Chronic wasting studies announced

The US Department of Health and Human Services (DHHS) is stepping up efforts to determine whether Chronic Wasting Disease (CWD), a fatal brain disease spreading rapidly in deer and elk throughout North America, could pose as great a risk to human health as "mad cow" disease. Two new studies announced November 4 by the Food and Drug Administration (FDA), and another set of inquiries recently commissioned by the National Institutes of Health (NIH), will focus on how likely the disease is to jump species barriers among animals and even to humans.So far, necropsies of hunters whose deaths raised suspicions of CWD infection have returned negative results. However, concerns persist and CWD has already been found in at least 10 states and parts of Canada. Up to 15 percent of mule deer in herds ranging across northern Colorado and southern Wyoming have the disease, according to Greg Raymond at the NIH Rocky Mountain Laboratories in Hamilton, Montana. CWD is a transmissible spongiform encephalopathy (TSE), similar to bovine spongiform encephalopathy (BSE), or "mad cow" disease, in cattle, scrapie in sheep, and Creutzfeldt-Jakob Disease (CJD) in humans. A hallmark of a TSE is the presence of abnormally folded prion proteins, or PrPSc, which convert their normal counterparts in brain and lymph tissue, PrPC, and are more resistant to enzyme digestion. An infected animal can incubate a TSE for years before it shows symptoms. One of the two FDA-commissioned studies will be conducted at Case Western Reserve University in Cleveland, Ohio. Led by Pierluigi Gambetti, and jointly funded by FDA and the Centers for Disease Control and Prevention (CDC), the study will use mice as an animal model to see how likely the disease is to jump the species barrier. Another set of studies by the Harvard Center for Risk Analysis will use earlier findings regarding how BSE might spread if introduced in the US to assess the potential spread of CWD. There is no indication so far that CWD has jumped from deer to humans, according to epidemiologist James Kazmierczak at the Wisconsin Division of Public Health. Three suspicious deaths from 1993 to 1998 involved men who shared venison meals in Wisconsin. One who died in 1993 was ruled out for prion disease, but tests on the other two men are still pending at the National Prion Disease Pathology Surveillance Center at Case Western. The National Institute of Allergy and Infectious Diseases (NIAID) also recently commissioned studies into CWD, awarding a seven-year, $8.4 million contract to researchers at Colorado State University and the University of Kentucky. Glenn Telling at University of Kentucky is working with transgenic mice that express deer and elk alleles to study CWD transmission and susceptibility across species. A key factor for conformation conversion of prions across species is how closely matched PrP sequences are.The scientists will also try to find out how CWD transmits across species in the wild, something they do not yet know, Telling said. "We'll study how saliva, urine or other excrement might serve as modes of transmission, and measure infectivity from various body tissues from infected deer and elk," he explained. Research begun five years ago by Randall Cutlip at the US Agricultural Research Service (ARS) is examining possible transmission of CWD to cattle. To date, only one cow inoculated with CWD from mule deer was found to have prion disease at necropsy, but all four of the animals that died had variable clinical signs unlike either BSE or scrapie and no microscopic lesions in brain tissue, according to Janice Miller of ARS. Five more intracerebrally inoculated animals remain healthy.

Chronic wasting studies announced

US orders new examinations of human risk from prion disease in deer and elk.

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