In recent years, West Nile virus (WNV) has slowly spread toward central Europe, with cases confirmed in Hungarian horses since 2003. For the moment, however, a group of Czech researchers report that the disease rate appears to be remaining steady.

“West Nile fever is occurring and spreading (in humans, birds, etc.) now in some Mediterranean regions (such as Italy and Greece), Balkan states (such as Serbia), and Central European countries (Hungary),” said study author Zdenek Hubalek, PhD, of the Institute of Vertebrate Biology in the Academy of Sciences in Brno, in the Czech Republic. “In some of these countries it affects horses.”

West Nile is a viral disease transmitted to horses by infected mosquitoes. Clinical signs include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); 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%.

Results from surveillance studies investigating antibodies in horses’ blood showed that the virus is not yet threatening northern Europe, said Hubalek. However, veterinarians have confirmed the virus in horses as far north as Slovakia, he said