The Office of the State Veterinarian announced Aug. 16 Delaware’s first case of West Nile Virus in a horse in 2017.

The infected horse was an 11-year-old quarterhorse mare residing in Kent County. The horse began showing signs of weakness in all limbs Aug. 6. The mare lost the ability to stand and was euthanized Aug. 9. Samples were submitted to the Delaware Public Health Laboratory on Aug. 10, which confirmed the diagnosis of WNV on Aug. 14. The affected horse was not currently vaccinated against WNV.

West Nile Virus and Eastern Equine Encephalitis are diseases transmitted to horses via the bites of mosquitoes. Humans can also be infected with WNV and EEE, but transmission requires a mosquito bite and the virus cannot be directly transmitted between horses, or between horses and people. Signs of infection in horses include fever, anorexia, head pressing, depression or personality change, wobbling or staggering, weakness, blindness, convulsions, muscle spasms in the head and neck or hind-limb weakness. If owners notice any of these signs in their horses, they should contact their veterinarian immediately.

This is the first confirmed case of WNV in a horse in Delaware since 2015. However, The Department of Natural Resources and Environmental Control’s Mosquito Control Section, in conjunction with the Delaware Division of Public Health Laboratory and the Department of Agriculture, announced two detections of WNV and one detection of EEE in DNREC’s sentinel chickens and detection of WNV in a wild crow, in July and August. No cases of WNV or EEE have been found in humans.

The Office of the State Veterinarian urges horse owners to contact their veterinarians, as the state is in the midst of peak mosquito season, to have horses and other equines vaccinated against WNV and EEE. Neither disease has a specific drug treatment, and EEE infections in horses are fatal in 70 to 90 percent of cases and WNV in 30 percent of cases.

Horse owners can take additional steps in the barn and around the farm to help protect horses from mosquito bites. Horses should be kept inside during dawn and dusk, which are peak hours for mosquito activity. Topical insect repellents labeled for use on horses may be applied. The wind generated by fans installed in horse stalls can also help deter mosquitoes. Old tires and containers should be disposed of and standing water eliminated. Water troughs or buckets should be emptied, cleaned and refilled every two to three days if possible to remove any mosquito eggs or larvae.