Researchers closer to chronic wasting disease vaccine

Chronic wasting disease is spreading among wild deer and elk but researchers are hopeful a vaccine could be developed to control the fatal condition.

Scientists at the University of Calgary’s faculty of veterinary medicine published results on a possible vaccine that was tested on modified mice to prolong the time before infected animals developed the terminal brain-wasting disease.

It is a challenging form of vaccine, said Hermann Schaetzl, head of the Calgary prion research unit.

“This is a disease the immune system doesn’t really see, so we have to make it visible to the immune system,” he said.

It is like a killed vaccine using recombinant protein to ultimately stimulate an immune response.

“We want to interfere with the infection so animals that are vaccinated do not develop the disease or are protected so it takes much longer so they can live longer,” he said.

Further work is exploring ways to interfere with the spread of the disease among live animals, which pass the disease via body secretions like urine, saliva and feces that are picked up by susceptible animals.

“We would like to interfere with our vaccine so they produce less prions which go into the environment so that the possibility for uninfected deer and elk to get infected is slower,” he said.

Hypothetically, this disease could jump the species barrier to infect people who consume game, so if the population is vaccinated, the risk is reduced. However, it has not been proven to be zoonotic.

The pathology is similar to BSE, which causes holes in the brain and deposition of pathological prions.

Infected animals lose weight, stumble or pace, show a lack of co-ordination and drool. CWD is fatal in all cases and there is no cure, treatment or prevention.

Schaetzl has been studying prion diseases since 1993 and worked in Wyoming from 2010-13 before coming to Canada.

It is not a new disease and was first seen in Colorado and Wyoming in the 1960s. It is part of the family of transmissible spongiform encephalopathies like BSE in cattle, scrapie in sheep and Creutzfeld Jakob disease in humans.

“Nobody has an idea why we have CWD, where it is coming from and when did it really start,” he said.

It is hard to determine how widespread the disease is in wildlife, but it is suspected there are parts of Wyoming and Colorado where about half the deer and elk in some regions are infected.

“The prediction is at the moment when you have higher than 25 percent of infected animals in a herd … at the end, the herd could become extinct,” he said.

Canada is not at this stage but the incidence rate has doubled during the last few years.

In Alberta, prevalence is probably about three to five percent but the disease is expanding in infection levels, as well as geographic range so it could move north and infect caribou, said Schaetzl.

It is a reportable disease in Canada and wildlife surveillance programs encourage hunters to submit heads for testing. Last year, about 350 cases were found in Saskatchewan. Alberta detected the disease in 360 deer, primarily mule deer males, as well as some elk. About 6,000 heads are tested annually.

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