RED DEER – West Nile virus reached epidemic levels last year.
As of Nov. 24, 2,325 Canadians had been diagnosed with the disease and eight people died.
“From a human perspective in 2007 we exceeded our epidemic year,” said veterinarian Dr. Larry Frischke of Wyeth Animal Health, one of three companies to develop a West Nile disease vaccine for horses.
“That has not been recorded anywhere else in North America.”
Frischke told an Alberta horse breeders conference in Red Deer Jan. 12 that 121 horses were diagnosed last year.
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Saskatchewan had the highest number of cases – 1,422 people and 57 horses. In Alberta 320 people and 46 horses tested positive. Manitoba had 576 human cases and eight horse cases. British Columbia has never had a case.The last serious outbreak was in 2003 when infections peaked in Saskatchewan and Alberta.
There was a dramatic drop in cases in 2004 because of a cool summer. The culex tarsalis mosquito is a heat loving insect and spreads the disease to birds, animals and people.
“Over the years the incidences tend to be late summer when we have more heat to get this mosquito population going,” he said.
The earliest cases were diagnosed last year at the end of June.
“We also know when we come off a peak incident year, most of the animals out there have been exposed,” Frischke said.
The birds either die or gain immunity for a year. Among horses contracting the disease, 30 percent are likely to die and others have lingering problems.
Horse cases appear to be dropping because of a successful vaccine campaign. They are protected when two doses of vaccine are administered with a booster each year. There is no vaccine for people.
The disease was first reported in New York in 1999 and has spread across most of Canada and the United States.
