EDMONTON - Canadian health officials have confirmed the country’s
second-ever case of variant Creutzfeldt-Jakob disease, the rare
human form of the so-called “mad cow disease” usually caused by
eating infected beef.
The head of the federal agency that monitors the disease says the
man, an Ontario resident, is believed to have been infected in
Saudi Arabia, and that the chance he was infected by eating
Canadian beef is “just about zero.”
“It’s so low so as not to be a concern for the safety of Canadian
beef,” said Dr. Michael Coulthart, director of the Canadian
Creutzfeldt-Jakob disease surveillance system at the national
microbiology lab in Winnipeg.
Variant Creutzfeldt-Jakob disease is the human form of bovine
spongiform encephalopathy, or BSE. It is most commonly caused by
eating meat from BSE-infected cows, though there have also been
documented transmissions through blood transfusions and the
potential for infection through medical and dental tools.
Only one other person in Canada has been confirmed to have had the
human form of mad cow disease, a Saskatchewan man who died in
2002.
Information released by Health Canada in both Arabic and English
says the Ontario man began experiencing symptoms just prior to
immigrating to Canada from Saudi Arabia in 2010. Health Canada
says there is no indication the man ever donated blood or received
a blood transfusion in Canada, or underwent any surgical
procedures outside the government’s infection control guidelines.
The statement says the risk to the Canadian blood supply is
considered to be “very low.”
Despite a relatively small number of human deaths, the emergence
of mad cow disease in animals and humans in the 1980s and 1990s
had a huge impact around the world, prompting the large scale
culling of animal herds, leading to massive changes in animal
feeding guidelines, and devastating cattle operations and trade
globally.
Canada’s cattle herd was believed to be BSE-free until May 2003,
when the first case of mad-cow disease was confirmed in a dairy
cow on a farm in northern Alberta.
The discovery led to strict bans on the import of Canadian beef
and cattle in the United States, rocking Alberta’s agricultural
industry.
Outbreaks of the human form of the disease also led to changes in
blood donor regulations in a number of countries, including
Canada.
The discovery of a new case of variant Creutzfeldt-Jakob in Canada
last month prompted an almost immediate change in the country’s
blood donation policies, which now restrict anyone who was in
Saudi Arabia for six months or longer in the period from 1980
to1996 from giving blood. The restriction previously related only
to the United Kingdom, France and Western Europe.
The disease first emerged in humans in the mid-1990s and peaked in
2000 in the U.K, where it has been the most prevalent.
Coulthart says the discovery of a new case in Canada remains
significant.
“It’s one of those cases where long-term vigilance is going to be
required to definitively deal with the issue ...,” he said. “Every
case is potentially significant, and you don’t want to miss any.
Any individual case can have large implications, potentially, and
you want to know as much as you can about the origins of each case
that does occur, whenever it occurs. So, that’s one reason to stay
vigilant.”
Because of the disease’s long incubation period, Coulthart says
there are also concerns about the “carrier effect,” where people
could have the disease for years — even decades — without knowing
it, then pass it on through blood transfusions or medical or
dental tools.
In that scenario, he says there could be a resurgence in the human
form of the disease in the future, particularly given that the
prion agent of the disease is extremely resistant to normal
methods of decontamination and disinfection.
One pathologist who studied the disease in Saskatoon in the 1990s
described it at the time as being “like something out of the
X-Files, the indestructible thing from outer space.”
According to the World Health Organization, the human form of mad
cow disease is an aggressive condition that begins with
psychiatric symptoms and dementia, and progresses quickly to
complete lack of physical control, leaving the person unable to
move or speak. The WHO says the disease leaves “daisy-like” holes
in the brain.