West Nile Virus Confirmed in Texas Horses

West Nile Virus Confirmed in Texas Horses

Protecting horses from exposure to mosquitoes can help reduce their risk of contracting a mosquito-borne disease like West Nile virus.

Photo: Photos.com

The 2011 mosquito-borne disease season is in full swing as two Texas horses have tested positive for West Nile virus (WNV) in two different counties.

Jim Schuermann, staff epidemiologist for vectorborne and zoonotic diseases of the Zoonosis Control Branch of the Texas Department of State Health Services, said Aug. 18 that WNV was confirmed in a Grayson County and a Harris County horse.

"The infections were confirmed by the Texas Veterinary Medical Diagnostic Lab at Texas A&M University," he said. "The Grayson County horse survived, but the Harris County horse was euthanized."

Grayson County is located in Northeast Texas, and Harris County is in the Southeastern part of the state. No further information on the surviving animal's condition was available.

Last week, WNV was confirmed in horses in California and Nevada, and a Georgia horse tested positive for the disease in late July.

In 2010 the USDA's National Animal Health Surveillance System reported 125 confirmed WNV cases in 28 states. Clinical signs for WNV include flulike conditions where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia, or hypersensitivity to touch and sound; changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia (incoordination on one or both sides, respectively). Equine mortality rate can be as high as 30-40%.

The American Association of Equine Practitioners recommends vaccinating all horses against WNV as a preventative measure. In addition to vaccination, minimize mosquito populations by eliminating breeding and resting areas, and by keeping mosquitoes away from horses. For example, reduce or eliminate sources of stagnant or standing water in close proximity to horses, remove manure from areas near the horses, keep horses stalled during peak mosquito periods (i.e., dawn and dusk), use equine approved mosquito repellents or protective fly gear (i.e., fly masks or sheets), and place fans in barns or stalls to maintain air movement, as mosquitoes don't fly well in wind.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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