by Linda Weiford, WSU News
70-percent of all infectious diseases originate in animals. Changes in the environment and global travel contribute to their spread.
We are all connected.
Why are the famed lions of Tanzania’s Serengeti National Park being infected by canine distemper? An international team of scientists set out to answer that question in a study published in the Feb. 3 issue of the journal Proceedings of the National Academy of Sciences. The authors, including Felix Lankester of the Paul G. Allen School for Global Animal Health, conclude that the disease appears to be spread by multiple animal species.
Domestic dogs are no longer the primary source of the virus's transmission to lions, they write, with wild carnivores such as hyenas and jackals likely transmitting the virus as well.
"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," explained Lankester.
Dogs and beyond
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 revealed the lions had contracted distemper from dogs living in nearby villages and settlements. 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.
Veterinary researcher Felix Lankester administers a combined distemper/rabies vaccine to an owner’s dog in Tanzania.The dog's role in spreading the disease appears to be shrinking, conclude the paper's researchers, a collaboration of veterinarians, disease ecologists, epidemiologists and mathematical biologists.
Other species are probably transmitting the disease and keeping it looming in the wild, the authors say. Consequently, outbreaks among lions and other already-threatened animals could occur at any time.
"A better understanding of canine distemper virus and its dynamics in the wild is necessary to better monitor and control the disease among lions and other threatened animals," said Lankester of the Allen School.