CWD research increases as US concern grows

CWD could be on the rise.

Scientists working on chronic wasting disease (CWD), which affects deer and elk, are finding their finances suddenly bolstered. “CWD has become of national interest for several reasons,” says Edward Hoover, a CWD researcher at Colorado State University, “the recognition of [bovine spongiform encephalopathy (BSE)] in Europe; CWD has spread east of the Mississippi valley; and the farmed deer and elk industry has been seriously affected.”

CWD is a fatal brain disorder from the class of transmissible spongiform encephalopathies (TSEs), which include BSE in cattle, scrapie in sheep and Creutzfeldt–Jakob disease in humans. Hoover heads a new center dedicated to CWD established with a 7-year, $8.4-million grant from the National Institute of Allergy and Infectious Diseases (NIAID). The National Institutes of Health has requested $26.4 million for TSE research in FY2003, a 9% increase over the previous year.

Until recently, CWD, which was first identified in 1967, was thought to be confined in the wild to a relatively small region of northeastern Colorado. But earlier this year it was discovered in other areas, including Wisconsin and South Dakota, and the Canadian province of Saskatchewan. It is not clear how fast the disease is spreading, but in Wisconsin, where 40 infected deer have been found, state officials want hunters to kill a herd of 25,000 deer to eradicate the disease.

In scrapie, rogue prion proteins accumulate in the placenta, suggesting that this organ is the source of contamination, but in CWD, the source of infection remains elusive. “One primary interest is to determine if CWD is contained in urine, feces, saliva and other bodily secretions,” says Hoover, whose group will use antibody-based assays to look for CWD prions in these materials.

An even more pressing question is whether other animals are susceptible to CWD—in particular, cattle and people. Five years ago, Janice Miller, a researcher with the US Department of Agriculture, injected material from infected mule deer into the brains of cattle and 4 out of 14 animals have developed “a prion disease.”

But there is no evidence, as yet, that the disease is transmitted through feeding, the likely mode of transmission in the wild. Elizabeth Williams at the University of Wyoming fed cattle CWD-infected tissue. Five years later “we don't see any evidence of transmission,” says Williams, who plans to monitor the cows for another five years. In addition, scientists at NIAID's Rocky Mountain Laboratories will investigate whether the rogue CWD prion protein can be transmitted to monkeys who eat meat containing abnormal CWD prion proteins.