Prion Safety and Hygiene

Prions are the least well known of microscopy pathogens. They were discovered only in the 1980s.

Diseases that are caused by prions generally affect animals, but a few strike humans: Fatal familial insomnia, Creutzfeldt-Jakob disease, Kuru, and most famously Creutzfeldt-Jakob disease, which is related to the bovine “Mad Cow Disease”. However, scientists suspect other common diseases may be caused by prions. The incubation period for these diseases can be decades - years after the prions enter the body, symptoms appear. And prions are such an unknown that they pose a risk.

Prions are still a mystery to some extent, more than 30 years after their discovery. They can be pathogens and cause disease but how infectious they are (how many prions does a person need to get in his body to cause the disease), how hardy they are, and what can destroy or disable them are not known. Like viruses, prions are not really alive, so it is incorrect to say they can be killed. For viruses, we say they are disabled or destroyed. Similar language would be appropriate for prions. Except that we know that autoclave temperatures (250 F) can destroy viruses and we know viruses contain genetic information in DNA. We don’t know what temperatures are needed to destroy prions, and we know they are not as chemically complex as DNA.

Further, fast tests are not readily available to determine if a surface has prions on it. Although scientists can identify prions on surfaces, it is not easy and the technology and knowledge for identifying them has not spread to most medical facilities.

This poses uncertainty for the industrial hygienist and infection control officer.

What the waste management professional needs to know about prion safety

If you know prions are present, be very careful and consider calling in a microbiologist for help.

Conventional sterilization techniques should not be assumed to destroy prions. These include both chemical antimicrobials and autoclave-temperature heat. Incineration temperatures will almost certainly destroy prions with enough residence time, but you will have trouble validating that no active prions survive and it is so difficult to identify the presence of prions that trying to destroy them through incineration seems pointless.

The University of Minnesota recommends incineration for non-tissue solid waste produced at their labs that is suspected to contain prions. For liquid waste, they recommend treatment with sodium hydroxide followed by disposal to the drain or in a hazardous waste pickup. Michigan State University also mentions bleach treatment for liquid waste Note that these academic researchers are generally working with prions known to cause diseases in animals, not humans. Disposal of animal carcasses is done by alkaline hydrolysis, even if they have been infected with prions.

Virginia’s Department of WIldlife Resources cautions hunterss about touching animal bodies that may have prions.