Fire may help control chronic wasting disease

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The prion proteins that cause chronic wasting disease survive for years in soil and are taken up by plants.

Dr. Mark Zabel, associate director of the Prion Research Center at Colorado State University, thinks controlled burns may help.

"I do think that it's one of the only realistic and viable, possible solutions to the problem of CWD," he said. "It's still spreading at a tremendous rate, and it's now endemic in about half of the lower 48 states, and so our options are becoming very limited."

CWD is a neurologic disease, and it is always fatal to infected cervids, including deer, elk, and moose. It spreads animal to animal and through their environments, and its spread has raised concerns that the disease could cause local extinctions (see JAVMA, Aug. 15, 2017).

The prions are hardy, like spores or bacteria, and they are spread over substantial wilderness areas, Dr. Zabel said.

His research plan would take advantage of controlled burns already scheduled in national parks in Colorado and Arkansas, where the National Park Service is planning the fires for wildfire control and habitat restoration—management unrelated to CWD. Dr. Zabel has been modeling, in laboratory conditions, fire temperatures and durations and the effects those fires could have on prion titers.

The pilot study he wants to conduct would involve measuring amounts of CWD-causing prions found in soil and plants before the fires, and amounts in soil and new plants that grow afterward. The fires would affect herd movements, he said, but deer would be expected to return without any long-term changes in migration or habitat.

Dr. Zabel said he has heard concerns that controlled burns could push infected cervids into new areas, which he said is a possibility, and that could be measured through surveillance and disease prevalence estimates in areas around controlled burns.

Dr. Zabel said CWD is an enormous problem, and many large-scale solutions are worth considering. One recent suggestion led him to deliberate whether introducing wild horses to the Rocky Mountain ranges could interrupt CWD transmission since horses are resistant to prion disease and their grazing could remove some contaminated forage.

"This is such a hard thing to get ahold of because of the sheer geographical area that we're talking about and the persistence of prions in the environment," he said.

For now, he said, spread of the disease shows no signs of slowing.