The Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) reported Sept. 4 that it has confirmed additional West Nile virus (WNV) cases in horses in that state.

The number of equine WNV cases in Texas now totals 13.

As of Sept. 3, the TVMDL can confirm horses in the following counties have tested positive for WNV:

  • Houston County
  • Atascosa County
  • Jefferson County
  • Roberts County
  • Sterling County
  • Parker County
  • Randall County
  • Liberty County
  • Scurry County
  • Hutchinson County
  • Taylor County
  • Nolan County
  • Trinity County

The majority of the affected horses were not previously vaccinated against WNV. One horse’s vaccination history was uncertain, but that animal exhibited classical muscle facilitation for two to three days before tests confirmed WNV.

West Nile is transmitted to horses via bites from infected mosquitoes. Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations; hyperesthesia (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. Equine mortality rate can be as high as 30-40%.

[brightcove videoid="3151235477001" title="Health Alert: West