A fatal, Alzheimer's-like disease that attacks cheetahs' internal organs and has impeded breeding of the cats in captivity may be spread by their feces. Researchers from Japan and China report in the journal Proceedings of the National Academy of Sciences USA that the disease, AA amyloidosis, was transmitted to mice exposed to fecal proteins from a cheetah that died of it.
The cheetah is classified as an endangered species. Only 12,000 to 15,000 are believed to remain in about 25 countries, down from 100,000 in 44 countries in 1900, according to the Cheetah Conservation Fund. Breeders would like to have a self-sustaining population of cheetahs in captivity, but in North America only 20 percent of captive cheetahs reproduce, and only 75 to 80 percent of cubs survive to reproductive age, says Adrienne Crosier, a reproductive biologist at the National Zoo in Washington, D.C.
Thanks to inbreeding, cheetahs have greater susceptibility to diseases such as AA amyloidosis, which is among a group of disorders characterized by the accumulation tangles of misfolded protein called amyloid fibrils. Other diseases in the group include Alzheimer's and type 2 diabetes in humans as well as the prion (infectious protein) diseases such as scrapie in sheep, bovine spongiform encephalopathy (aka mad cow disease) and chronic wasting disease in deer and elk. In cheetahs amyloid fibrils build up in the spleen and liver, typically following an inflammatory stomach disease.
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Researchers had found that amyloid-laden tissues from dead cheetahs could transmit the disease to mice, but they didn't know whether cheetahs might be passing amyloid amongst themselves. The Japanese and Chinese group injected mice with amyloid extracted either from the liver or the feces of a male cheetah that died at age four from the disease. (The normal captive cheetah life span is eight to 12 years.) The fecal protein was found to be more likely to transmit the disease to the mice, and protein taken from the feces of three other cheetahs also spread the disease.
The researchers say the fecal protein could linger in soil and be picked up by the cats' fur, causing it to spread during mutual grooming. They add that determining the way the disease is transmitted is key in preventing its spread.