More than 400 equine cases of West Nile virus (WNV) have been confirmed nationwide this year, according to the USDA Animal and Plant Health Inspection Service (APHIS). The current total marks a 372% increase in cases compared to last year’s total.

On Oct. 2, APHIS statistics revealed 411 confirmed equine WNV cases; in 2011, just 87 confirmed cases were reported nationwide. Texas, Louisiana, and Pennsylvania have reported the most cases thus far, with 62, 50, and 36, respectively. As of Oct. 2, only seven of the contiguous states remained WNV-free: Delaware, Kansas, Maine, New Hampshire, Vermont, Virginia, and West Virginia. Alaska and Hawaii have never reported any equine WNV cases.

On Oct. 4, North Dakota State Veterinarian Susan Keller, DVM, told TheHorse.com that 15 cases of equine WNV have been reported this year in that state, compared to just one in 2011, although the actual number of cases could be higher.

"Many horses are treated and not tested, and there are likely many that are not even taken to a vet or the signs are mild and the case goes unnoticed," she relayed