The Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) has confirmed West Nile virus (WNV) in a horse located in south Texas and additional cases of Eastern equine encephalitis (EEE) in horses residing in east Texas.

This is not the first case of WNV in Texas in 2015; the first recorded positive was in a Houston County horse on July 2. However, the most recent positive comes from a horse in Atascosa County, south of San Antonio.

The Atascosa County horse exhibited mild lameness when ridden and when taken to the veterinarian, presented at a low-grade fever but no other classic WNV clinical signs. The horse’s veterinarian requested a variety of blood tests (including WNV, EEE, Western equine encephalitis, and Venezuelan equine encephalitis.) to determine the cause; WNV was the only positive result from this animal.

West Nile is a viral disease that normally cycles between wild birds and mosquitoes. As the virus infection rate increases in birds it is more likely to be transmitted by an infected mosquito that bites horses and humans. The virus abruptly attacks the central nervous system. As a reportable zoonotic disease, the Texas Animal Health Commission (TAHC) was made aware of the positive test results. Human infection with WNV is known to occur in the United States. However, horse to human transmission is not a concern