Testing for chronic wasting disease

The state veterinary diagnostic laboratory, the Texas A&M Veterinary Medical Diagnostic Laboratory, TVMDL, stands ready for the increase in chronic wasting disease, CWD, testing needs due to an increase in CWD cases in Texas.

Due to the most recent detection of cases of CWD at deer breeding facilities, an emergency order to restrict deer movement across the state has been enacted by the Texas Parks and Wildlife Department, and the Texas Animal Health Commission is joining the effort to address the risks and managing strategies.

While ranchers and breeders are navigating new guidelines, TVMDL is preparing for an increase in CWD test submissions as a result of the emergency order.

What is Chronic Wasting Disease?

CWD is a naturally occurring transmissible spongiform encephalopathy, TSE, or prion disease similar to bovine spongiform encephalopathy, BSE, in cattle and scrapie in sheep and goats. Prions are abnormal proteins and extremely difficult to destroy. Once infected, the prions initially affect the animal’s lymph nodes and after spreading through the body, eventually infect the brain.

CWD is a progressive neurological disease that affects several cervid species, including white-tailed deer, black-tailed deer, mule deer, elk, red deer, reindeer, sika and moose. Since it was first reported in 1967, it has been documented in both captive and free-ranging cervid species in 26 U.S. states and three Canadian provinces.

CWD is slow developing. An affected animal may take several years to develop clinical signs of the disease. Clinical signs include weight loss, drooling, stumbling, stupor and lack of coordination. This combination of clinical signs culminates in an animal that appears to “waste away,” coining the name of the disease.

“Chronic wasting disease is of concern for wildlife managers and deer breeders alike,” said Terry Hensley, DVM, TVMDL’s assistant agency director and veterinarian with the Texas A&M AgriLife Extension Service. “This disease presents a challenge for anyone tasked with managing our deer resources in Texas.”

In 2012, CWD was first discovered in Texas in free-ranging mule deer in the Hueco Mountains. Since then, the disease has continued to be detected in the West Texas and Panhandle regions in mule deer, white-tailed deer and elk.

Texas’ history of CWD has been recent, compared to other states, and the diagnostic testing continues to increase as state agencies attempt to control the disease. In Texas, TVMDL is the only laboratory approved to test for CWD.

Detecting the Disease

Once at the laboratory, TVMDL tests possible CWD samples through one of two methods: enzyme-linked immunosorbent assay, ELISA, which is performed postmortem, or immunohistochemistry, IHC, which can be performed postmortem or antemortem.

Under the recent emergency order, all deer from movement-qualified deer breeding facilities must undergo antemortem testing prior to being transferred to a release site. The antemortem test is performed on either a tonsil or rectal biopsy.

If a sample is suspect for CWD at TVMDL, it is sent to the National Veterinary Service Laboratory in Ames, Iowa, for confirmatory testing and a final diagnosis.

The TVMDL commitment to Texas

Although other laboratories across the U.S. offer CWD testing, TVMDL sets itself apart through its dedication to the individuals in the Texas deer industry. The agency works closely with other state agencies and deer breeders to establish working relationships and personal connections.

For more information about CWD testing at TVMDL, visit tvmdl.tamu.edu or call the Bryan-College Station laboratory at 1-888-646-5623.