THURSDAY, Feb. 20, 2003 (HealthDayNews) -- Three men who ate wild game in a northern Wisconsin cabin all died of what appeared to be similar neurological symptoms.
Were the cases some kind of "mad deer" disease, acquired from eating contaminated venison?
The U.S. Centers for Disease Control says "no" in this week's Morbidity and Mortality Weekly Report, but the agency is not ruling out the possibility that so-called chronic wasting disease (CWD), found primarily in deer and elk, could be transmitted to humans.
The findings are the conclusion of an investigation, started in August 2002, into the deaths. Two of the men died in 1993 and the third died in 1999.
Chronic wasting disease, along with mad cow disease and its "human equivalent," Creutzfeldt-Jakob disease (CJD), belong to a family of illnesses called transmissible spongiform encephalopathies (TSEs) or "prion diseases." All are believed to be caused by a protein called a prion. While normal prions are present in the human body and are harmless, prions folded into a different shape can cause dementia and death.
Because mad cow disease appears able to cross over from cows to humans, officials have been concerned that other prion diseases can do the same.
CWD, which was first described in the 1960s and classified as a prion disease in 1978, was originally confined to deer and elk in an area in northeastern Colorado and southeast Wyoming. Since 2000, however, the disease has been found in free-ranging deer in parts of Illinois, Nebraska, New Mexico, South Dakota and Wisconsin as well as new areas of Colorado and Wyoming. It's also been found in captive deer and elk in Colorado, Kansas, Minnesota, Montana, Nebraska, Oklahoma, South Dakota and Wisconsin.
Officials are not sure how the disease is spread from animal-to-animal. Right now, says Dr. Robert Ehlenfeldt, acting state veterinarian for the state of Wisconsin, "there's no evidence that this is at all transmissible to people or to livestock species, so cattle don't get this disease."
The first death to concern Wisconsin Department of Health officials occurred in February 1993. The man was an avid hunter and owned a cabin in northern Wisconsin, where he had hosted regular wild game feasts since 1976. The meals consisted of elk, deer, antelope and other game probably caught in nearby areas of Wisconsin.
The man had a history of seizures dating back to 1969. But, at the end of 1992, he developed more seizures, along with forgetfulness and hand tremors. He died in a matter of months. While his symptoms were consistent with Creutzfeldt-Jakob disease, prion tests came out negative.
The second man, also from Wisconsin, died in August 1993 after developing slow speech, a deteriorating memory and personality changes. He had been a hunter, participated in the wild game feasts and apparently consumed a lot of venison. In this case, tests confirmed that he did not have CJD.
The third man, a Minnesotan who died in July 1999, had suffered dementia and speech abnormalities, which were provisionally diagnosed, again, as CJD. Although the man didn't hunt, he had visited the cabin an estimated 132 times and had participated in one feast in the mid 1980s. A prion test came back positive: This man did have CJD.
Health officials said that it's not clear how the man with CJD acquired the disease. Some 85 percent of CJD cases are "sporadic" and have no known cause.
"There's no evidence that his CJD was unusually acquired," Dr. Charles Hsu, a medical epidemiologist with the CDC's National Center for Infectious Diseases in Atlanta, says.
The officials also aren't clear on what caused the other two deaths.
"We do not know the exact diagnosis of the other two gentleman," Hsu says. "The problem with the surveillance laboratory that did the tests, their main focus is to determine whether it's a prion and if it's not, they don't go further."
As it turns out, the men probably did not eat venison from a so-called "endemic" area, where more cases are concentrated.
None of which is to say that the mystery of CWD and CJD is over.
"Unfortunately, our investigation is just a small piece of the larger puzzle that still needs to be resolved," Hsu says.
Officials are hoping that heightened awareness of these findings will prompt physicians to send suspected cases of CJD to the surveillance laboratory to be analyzed.
In the meantime, experts are advising certain, common-sense precautions.
"You shouldn't eat meat from any animal that's showing clinical signs of any disease. It doesn't matter whether it's CWD or some persistent diarrheal disease or anything else. It's not a good idea," Ehlenfeldt says.
And you should also stay clear of the portions of an animal carcass that might contain prions. "Prions are only found in the brain and eye, spleen and lymph nodes, not in the meat," Ehlenfeldt says.
Hunters should not cut through the spinal cord of the carcass. Lymph nodes under the skin should be discarded with the hide.
Above all, the CDC officials stress, don't panic. "As far as we know, it's staying in animals," Hsu says.
More information
The Wisconsin Department of Agriculture, Trade and Consumer Protection has information on chronic wasting disease.
Try the National Institute of Neurological Disorders and Stroke for information on Creutzfeldt-Jakob disease.
