Health officials are warning that a fatal disease currently impacting deer could jump species and infect humans. “We are having discussions right now with the CDC, [National Institutes of Health] and others about how they have to elevate the critical nature of this situation and make it clear that this is a very critical, time-sensitive public health issue,” said Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research & Prevention at an informational hearing before the House Environment and Natural Resources Finance Division of the Minnesota state legislature.
Chronic wasting disease, part of a family of prion diseases, affects deer, elk, reindeer, sika deer and moose. As of January, the CDC reported that CWD has been reported in 24 states in the U.S. and Canada. The infection impacts the animals’ brain, spinal cord and other tissues causing dramatic waste loss, stumbling, listlessness, and drooling among other symptoms. It is always fatal. There are no vaccinations, cures or treatments for the disease.
“It is my best professional judgment based on my public health experience and the risk of BSE transmission to humans in the 1980s and 1990s and my extensive review and evaluation of laboratory research studies … that it is probable that human cases of CWD associated with the consumption of contaminated meat will be documented in the years ahead. It is possible that number of human cases will be substantial and will not be isolated events,” continued Osterholm.
Prion diseases first captured the public’s imagination with the rise of “mad cow” disease – a slow degenerative virus that slowly “eats” a cow’s brain causing erratic behavior and eventually death. A cow imported from Canada in 2003 resulted in the loss of some foreign cattle markets for several years.
According to the USDA, only six cases of mad cow have been confirmed in the United States – the last being in August 2018 in a mixed breed cow in Florida. Prion diseases include mad cow disease or Bovine Spongiform Encephalopathy (BSE), Chronic Wasting Disaese (CWD), and in humans Creutzfeld-Jakob disease (CJD), Kuru, among others and can occur in both animals and humans.
Prion Diseases in Humans
Deaths from the Prion family of diseases have increased in the world population by 275 percent since 1979 from 179 to 492 in 2016. Cases of Creutzfeld-Jakob disease in humans are said to be caused by prions – normally occurring proteins that misfold and affect signaling processes, causing degeneration of the brain and eventual death. Most cases occur spontaneously from a mutation of the protein, from genetics, and a small number of cases from medical procedures, known as iatrogenic cases. Occurrence of the latter reached slightly over 500 cases from surgeries and human growth hormone. Thanks to increased recognition of infected persons in addition to improved sterilization methods, iatrogenic cases are rarely now seen.
Another form of prion disease, kuru, is contracted by cannibalism. The Fore people in Papua New Guinea experienced an epidemic of the fatal brain disease from a funeral ritual that involved eating human brains. Studies of the tribe found that those who did not contract the disease carried a genetic mutation called V127 that seemed to confer some protection against kuru.
Though cases are rarely transmitted through ingestion of infected tissue, the U.S. has taken extensive measures to ensure that infected tissue containing prions does not enter the U.S. food supply. According to the USDA, a system of strong interlocking safeguards protects human and animal health, and include the removal of specified risk materials (SRMs) – those tissues that may contain the BSE agent in an infected animal – from the human food chain.
The World Health Organization classifies a country’s Bovine Spongiform Encephalopathy, or BSE, status as “atypical” or “typical” – with “atypical” not changing a country’s BSE risk status because it can occur spontaneously in a herd.
For now, experts in Minnesota have asked for $1.8 million to fund more research into a test for the rapid detection of chronic wasting disease. Currently it take two weeks to detect the disease and requires confirmation.
Will a rapid test for humans follow? Check back in regularly at HSToday to find out.