Ohio, Idaho and Delaware Report Equine WNV Cases

New cases of equine West Nile virus (WNV) have been reported in these states.

Three states have reported new cases of West Nile virus (WNV), with two of four reported as being euthanized.


The Delaware State Veterinarian has confirmed two cases of West Nile virus in Kent County. 

A 3-year-old Standardbred mare at a private facility showed an onset of clinical signs on August 19, 2018, including ataxia. Diagnostic testing at the National Veterinary Services Laboratory confirmed WNV. The vaccination status of the horse is unknown. 

An unvaccinated 2-year-old Thoroughbred filly at a private facility showed an onset of clinical signs on August 24,  including fever, mild ataxia, pharyngeal paralysis, flaccid tongue, inability to swallow a nasogastric tube, and a stuporous demeanor. The horse is receiving treatment.


The Idaho State Veterinarian has confirmed a case of West Nile virus in Jerome County. A 10-year-old Quarter Horse stallion at a private facility showed an onset of neurological signs on August 24, including ataxia, subsequent recumbency and inability to rise. PCR on blood at University of California Davis confirmed WNV. Vaccination status is unknown and the horse was euthanized. 

This is Idaho’s third confirmed case of equine WNV in 2018.


The Ohio Department of Agriculture confirmed a case of West Nile virus in a 3-year-old Standardbred mare in Holmes County. On August 18, the horse exhibited stiffness, lip droop, tremors and ataxia over a five-day period and was unresponsive to medical therapy. The horse was euthanized on August 22. 

After determining that brain tissue was negative for rabies, PCR assay at the Ohio ADDL detected WNV nucleic acid in brain stem tissue of this horse. The horse was not vaccinated against WNV. 

This is the second WNV-positive horse from Holmes County and the fourth case in Ohio in 2018.

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