Mosquitoes bug horses.
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And that can be deadly when the insects harbour West Nile virus. An article by Jennifer Dick.
Long days and warm breezes signal more carefree days ahead, but not for horse owners concerned about West Nile virus (WNV) outbreaks. They’re turning to the Ontario Veterinary College for help and finding answers to their concerns. Clinical studies professor Scott Weese is recommending a new vaccine now widely available in Canada to prevent the disease. “West Nile virus had many devastating outcomes in 2002,” he says. “Because it’s new to Ontario, we’re unsure what this year will bring. But the West Nile virus vaccine appears to be effective, and we’re recommending its use.”
Weese saw the results first-hand when the virus reached horses in Canada last summer, after affecting Africa and parts of Europe for almost 65 years. Spread by blood-sucking insects such as mosquitoes, WNV causes damage to the central nervous system in birds, humans, horses and some other spe-cies. It’s difficult to treat, and the results can be fatal. Last year, 75 cases of equine infection were reported in Canada, but Weese says the true number of cases is likely much higher.
Most healthy horses exposed to WNV will not show signs of disease. In others, symptoms appear after a five- to 14-day incubation period and progress rapidly. Of the unlucky few that develop the most seri-ous form, called encephalitis (inflammation of the brain), 30 to 50 per cent may die. Two symptoms of the virus, lack of appetite and co-ordination, make it difficult to treat an afflicted animal without expert care from a veterinarian. Affected horses can also be dangerous to work around. Last year, U of G veterinarians such as Weese treated 28 of the most severe con-firmed cases in horses. Even with the expert care the animals received, the virus was so advanced that the veterinarians could save only about 60 per cent of the patients they saw.
To help prevent a similar situation this year, the Ontario Veterinary College large animal medicine service is recommending that horse owners use the licensed vaccine now available. “We believe it’s important that all horses be vaccinated for West Nile virus,” says Weese. “With this preventive medicine, many horses will be saved.” Although vaccination is thought to be effective, he stresses that management will also play a role in protecting horses.
Keep-ing animals indoors during peak mosquito hours (dusk and dawn) and removing standing water from barn areas and neighbouring fields should minimize risk of exposure, he says.
