Delaware Confirms First Cases of West Nile Virus in Horses

DOVER, Del. – The Delaware Department of Agriculture has confirmed the first two cases of West Nile Virus in Delaware horses this year.

The two cases include a 4-year-old Standardbred gelding and a 7-year-old Standardbred mare, both of which resided in Kent County and were euthanized. The onset of symptoms in these cases occurred between Aug. 31 and Sept. 1.

West Nile Virus is a disease transmitted via mosquitoes, with a peak period for disease transmissions from mid-August to mid-October. Signs of infection in horses include fever, anorexia, head pressing, behavior changes, wobbling or staggering, weakness, blindness, convulsions, muscle spasms in the head and neck, and/or hind-limb weakness. If owners notice any of these signs in their horses, they should contact their veterinarian immediately, as the West Nile Virus has a fatality rate of 30 percent in horses.

Humans can also be infected with West Nile Virus via mosquito bite, but the virus cannot be directly transmitted between horses or between horses and people.

Horse owners can take several precautions to minimize the risk of mosquitoes coming into contact with their horses. For starters, horses should be kept inside during dawn and dusk; the peak hours for mosquito activity. Topical insect repellents labeled for use on horses may be applied, and fans installed in horse stalls can also help deter mosquitoes. Water troughs and buckets should be emptied and cleaned regularly to prevent making breeding grounds for mosquitoes. The State Veterinarian also urges horse owners to ensure they add the West Nile Virus vaccine to their annual vaccination schedule. 

To report suspected cases of human West Nile Virus, contact the DPH Office of Infectious Disease Epidemiology at 302-744-4990 or email reportdisease@delaware.gov. Animal health questions should be directed to the Delaware Department of Agriculture at 302-698-4500.