Canine distemper, a viral disease that's been infecting the famed lions of Tanzania's Serengeti National Park, appears to be spread by multiple animal species, according to a study published by a transcontinental team of scientists. Writing in the journal Proceedings of the National Academy of Sciences, they say domestic dogs are no longer the primary source of the disease's transmission to lions and that wild carnivores may contribute as well.
Their findings demonstrate that in natural ecosystems, a deadly virus can jump between species and thrive, thereby threatening vulnerable animal populations.
"Our study shows that the dynamics of canine distemper virus are extremely complex, and a broadened approach - focusing not only on domestic dogs--is required if we are to control the disease among lions and other wild animal species," said veterinary researcher Felix Lankester of Washington State University's Paul G. Allen School for Global Animal Health, a co-author based in Tanzania.
In 1994, a mysterious neurological ailment wiped out 30-percent of the lion population in the Serengeti, one of the largest wildlife regions in the world. Scientists determined it was canine distemper, a disease previously thought to infect only dogs, coyotes and a small number of other mammals. Evidence suggested the lions had contracted the virus from dogs living in villages and settlements nearby. A domestic dog vaccination campaign was launched to curb the infection's spread. It worked--among dogs, at least.
After analyzing three decades of blood serum data collected from lions and domestic dogs, the study's researchers discovered that the virus continues to circulate in the lion population while significantly declining among dogs.
The dog's role in spreading the disease appears to be shrinking, conclude the paper's authors, an international team of veterinarians, disease ecologists, epidemiologists and mathematical biologists.
"Domestic dog populations immediately surrounding the Serengeti National Park are not the sole driver of canine distemper infections in lions, and its persistence is likely to involve a larger multi-host community," they write.
Other species, including hyenas and jackals, are probably transmitting the disease and keeping it looming in the wild, they say. Consequently, outbreaks among lions and other already-threatened animals could occur at any time.
Researchers say more work is necessary to identify which species spread distemper and what triggers the spillovers. For example, it's believed that an infected hyena or other carnivore feeding on a carcass can disperse the virus through mucus secretions to other predators at the same site.
A better understanding of canine distemper virus and its dynamics in the wild is necessary to effectively monitor and better control the disease among lions and other threatened animals, the scientists report.
Proceedings of the National Academy of Sciences