Alberta will no longer conduct extensive surveys regarding West Nile virus because of the low incidence of the disease in the province, said the province’s chief veterinarian.
While West Nile virus is still a reportable disease in Alberta, the agriculture department won’t conduct its post-illness surveys, said Gerald Ollis.
“What we have stopped is the survey of veterinarians and owners with regards to factors leading to West Nile occurring in the first place,” he said.
Three years ago, when there were 180 cases of West Nile disease in horses in Alberta, the province established the survey to find out more about the disease. Two years ago there was four cases and last year there were three confirmed cases of West Nile in horses.
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“The numbers are so small we can’t get any meaningful statistics out of it,” said Ollis.
When the survey was established the department hoped to get a clear picture of what factors were associated with West Nile. But with only three cases last year it’s difficult to draw conclusions about the disease in Alberta, he said.
The disease will continue to be reportable. One of the requirements to export horses to Japan is that the horses can’t have been within a certain distance of where West Nile has been detected.
Information from the study showed that nearly all the horses that developed West Nile were not vaccinated or not vaccinated properly or too soon in the mosquito season.
“We still think vaccination appears to be effective in preventing West Nile. We’re still recommending owners vaccinate their horses,” said Ollis.
Les Burwash with Alberta Agriculture’s horse industry branch said owners need to vaccinate their horses before the mid to the end of June, a month before the culex tarsalis mosquito comes out in Alberta.
“There is no question the vaccination has been a benefit to controlling the disease,” said Burwash.
A 2005 University of Saskatchewan study showed the odds of the disease appearing in unvaccinated horses was 31 times greater than for protected horses. The same study revealed that on farms that did not vaccinate any animals the disease was 85 times more likely to occur than on farms that vaccinated all animals.
