The most important piece of information to be learned during the investigation into Canada’s latest BSE case is not where the cow was found.
“The important thing is when was it born: before the extended feed ban, which was 2007, or was it born after the extended feed ban? Then I think one has to look very carefully how this cow has acquired infection,” Hermann Schätzl, a professor of prion biology and immunology at the University of Calgary’s faculty of veterinary medicine said Feb. 13.
It takes five to 10 years before symptoms appear once the disease sets in.
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Canada’s last reported case was in 2011. That cow was born in 2004.
The age of the cow in this latest case could determine whether it is the classical form of the disease linked to eating contaminated feed or a sporadic or atypical form, Schätzl said.
The disease has been linked to adding contaminated bovine meat and bone meal as an added source of protein in cattle rations. Canada placed a ban on using these products in 1997 and strengthened the restrictions in 2007.
The classical form of BSE is associated with feed, while sporadic cases in older animals show up worldwide.
Alberta is one of the world’s primary prion research areas, and considerable data has been collected since the first Canadian born case was diagnosed in Canada.
Prions are abnormal forms of protein responsible for fatal brain diseases in humans, cattle, cervids, sheep and some other minor species.
“These kinds of diseases are known quite well, particularly the infectious forms like BSE,” Schätzl said.
“We know what the risk factors are, we know how infection starts and the end product is always a fatal disease.”
At risk are animals that received contaminated feedstuffs at an early age. Diseased, down or dead cattle older than 30 months are eligible for testing.
“We have very good diagnostics,” he said. “The prevention worked very well in Europe. BSE is basically almost gone.”
However, there are no live tests or treatment for sick animals. Occasional positive cases still show up, but they are scattered.
“The problem with prion diseases is that you never get rid of them,” he said.
In Europe, every bovine brain was tested at three years of age, which was later changed to four years or older. Germany tested more than 11 million animals older than 24 months, and a couple cases were found in younger animals.
No one is sure where classical BSE originated. Some speculated during the early stages of the epidemic in England 25 years ago that it was linked to adding rendered meat and bone meal from scrapie infected sheep into the feed supply.
“It was more likely it was already in cattle and never posed a problem because they were not feeding cattle to cattle,” Schätzl said.
He and his colleagues are working with models to propagate the prion diseases for study. He has studied prion related diseases since 1993 and hopes to eventually develop an oral vaccine for cervids to prevent chronic wasting disease.
