, races, training courses, trail rides and other gatherings of horses should be carefully evaluated in consultation with your practicing veterinarian. Each case is unique and there is no one-size-fits-all approach that can be recommended. Previously, in consultation with a group of Maine veterinarians and equine professionals, the Department recommended that all fairs, race tracks and training facilities require EHV-1 vaccination, not less than 14 days or more than six months, before entering their facilities. While this group realizes that the role of the vaccine in preventing the neurologic form of EHV-1 is controversial, we nevertheless feel that vaccinating is a prudent measure at this time. Other states in the region have made similar recommendations. Your veterinarian can consult with you further on the specific type and timing of the vaccine.

For more information see http://www.maine.gov/agriculture/ahi/diseases/index.html

Biosecurity guidelines for EHV-1.