Italian
and Algerian researchers released new evidence of prion disease in
three dromedary camels found in an Algerian slaughterhouse, according to
a new study in Emerging Infectious Diseases.
The
discovery, now being called camel prion disease (CPD), has raised more
questions than answers about this deadly illness characterized by
misfolded brain proteins.
"These camels are quite intriguing,"
prion expert Valerie Sim, MD, associate professor at the University of
Alberta, told CIDRAP News. "If we know anything about prions it's that
they can they can cross species; it's not easy to do, but they can. So
it's very concerning if you have any infected animals in the food supply
chain."
Sim was not involved in the new study.
In prion
disease, the normal shape of a protein is contorted, and that triggers a
domino-like effect in neighboring proteins, leading to fatal and severe
neurodegenerative disease. Prion diseases can affect both humans and
animals, and though inter-species transmission is rare, it can happen,
as it did most famously during the bovine spongiform encephalopathy
(BSE, or "mad cow") epidemic, which started in the late 1980s in the
United Kingdom.
In both humans and animals, the diseases can
happen spontaneously, or they can be inherited from a genetic mutation
or, rarely, transmitted when a person eats the meat of an infected
animal. The last category, infectious prion disease, is the most
concerning for researchers working on the human-animal interface.
New threat in animals
"Is
there a clear exposure risk in camels? That's what's needed to be
understood," said Sim. She said that the presence of prions in the
camels' lymph tissues suggests the disease was acquired and not
spontaneous, likely from something the animal was digesting.
In the Emerging Infectious Diseases study,
researchers describe CPD in three symptomatic camels from a Saharan
population in southeastern Algeria, where the animals were brought for
slaughter to the Ouargla abattoir in 2015 and 2016. Dromedary camels are
commonly slaughtered and consumed in many parts of North Africa and the
Middle East.
Breeders bringing the camels to slaughter noted
several neurologic symptoms from 2010 to 2015 in about 3% of their
animals, including "weight loss; behavioral abnormalities; and
neurologic signs, such as tremors, aggressiveness, hyperreactivity,
typical down and upward movements of the head, hesitant and uncertain
gait, ataxia of the hind limbs, occasional falls, and difficultly
getting up." Anecdotal evidence collected from employees at the
slaughterhouse suggests that these symptoms have been present since the
1980s.
The researchers, from Algeria and Rome, took brain samples
as well as samples from the cervical, prescapular, and lumbar aortic
lymph nodes from three symptomatic and one healthy camel. They confirmed
the diagnosis by the presence of disease-specific prion protein in
brain tissues from the symptomatic animals. The authors said the
presence of prions in the lymph nodes suggests infection, but the
disease remains a mystery.
Disease origin unknown
"The
origin of CPD is unknown. It might be a disease unique to dromedaries or
a malady deriving from transmission of a prion disease from another
species," the authors concluded. They noted, however, that BSE from
imported meat in the late 1980s cannot be ruled out.
Michael
Osterholm, PhD, MPH, director of the University of Minnesota's Center
for Infectious Disease Research and Policy, publisher of CIDRAP News,
said the study was noteworthy especially as it comes on the heels of new
information from Canadian researchers that showed that chronic wasting
disease—another prion disease—in deer and their relatives can be
transmitted to non-human primates fed meat from infected animals.
"The
whole issue of prions and meat consumption is a new and much more
serious topic we need to look at," Osterholm said. "Even though there's
no evidence that there is transmission [from camels], the absence of
evidence is not evidence of absence."
See also:
Apr 16 Emerg Infect Dis https://wwwnc.cdc.gov/eid/article/24/6/17-2007_article" rel="nofollow - study
Soirce: http://www.cidrap.umn.edu/news-perspective/2018/04/mad-camel-disease-new-prion-infection-causes-alarm" rel="nofollow - http://www.cidrap.umn.edu/news-perspective/2018/04/mad-camel-disease-new-prion-infection-causes-alarm