India is scrambling to protect its beleaguered tiger population after several big cats tested positive for a virus common among dogs but deadly to other carnivores.
In the past year canine distemper virus has killed at least four tigers and several other animals across northern and eastern India, according to Rajesh Gopal, of the government's National Tiger Conservation Authority. He said tests for the virus would be carried out on every tiger carcass, and officials were considering a campaign to vaccinate dogs against canine distemper.
"We cannot vaccinate every dog, of course. But even 50% of dogs in the zones around sanctuaries would help," Gopal said. He did not give details of the plans being considered. There is no vaccine for big cats.
Dr AK Sharma, head scientist at the Indian Veterinary Research Institute, which performed the canine distemper lab tests, said: "These are very disturbing finds. The cases were quite distant from each other, and the latest was an area where there are no dogs. So it appears the virus is spreading." Since two cubs tested positive in a zoo in Patna, the Bihar state capital, Sharma and his colleagues have found at least four more cases: a red panda in the north-east state of Manipur, a wild tiger in West Bengal, a zoo lion in Darjeeling and, last month, a wild tiger in the Dudhwa tiger reserve in Uttar Pradesh.
"In the last case, forest guards said they saw the animal in a confused state before it died," he said.
Experts said there were probably more undetected cases, since testing for canine distemper has not been routine and few animals that die in the wild are ever found.
Canine distemper virus, a close relative of measles, is associated mostly with domestic dogs, though it has infected and ravaged other carnivore populations. It brought the US black-footed ferret to the brink of extinction in the late 1970s. In Tanzania in 1994, an epidemic probably introduced by tourists' dogs wiped out at least a third of the 3,000-strong African lion population in Serengeti national park.
While dogs can often recover from the disease, other animals including tigers, lions and leopards suffer fever, seizures and delirium before they die. There is no known cure.
Some experts said it was pointless to try to limit the disease, given how closely millions of Indians live alongside wildlife. Instead, the government should focus on other, proven threats such as poaching, prey loss to hunting and human encroachment into forests.
"Thinking we can control this is totally unrealistic. We have to live with it now, and assess whether it's really serious yet," said Ullas Karanth, the Bangalore-based Asian science director of Wildlife Conservation Society. "What South Africa has done, quarantining huge areas and creating disease-free spaces in the wild, is not feasible here."
India is home to more than half of the world's estimated 3,200 tigers. Despite dozens of tiger reserves in place, their numbers have sunk from an estimated 5,000-7,000 in the 1990s, when their habitat was more than twice as large.
Illegal poaching continues, with tiger parts fetching high prices on the black market because of demand driven by traditional Chinese medicine practitioners. Meanwhile, deforestation and urban growth bring the cats ever closer to human settlements and into conflict with villagers who will hunt any wild animals near their communities or livestock.