Has prion disease in wildlife jumped the species barrier to humans?
The outbreak of mad cow disease in Great Britain cattle in shocked the world. The first sick cow was identified in 1984. By 1992-1993, 100,00 cases were identified.Over 4 million head of cattle were slaughtered to stop the spread.
The disease persisted and in 1994 people fell ill with neurological symptoms that progressed from lack of coordination to dementia, being bedridden, and death. The next year, the first human death, a 19 year-old-man occurred. The disease was linked to eating infected meat. It not only spread to humans, pet cats and zoo animals died.
Authorities had assured the people that eating beef was safe because a similar prion disease in sheep called scrapie did not result in human disease if consumed. Researchers found the cause of the infected beef was because animal feed had been supplement with contaminated protein slurry from rendering plants where carcasses of sick animals were taken.
As a physician, my interest in infectious diseases resulted in researching prion disease over years. It is not caused by a virus or a bacterium, it results from an abnormal protein called a prion that becomes infectious when its molecular structure changes. There are a number of prion diseases, some are infectious like mad cow, others are inherited disorders. They vary in duration of illness and symptoms, but all are fatal. There is no treatment.
Chronic Wasting Disease in deer was first identified a Colorado research center in 1967 after exposure to scrapie infected sheep. I worried it could spread to humans from infected venison like the bovine disease had in Great Britain.
In a Canadian study on primates fed CWD infected venison, the monkeys died. The close genetic relationship to humans made it likely it could infect humans. There is a species barrier but the protection is incomplete. There are forms of prion disease in many mammals including sheep, mink and mice.
This month, a report in the journal of Neurology stated two hunters died in 2022 from a rapidly progressive form of prion disease. It appears to be transmission of CWD to humans from eating infected venison.
My medical thriller Fatal Feast explores a story line using this concept. I will share my author note from the publication in 2019 below:
AUTHOR NOTE
Fatal Feast is fiction, but prions are real and universally fatal. Prions are abnormally twisted proteins that recruit normal proteins to change conformation and clump, damaging the body. In the diseased state, the abnormal proteins are found throughout body fluids and in muscle, but the nervous system and the brain are most affected.
Prion disease is easily transmissible via surfaces contaminated by contact with infected body fluids and tissues. These deadly, infectious proteins kill people in the United States today as they did in Great Britain in the 1990s. Patients have died from blood transfusions, contaminated neurosurgical instruments, and tissue transplants. Some forms of prion disease are inherited.
The fascinating history of the discovery and consequences of abnormal prions can be found in many sources. The most recent outbreak occurred in the United Kingdom killing more than two-hundred people who contracted the deadly disease by eating beef from infected cattle. Prion disease spread by consuming the bovine sources is called variant Creutzfeldt-Jakob disease or vCJD. Millions of cows were euthanized and incinerated to stop the spread, but shipments of infected meat products spread the disease to other countries during the U.K. epidemic. Initially, this outbreak was concealed by authorities until it could no longer be hidden from the public.
Betty Kuffel
Author Betty Kuffel, MD 