Researchers developing new live-animal test for CWD

A team of researchers led by Nicholas Haley, DVM, PhD, at Kansas State University, have made significant progress in developing a new live-animal test for chronic wasting disease, or CWD. In recent years, CWD, which affects cervids such as deer and elk, has spread to herds in 23 states. CWD is classified as a transmissible spongiform encephalopathy, similar to BSE in cattle. The disease has not, however, ever been shown to affect cattle or to pose a food-safety risk in venison.

In several cases, CWD has turned up in captive deer farms or “high-fence” deer-hunting operations, leading to concerns that interstate transportation of deer for breeding purposes in those operations could contribute to introduction of the disease to new areas. A fast and effective test on live animals could help address those concerns and allow more efficient surveillance in some wild herds.

Haley and his team, working with USDA researchers in Ames, Iowa, Penn State University and a deer farm in Pennsylvania, have been working to evaluate the sensitivity of the real-time quaking-induced conversion (RT-QuIC) assay by using recto-anal mucosa-associated lymphoid tissue (RAMALT) biopsy specimens and nasal brush samples collected from 409 live farmed white-tailed dee.

They compared results of the RT-QuIC assay with immunohistochemistry (IHC) analysis in antemortem and postmortem testing of RAMALT, brainstem and medial retropharyngeal lymph node samples. They describe IHC as the current gold standard for such testing.

The researchers report their results show RAMALT testing using RT-QuIC assay had the highest sensitivity, at 69.8%, compared to that for postmortem testing, with a specificity of greater than 93.9%. The data, they conclude, suggest that RT-QuIC, like IHC analysis, is an effective assay for detection of CWD in rectal biopsy specimens and other antemortem samples. With further research to identify more sensitive tissues, bodily fluids, or experimental conditions, the method has potential for large-scale and rapid automated testing for CWD diagnosis.

Results of the study, titled “Antemortem Detection of Chronic Wasting Disease Prions in Nasal Brush Collections and Rectal Biopsy Specimens from White-Tailed Deer by Real-Time Quaking-Induced Conversion,” are published in the Journal of Clinical Microbiology.