Owners Urged to Vaccinate Horses against West Nile Virus

Owners Urged to Vaccinate Horses against West Nile Virus

State officials urge owners to remain vigilant and to vaccinate their horses to keep the number of confirmed equine WNV cases low.

Photo: Erica Larson, News Editor

Warm weather and the start of mosquito season are underway, and the Maryland Department of Agriculture (MDA) is urging horse owners to vaccinate their horses against potentially fatal mosquito-borne diseases, including West Nile virus (WNV).

“Preventing a disease is always less expensive and traumatic than treating it, so we urge horse owners to be proactive now that the weather is warming up and vaccinate their horses,” said Maryland State Veterinarian Guy Hohenhaus, DVM. “Your veterinarian is the best source of information and advice for your horse and its health. We also remind veterinarians across the state that they must report any cases of equine arboviruses (or mosquito-borne diseases) to MDA.”

Horse owners who have vaccinated their horses against other arborviruses, such as Eastern equine encephalitis (EEE), Western equine encephalitis, and Venezuelan equine encephalitis, still need to get their horses vaccinated for WNV, as these are different viruses and those vaccinations do not provide cross-protection.

West Nile is a serious and, at times, deadly disease that affects humans and horses. Clinical signs of WNV in horses include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia (hypersensitivity to touch and sound); changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional drowsiness; propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia (incoordination). Equine mortality rate can be as high as 30-40%.

In 2003, there were 234 cases of equine WNV reported in Maryland; however, that number has decreased sharply with only 12 equine cases reported between 2004 and 2013. State officials urge horse owners to remain vigilant and to vaccinate their horses to keep that number low. State veterinarians also encourage horse owners to vaccinate their horses against rabies and EEE.

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