Fewer researchers are probing the mysteries of BSE, but new discoveries about the fatal disease continue.
One of those findings is possible genetic resistance among some animals, said Stefanie Czub, research manager at the Canadian Food Inspection Agency’s prion unit in Lethbridge, which detected Canada’s first BSE case in an Alberta cow 12 years ago.
She and her team purposely infect young cattle brains with various forms of BSE and monitor the course of the disease. The animals are closely related to one another and one seemed to show some resistance.
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“There seems to be an indication that there is something in the genetic susceptibility of cattle,” she said at the Alberta Livestock and Meat Agency’s annual meeting in Calgary June 16.
“We had not known that before.”
The laboratory has a herd of 150 Hereford-Angus cattle that are line-bred and, in some cases, inbred. New genetics are introduced only with artificial insemination, and the test animal that showed resistance was a result of this breeding.
“We didn’t know what an important tool we had in our hands until we got these results,” she said.
The sire is known and researchers hope semen is available so that more genetic testing can be conducted.
Considerable knowledge has been gained since 2003 about the nature of this terminal brain disease, but more work is needed to fill in gaps, she said.
Researchers have learned that atypical BSE behaves differently from the classical form. Test results are different, although the physical symptoms are ultimately the same: the brain does not function properly.
Infected animals are spooked by noise, light and touch, cannot walk properly and become increasingly agitated.
About 85 cases of atypical BSE have been found worldwide.
“There are countries where atypical BSE is the only form of BSE detected,” she said.
“Sweden is one of those unfortunate countries.”
Researchers want to know if eating contaminated feed derived from infected animal parts can pass on this form and if specified risk materials from an atypical case carry the same kind of infectivity as classical BSE. They also want to determine the age of BSE susceptibility with these different strains. Classical BSE affects young animals and shows up four to six years later.
Researchers know the classical form is not passed from mother to offspring and is not transmitted through soil, saliva or feces among herd mates. This makes it different from scrapie in sheep and goats and chronic wasting disease in cervids.
They also know that three percent of the animals in a herd may be infected.
“That makes our last case from spring 2015 so interesting and so devastating,” she said.
Canada’s most recent diagnosis was found in a cow born in 2009 on a farm where an earlier case had been discovered a few years before in an unrelated animal.
There were 12 cases of BSE worldwide last year, which was a considerable drop from 1997, when the United Kingdom had 37,200 confirmed cases.
Canada has had 20 cases since 2003, including two atypical and 18 classical. This includes a case found in the United States that traced back to an Alberta dairy herd.
BSE was linked to variant Creutzfeld Jakob disease in 1997, and 229 cases were reported between 1996 and 2014. Most were in the U.K., where patients had eaten contaminated beef.
barbara.duckworth@producer.com
