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Bleach inactivates infectious disease found in deer

Researchers have found a way to inactivate the prions that cause chronic wasting disease in deer, elk, and moose on surfaces like hunting knives. gjohnstonphoto / iStock / Getty Images Plus

Chronic wasting disease (CWD) is a fatal illness that can affect deer, elk, and moose. The disease attacks the animal’s brain, causing weight loss and abnormal behavior in later stages. It is caused by misfolded proteins called prions. Prions cause a range of diseases across species, including bovine spongiform encephalopathy (or “mad cow disease”), scrapie in sheep, and Creutzfeldt-Jakob disease in people.

So far, CWD has been detected in animals in 26 U.S. states and three Canadian provinces, as well as in Norway, Finland, and South Korea. There are no confirmed cases of CWD being transmitted to humans, but other prion diseases have been shown to infect people.

Animals with CWD have a buildup of prions in their bodies—especially their brains. These infectious prions stick to stainless steel surfaces like hunting knives and are particularly hard to inactivate. Current methods are either hazardous, costly, or not commonly available. Previous studies found that bleach can be an effective decontaminant for other prion diseases.

A team of NIH researchers led by Dr. Brent Race set out to determine whether bleach could inactivate CWD prions. The study was funded by NIH’s National Institute of Allergy and Infectious Diseases (NIAID). Results appeared in PLOS One on October 4, 2019.

The researchers first worked with CWD-infected brains from white-tailed deer. Samples were ground and treated with various concentrations of bleach or water for 1 or 5 minutes. They were then immediately diluted to prevent further action of the bleach. Treatment with 10% bleach or higher eliminated all prion seeding, even after only one minute.

The team then coated stainless-steel wire with high levels of CWD prions from the brains of infected white-tailed deer and mule deer. These wires were chosen to model the stainless-steel knives and saws used by hunters and meat processors. The wires were dried and then treated with 1%, 10% or 40% concentrations of bleach for either 1 or 5 minutes.

A 5-minute soak in a 40% solution of household bleach decontaminated even the most infected stainless-steel wires. The researchers note that their test recreates a worst-case scenario situation for CWD prion contamination. The tissues most frequently handled when preparing a deer—muscle, skin, and connective tissues—all have much lower levels of infectious prions than the brain and spinal cord.

Bleach couldn’t effectively decontaminate solid brain tissue from infected animals. The researchers note that this isn’t surprising, as bleach is used as a surface decontaminant and fails to penetrate tissues. This highlights the importance of thoroughly cleaning and removing solid pieces of tissue before decontaminating surfaces with bleach.

“As the range and number of deer, elk, and moose infected with chronic wasting disease expands, so does the potential for human exposure,” Race says. “While no human cases of CWD have been confirmed to date, it remains prudent to handle CWD-infected tissues with caution. Here we demonstrate that bleach treatment can serve as an easy and practical method for disinfecting equipment contaminated with CWD prions.”

—by Erin Bryant