“Our perennial topic this morning is West Nile virus (WNV),” began Rocky Bigbie, DVM, MS, director of field veterinary services with Fort Dodge Animal Health, at the 2005 Western Veterinary Conference held Feb. 20-24 in Las Vegas, Nev. He also focused on myriad hot topics in equine veterinary medicine, discussing WNV vaccination guidelines, influenza vaccination challenge, vaccine care and handling, drug compounding, and the veterinarian’s role in detecting and fighting bioterrorism.

He began by reviewing some of the basics of WNV infection in horses, its life cycle and transmission, and its dynamics in herds. Almost all of the virus resides in the bird population; mosquitos become infected by feeding on infected birds, then they pass it on to horses and humans when they feed on them afterward, he said.

He showed a video of an affected, ataxic (incoordinated) horse to illustrate the severity of neurological compromise. The horse was shown in a field, where he kept floundering around in circles and falling with greater incoordination of the hindlimbs than the forelimbs. “This horse lived; he never lost the ability to get up, and that is often the discriminator between loss and survivability,” he reported. Mules and donkeys are just as susceptible to WNV as horses, he noted, adding that all horses are susceptible but older ones are more likely to die.

“Mortality may result from injuries incurred during acute disease, such as severe lacerations, head trauma, fractures, sepsis, or from an owner’s thin wallet (if an owner is unable or unwilling to provide the care these horses need to recover),” he added