CHRONIC WASTING DISEASE: Infected brain tissue from deer will be injected into healthy cows to determine whether the disease can jump species.
MILWAUKEE – Scientists will soon inject brain tissue from deer infected with chronic wasting disease into the brains of healthy cattle to see whether the cows develop a similar disease.
Scientists in Ames, Iowa, will begin the experiment later this month to find out whether the fatal disease can cross the species barrier to infect cattle.
The experiment is of particular interest in Wisconsin, home of 1.6 million deer and 1.3 million cattle. So far, the state has found 40 deer infected with chronic wasting disease.
The scientists in Iowa will keep 20 Jersey calves in pens, where a ventilation system will filter out bacteria, said Janice Miller, a U.S. Department of Agriculture veterinarian in charge of the experiment.
They will inject each calf with a saline mixture that will include about one-tenth of a gram of diseased brain tissue from Wisconsin white-tailed deer.
Based on previous research, Miller said she believes it will be very difficult for chronic wasting disease to naturally jump to dairy cattle.
Still, “There is no way you can say ‘no risk.’ The way the research is piling up, I think you can say ‘low.’ In two years or three years or four years or five years, we’ll have some results,” Miller said.
Researchers likely will not have the final results of the experiment for several years. Next year, they plan similar experiments with pigs and sheep.
For nearly 250 years, a fatal brain disease now called a transmissible spongiform encephalopathy appeared to afflict only sheep. But in the past 60 years, mink, deer and cattle developed similar brain diseases.
Researchers believe changes in the way animals were fed, housed and recycled may have contributed to the development of the new diseases.
It was Richard Marsh, a scientist from the University of Wisconsin-Madison, who sounded a warning about questionable animal feeding practices more than a decade ago and kept sounding it until his death in 1997, even as critics dismissed him as an alarmist.
What worried Marsh was the feeding of rendered cattle and other ruminant animal products back to cattle, a practice widely blamed for the outbreak of mad cow disease in Great Britain.
“We caused these animals that are vegetarians to cannibalize themselves with these feeds,” Roger Viadero, the former inspector general of the U.S. Department of Agriculture, said in a recent interview. “To a large extent, man is responsible.”
About 130 people have died from variant Creutzfeldt-Jakob disease, believed to be the result of mad cow disease spreading to humans who ate infected beef.
The mad cow experience raised the possibility that other related diseases might infect people.
Experts say there is no scientific evidence chronic wasting disease can infect humans, but the World Health Organization advises people not to eat any part of a deer with evidence of the disease.
Today, some scientists suggest that humans may yet have an opportunity to repair the damage.
They believe genetic testing could reveal animals that are resistant to diseases such as mad cow and chronic wasting. Once identified, resistant animals could be bred in captivity and then used to repopulate herds after susceptible animals have been killed off. Veterinarians already have found a breed of sheep that appears resistant to the brain disease scrapie.
Theoretically, the same could be done for deer, said Gary Voelker, a research scientist with Infigen, a DeForest biotechnology firm and one of the country’s leading animal cloning companies.