The Sudbury & District Health Unit (SDHU) reported Aug. 12 that a horse in the city of Greater Sudbury, Ontario, Canada, has tested positive for West Nile virus (WNV).

This is the second reported horse to test positive in the health unit’s service area and the first in more than a decade; the first local horse to test positive was reported in August 2004.

West Nile is spread through the bites of infected mosquitoes. The virus is established in Ontario and has been found in birds, mosquitoes, humans, and horses. Last year, there were more than 10 confirmed human cases of WNV in Ontario; the SDHU reported its first and only case of human WNV in 2006.

Clinical signs of WNV in horses 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 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%.

The clinical signs of WNV can be consistent with other important neurologic diseases such as equine encephalitis, rabies, and equine herpesvirus; therefore it is important to work with your veterinarian to get an accurate diagnosis through laboratory testing.

[brightcove videoid="3151235477001" title="Health Alert: West Nile Virus"]

Horse owners should also consult thei