West Nile Virus


AAEP Core Vaccination


West Nile virus (WNV) is the leading cause of arbovirus encephalitis in horses and humans in the United States. This virus has been identified in the entire continental United States, most of Canada and Mexico. The virus is transmitted from avian reservoir hosts by mosquitoes to horses, humans and a number of other mammals.

Clinical signs include:

  • Ataxia (incoordination) Stumbling
  • Loss of appetite Fever
  • Muscle-twitching Partial paralysis
  • Neurologic signs may include head-pressing,inability to stand up, convulsions and possibly death

The case fatality rate for horses exhibiting clinical signs of WNV infection is approximately 33 percent. According to AAEP, there is data showing that 40 percent of horses that survive the acute illness caused by WNV still exhibit residual effects, such as gait and behavioral abnormalities, six months post-diagnosis.

Other AAEP Core Vaccinations: