West Nile Virus confirmed in Delaware horse

DOVER, Del. – The Office of the State Veterinarian today announced the Delaware’s first case of West Nile Virus (WNV) in a horse in 2017. The infected horse was an 11-year-old Quarter horse mare residing in Kent County. The horse began showing signs of weakness in all four limbs on August 6.  The mare lost the ability to stand and was therefore euthanized on August 9. Samples were submitted to the Delaware Public Health Laboratory on August 10, which confirmed the diagnosis of WNV on August 14. The affected horse was not currently vaccinated against WNV.

West Nile Virus and Eastern Equine Encephalitis (EEE) 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 (although not always with WNV), 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 (DNREC) 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 Eastern Equine Encephalitis (EEE) in DNREC’s sentinel chickens, and detection of WNV in a wild crow, in July and August. So far in Delaware this year, no cases of WNV or EEE have been found in humans.

Vaccinate your horse against West Nile Virus and Eastern Equine Encephalitis

The State Veterinarian urges horse owners to contact their veterinarians as soon as possible, as we are 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 70-90% of cases, and WNV in 30% of cases.

Horse owners can take several 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 2-3 days if possible to remove any mosquito eggs or larvae.

For more information about WNV or EEE:
• Human health questions should be directed to the Delaware Division of Public Health, (888) 295-5156, or (302) 744-4990.
• Animal health questions should be directed to the Delaware Department of Agriculture at (800) 282-8685 (Delaware only) or (302) 698-4500. Ask for the Poultry and Animal Health Section.
• Questions about the state’s mosquito control program or mosquito biology should be directed to the Delaware Department of Natural Resources and Environmental Control’s Mosquito Control Section at (302) 739-9917.

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