Prion disease found in camels

Dromedary camels in northern Africa have a neurodegenerative prion disease that may have originated decades ago.

"Although it has not been possible to date back the first cases of illness, information gathered from breeders and slaughterhouse personnel suggests the illness has been present since the 1980s," according to an article in Emerging Infectious Diseases. The article, published online in April ahead of print in June (Emerg Infect Dis 2018;24:1029-1036), indicates researchers found the prion disease among dromedaries brought to one of Algeria's largest abattoirs, by volume, for cattle, camels, and small ruminants.

The report authors examined the brains of three camels with neurologic signs and a fourth without. They found spongiform changes and degeneration in brains of the three animals with clinical signs.

They also collected the lymph nodes from one of those with clinical signs and found disease-causing prion proteins in that tissue, the article states. Spread of prions through the lymph nodes, as with scrapie and chronic wasting disease, is associated with prion shedding.

Retrospective analysis showed about 70 dromedaries brought to the slaughter facility during 2015 and 2016—3 percent of the total—had neurologic signs consistent with the disease. The disease has been observed only in animals more than 8 years old, whereas camels tend to be slaughtered at younger than 5 years.

"In the past 5 years, neurologic symptoms have been observed more often in adult dromedaries at antemortem examination," the article states.

Clinical signs of the disease included weight loss, behavior abnormalities, and neurologic signs such as tremors, aggression, hyper-reactivity, gait changes, ataxia of hind limbs, falls, and difficulty rising. The disease kills dromedaries three to eight months after clinical signs begin.

The authors wrote that the prion disease may have originated in another species, but it has a biochemical signature distinct from those of bovine spongiform encephalopathy and scrapie, and neither disease has been found in Algeria. Further study of the disease's geographic distribution will help.

"Our identification of this prion disease in a geographically widespread livestock species requires urgent enforcement of surveillance and assessment of the potential risks to human and animal health," the article states.