Fatal Equine WNV Case Reported in Alabama

The Alabama Department of Public Health (ADPH) has confirmed an equine case of West Nile virus (WNV) in the city of Boaz, in Marshall County. According to a July 15 Equine Disease Communication Center report, the WNV case involved a 3-year-old Mammoth Mule, which was confirmed positive for the disease on June 28 and subsequently euthanized after showing signs of ataxia (incoordination) and becoming recumbent. The mule had not been vaccinated against WNV.

WNV transmission occurs when infected mosquitoes feed on animals, as well as humans, after having fed on infected birds. This is the first WNV case reported for this year in the state, according to a statement released by ADPH. No human infections have been reported, but the risk will remain through the active mosquito season, the release said.

“Positive cases in veterinary species, such as horses, can serve as a reminder that infected mosquitoes are circulating and people can be at risk,” said Alabama State Public Health Veterinarian Dee W. Jones, DVM. Jones stressed that people only get infected from mosquitoes and that horses do not pose an additional risk for human infection.

Clinical signs of WNV in horses include:

• Flulike signs, where the horse seems mildly anorexic and depressed;
• Fine and coarse muscle and skin fasciculation;
• Hyperesthesia (hypersensitivity to touch and sound);
• Changes in mentation (mentality), when horses look like they’re daydreaming or “just not with it”;
• Occasional drowsiness;
• Propulsive walking (driving or pushing forward, often without control); and
• Spinal signs, including asymmetrical weakness; and
• Asymmetrical or symmetrical ataxia.

West Nile virus has no cure; however, some horses can recover with supportive care. Equine mortality rates can reach 30-40%. The American Association of Equine Practitioners includes WNV as one of the core diseases all horses should be vaccinated against at least annually.