Now Dogs Threaten Big Cats

Canine distemper alert sounded in tiger reserves, but leopards are more at risk

Tehelka, 23 June, 2013

Citing reports of the spread of the canine distemper virus (CDV) in wild tigers of the Russian Federation and Indonesia, on 14 June, the National Tiger Conservation Authority (NTCA) has asked India’s tiger states to vaccinate stray dogs around tigerreserves and observe wild animals for any abnormal behaviour.

Canine distemper, the NTCA letter noted, is “incurable, causing high fever… progressing to seizure, paralysis and death”. Infected animals lose fear, show disorientation and are often unable to hunt. On 10 June, the BBC reported, quoting John Lewis, director of Wildlife Vets International, that CDV might have already spread among the critically-endangered Sumatran tigers.

The symptoms of CDV were first recorded in wild tigers nearly a decade ago in the Russian Far East, where the big cats routinely hunt village dogs. I recall a detailed account by A Rybin, an official with the Wildlife Conservation Society- Russia, who darted a young male tiger that behaved like “the family pussycat” in February 2010.

Photo courtesy: P Fomenko/WWF

“This animal neither ran away or towards people, as if people long ago failed to interest him… The previous day, the tiger had killed and eaten two dogs. Now, apparently satiated, he was leisurely strolling around between the houses and cars parked nearby (see photo). He seemed completely calm… but appeared very interested in cars. He followed them, smelled them, and rubbed his cheeks on their bumpers… Unlike most tigers, who normally whirl in anger with impressive growls upon getting darted with a needle, this tiger… didn’t charge in our direction, didn’t roar, but merely hopped up twice, like a rabbit,” recounted Rybin.

A century ago, canine distemper was reported as a disease that affected dogs. It was also responsible for wiping out the thylacine, or the Tasmanian tiger, by the 1930s. In the Serengeti-Mara landscape, CDV killed silver-backed jackals and bat-eared foxes in 1978 and wild dogs in 1991. By that time, the virus had evolved to target non-canid (dog) species as well.

In 1992, a CDV outbreak killed 17 big cats — lions, tigers, leopards and a jaguar — at the Wildlife Waystation facility in California. Though Serengeti lions were exposed to the virus since 1981 without showing any signs of canine distemper, an epidemic in 1994 killed nearly one-third of Tanzania’s second biggest lion population. The outbreak soon spread to Kenya’s Maasai Mara, infecting hyaenas and leopards. In 2000, the virus killed thousands of seals in the Caspian Sea.

These instances, and numerous other cases of CDV fatalities in big cats in zoos across the world, demand that the threat to wild tiger populations should not be treated lightly. Given the rapid fragmentation of their habitat, tigers are increasingly preying on livestock and dogs in many parts of India. But leopards are probably many times more exposed to the threats of rabies and CDV contamination.

Compared to tigers, leopards use human landscapes more frequently and intensely. In many areas, dogs are their most preferred prey. An analyses of leopard droppings in Mumbai’s Sanjay Gandhi National Park (SGNP), for example, has shown that dogs account for 60 percent of their diet. Yet, the standard post-mortem investigation of wild cats is limited to checking for external injuries and visceral examination.

“Rabies and CD viruses can spread from domestic and feral dogs to wild cats, particularly when a population is significantly dependent on such a prey base like the leopards of the SGNP are,” says researcher Krishna Tiwari who has been studying Mumbai’s leopards for many years. “It will certainly be useful if we have some data on these infections.”

It may not be feasible to conduct antigen-antibody tests for CDV on every big cat immobilised for radio-collaring. But as the prompt NTCA directive advises, every post-mortem must involve collection of brain tissues for pathology tests in labs. The results may also tell us if certain unnatural conducts of the so-called conflict animals are actually symptoms of affected central nervous system.