A 24-year-old Quarter Horse mare in Grand County, Colorado, tested positive for West Nile virus (WNV) on Sept. 30. Despite being vaccinated, the horse developed clinical signs on Sept. 24, such as weakness, ataxia, teeth grinding, abnormal mentation, and inability to rise, leading to her euthanization.
EDCC Health Watch is a marketing program by Equine Network that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization supported by industry donations to provide open access to infectious disease information.
WNV 101
West Nile virus is transmitted to horses through bites from infected mosquitoes. Clinical signs in infected horses can include flulike symptoms, muscle twitching, hypersensitivity, changes in mentation, drowsiness, propulsive walking, spinal signs, and ataxia.
- Flulike symptoms
- Muscle and skin fasciculation
- Hyperesthesia
- Changes in mentation
- Drowsiness
- Propulsive walking
- Spinal signs
- Ataxia
There is no cure for West Nile virus in horses, and mortality rates can be as high as 30-40%. Vaccination is an effective prevention method, with annual booster shots recommended for previously vaccinated horses and a two-shot vaccination series for unvaccinated horses.
In addition to vaccinations, owners should take measures to reduce mosquito populations and limit horses’ exposure to mosquitoes by removing stagnant water sources, cleaning water buckets regularly, keeping animals indoors during peak insect feeding times, and using approved mosquito repellents for horses.