A team of scientists led by Cornell University has recently confirmed the first cases of canine distemper virus (CDV) in tigers and leopards in Nepal. This virus, usually affecting dogs, can cause fatal neurological diseases and thus be a significant threat to already dwindling big cat populations.
“Canine distemper virus has been repeatedly identified as a threat to wild carnivores and their conservation,” said study senior author Martin Gilbert, a wild carnivore health specialist at Cornell. “This study is a first step to understanding the potential impact for Nepalese tiger and leopard populations.”
Although scientists have already suspected that CDV can infect big cats, this is the first definitive proof of infection in Nepal. The experts found that 11 percent of tigers (three out of 28) and 30 percent of leopards (six out of 20) had antibodies to this virus, indicating that they had been infected in the past.
While relatively little is known about Nepal’s leopards, studies suggest that their population is in decline due to a mixture of poaching, habitat loss, and human-wildlife conflicts. Moreover, they are also facing increasing competition caused by the expansion of the country’s tiger population, which has tripled over the past 12 years (although, globally, this species remains endangered too).
As the larger and stronger species, tigers are frequently displacing leopards from national parks into areas with more people, where they often prey on street dogs. According to the researchers, these dogs may be the source of infection. “We already know CDV is circulating in the Nepali dog population and that leopards frequently eat dogs, while tigers do not,” said study co-author Jessica Bodgener, a veterinarian at Wildlife Vets International.
“When we found a greater exposure in leopards it seemed like a good fit, but we need more evidence to be sure. And we can’t forget three tigers also tested positive. If tigers aren’t eating dogs, it raises the question, how did these animals get infected? The situation may not be straightforward.” Other species, such as jackals or civets, could also act as reservoirs.
The scientists recommend several immediate actions to control the spread of the virus, including: raising awareness of wildlife managers, expanding molecular testing and genetic sequencing of leopards and tigers, continuing to monitor the presence of antibodies, vaccinating dogs and potentially the big cats themselves, and – since small, isolated populations are most at risk of CDV outbreaks – increasing habitat connectivity through wildlife corridors.
“Since 2014, we have seen ten leopards showing neurological disease that could be consistent with CDV infection. With increased awareness, we plan to confirm future cases and obtain genetic sequences to help determine the source of infections,” concluded co-author Amir Sadaula, a veterinarian at the National Trust for Nature Conservation (NTNC).
The study is published in the journal Pathogens.
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