NISKU, Alta. – Chronic wasting disease hasn’t been found in wild deer and elk in Manitoba and Alberta but that doesn’t mean the likelihood of the disease is any less than in Saskatchewan, said a Saskatchewan veterinarian.
“There is a reasonable probability CWD in Alberta and Manitoba is the same as Saskatchewan, given the sample sizes in those provinces,” said Trent Bollinger of the Canadian Co-operative Wildlife Health Centre at the University of Saskatchewan in Saskatoon.
“The absence of evidence is not evidence of absence,” Bollinger told a CWD conference.
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There have been no positive cases of the disease in wild deer and elk in Alberta and Manitoba. In Saskatchewan, seven wild deer have tested positive for CWD.
Bollinger said that doesn’t mean there is more disease in Saskatchewan, because fewer animals have been tested in Alberta and Manitoba. In Saskatchewan 7,678 wild deer and elk have been tested, while 2,632 have been tested in Alberta and 1,050 in Manitoba.
In the existing samples, the disease appears to be clustered. When a positive is found, more intensive testing is done around the area where the animal was found, increasing the probability of detecting the disease, he said.
“In order to say with more confidence there isn’t the disease in Manitoba or Alberta, there has to be more intensive sampling.”
In the United States, CWD has been found outside the areas where it was previously found. This can be partly attributed to the movement of infected animals, but some of the spread is the result of increased surveillance of the disease in farmed and wild cervids.
“We don’t know when it arrived in those areas because we weren’t looking for it before,” he said.
Using the Saskatchewan samples, Bollinger said researchers can say with 95 percent confidence that the disease in the wild population is between .03 and .15 percent.
In Alberta, there is a 95 percent confidence rate the disease is not greater than .11 percent in the wild herd.
In Manitoba there is a 95 percent confidence level the prevalence of the disease is not greater than .29 percent.
