October 11, 2002 Budgeteer News by Pat Faherty
The most imaginative Hollywood horror movies have nothing on the prion.
The microscopic protein based particles are blamed for a family of incurable deadly diseases that in different forms infect various animals and people.
The most currently discussed is chronic wasting disease, which affects deer and elk and has been found in Minnesota and Wisconsin.
While that alone puts prions in the “dreaded” category, they are also tough, versatile and still somewhat mysterious.
Antibiotics don’t deter them. They are very heat resistant, freezing doesn’t phase them, they’re infectious and partially resistant to digestion.
Prions are invulnerable to irradiation, dehydration and many chemical disinfectants. They have survived acid and fermentation and proved much harder to diagnose than viruses or bacteria.
Prions can cling to plastic and metal like glue and don’t seem to mind hanging around, remaining potent for years.
“They’re a very sticky substance,” said Dr. Louise Hawley, assistant professor of medical microbiology at the UMD School of Medicine.
Researchers believe prions are mutant protein forms of normal molecules found in all mammals. And they somehow have the unique ability to convert their fellow molecules into more mutants while taking on the form of their host.
“If you infect a deer with material from an elk, it ends up as deer prions,” she said. “So you can’t tell what the source of the prions was.”
Prions are blamed for the Transmissible Spongiform Encephalopathies (TSE), fatal brain ailments such as mad cow disease, Creutzfeldt-Jakob disease (CJD) in humans and CWD.
Mad cow disease put prions on the map, and research has raised red flags on handling prion tainted tissue, blood and cadavers.
“We don’t do biopsies anymore for CJD because of the contamination issue,” said Dr. Rebecca Meyerson, a neurology specialist with St. Mary’s/Duluth Clinic.
Meyerson and Hawley joined Dr. Glen Del Giudice, a scientist with the Minnesota DNR, for public forum on prions and CWD.
Unlike most hunter focused CWD sessions, the UMD sponsored program took a broader approach highlighting the medical and biological aspects.
Del Giudice made the point and was reinforced by Meyerson that no evidence has linked CWD to human health.
They also discussed the “species barrier,” which some researchers believe helps contain diseases.
Del Giudice used the example of predators as evidence of this barrier.
“If it (CWD) were to jump species you would see it in wolves or bears,” he said. “A carnivore would be at risk. They consume everything.”
“We do have a species barrier, and species barriers are difficult to get through,” said Hawley. “But once it gets in, it’s bad.”
As an example, she is concerned about big cats at the zoo that are fed a lot of road-kill.
The unpredictability of prions prompted the Medical Society of Milwaukee to come out on the side of caution regarding venison this week.
It wants Wisconsin to consider taking the same precautions imposed on the British beef industry, on the currently unregulated “custom processing industry” of deer carcasses.
The measures would control what deer parts can’t go in sausage and carcass disposal.
The society also voiced concern about allowing licensed Wisconsin beef processors exemptions to butcher deer.
“Deer prions could survive standard cleaning procedures imposing a potential risk to the beef, pork and chicken subsequently processed,” said the position paper.
The society cited the uncertainty with how CWD may behave. It said some studies suggest that deer prions from CWD can convert human prions into infectious mutants.