Cattle Resist CWD in Long-Term Trial

Cervids, such as these young mule deer, can contract and transmit chronic wasting disease. ( John Maday )

Because of its similarity to Bovine Spongiform Encephalopathy (BSE), concerns have lingered that chronic wasting disease (CWD) in deer and other cervids could eventually could spread to cattle.

So far though, there has been no strong evidence that CWD can cross species barriers to affect cattle through typical environmental exposure, or for that matter, humans who consume meat from infected cervids. New results from a long-term exposure trial now support the belief that the lethal prion disease is highly unlikely to spread to cattle.

In this 10-year trial, researchers from the University of Wyoming’s Wyoming State Veterinary Laboratory (WSVL), the Colorado Division of Parks and Wildlife and the Wyoming Game and Fish Department (WGFD) collaborated to expose groups of cattle to high levels of CWD prions. The researchers exposed cattle to CWD using two methods and in different locations in Colorado, Wyoming and at the USDA’s National Animal Disease Center in Ames, Iowa. One group of 12 calves received an initial oral dose of brain material from CWD-infected mule deer, with five un-inoculated cattle serving controls.

Two other groups of cattle spent 10 years housed in outdoor pens with CWD-infected mule deer or elk, with continuous exposure through feed, water and direct contact.

At the end of the trial, the researchers euthanized and examined all the surviving cattle. None of the cattle showed any sign of CWD or any neurological pathology during the trial period or at necropsy.

As with other transmissible spongiform encephalopathy (TSE) diseases, CWD can develop slowly, with exposed animals remaining healthy for years before showing clinical signs. Thus, a long-term trial using environmental exposure similar to what occurs in the field, helps answer critical questions about the potential for the disease to cross species barriers.

The research report, titled “Cattle (Bos taurus) Resist Chronic Wasting Disease Following Oral Inoculation Challenge for Ten Years Natural Exposure in Contaminated Environments,” will be published in the July issue of the Journal of Wildlife Diseases.

For more, read CWD Concerns Persist from