A lion enjoys a meat ice cream on a day called "Wild Freshness" at the zoo in Medellin, Colombia, February 26, 2017. REUTERS/Fredy Builes - RTS10GZK (Reuters)

Infectious outbreaks threaten the last Asiatic lions

Parasites and dog disease in India sweep through the cats’ only home, triggering fears for the species’ survival


Jaideep Hardikar
December 15, 2018 12:30AM (UTC)
This article was originally published by Scientific American.
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When two lion cubs were found dead one day this September in India’s Gir National Park, forest officials shrugged off their demise as “natural.” Three weeks later, however, 23 lions had perished — sparking fears an epidemic could very quickly devastate the last surviving population of the Asiatic lion.

Suspecting a viral outbreak, authorities captured the 19 remaining lions in the eastern edge of the sanctuary — the part where seven of the deaths had occurred — and isolated them individually at a care center. Only three survived.

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The canine distemper virus (CVD) was initially blamed as the main cause of the deaths, but experts caution other factors were probably involved. “We need a serious multidisciplinary investigation of the outbreak,” says wildlife biologist Ravi Chellam. The deaths have sparked debate not only over their immediate cause but also about conservation strategies — and have reignited a decades-old call for some members of the endangered lion species to be transferred elsewhere as insurance against future calamities. Wildlife scientists say an alternative home is key to long-term conservation of the species.

As a further precaution after the recent deaths, 33 lions from an adjoining forest range in Gir were also captured and quarantined; when they will be released back into the wild remains uncertain. And although forest officials asserted the epidemic had been contained, at least eight more lion corpses turned up in different parts of Gir since October, raising the recent toll to 31. (No cause has yet been confirmed for the latest eight deaths.)

What we know

All known remaining members of the species Panthera Leo persica — the Asiatic lion — are confined to Gir’s 1,880 square kilometers and roughly 18,000 square kilometers of human-dominated landscapes surrounding the sanctuary in the Indian state of Gujarat. The population rebounded from a mere 20 in 1913 to an estimated 600 at present, a source of much pride to the Gujarat government. But the protected area itself can only support about 300, so many lions live precariously outside of it—in fields and orchards interspersed with villages and towns, and crisscrossed by highways and railway tracks.

With development hemming them in, Asiatic lions routinely die in accidents. Since 2015 six were hit by trains and two by trucks, 13 fell into village wells and several others died of electrocution, according to the state government. (Many farmers use electric fences to fend off crop-threating wild animals such as deer and boar; lions occasionally get trapped in them and die.) Overall 184 lions perished in 2016 and 2017 as opposed to 310 over the preceding five years — a worrying jump in the mortality rate, even before the latest spate of deaths.

In early October researchers at India’s National Institute of Virology (NIV) and, separately, the College of Veterinary Sciences and Animal Husbandry examined blood and other samples from the dead lions. Confirming officials’ suspicions, they found CDV—a highly contagious airborne pathogen that usually infects members of the dog family — and Babesia, a tick-borne protozoan. The NIV team also recovered a complete CDV genome; alarmingly it turned out to be related to strains found in east Africa, where canine distemper in 1994 wiped out roughly 1,000 African lions, amounting to 30 percent of their population in Tanzania’s Serengeti National Park.

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In the villages around Gir canine distemper is endemic to domestic dogs — a major food source for lions living outside the protected areas. “Lions could either have caught CDV directly from them or from other carnivores — hyenas, jackals or leopards,” says Hari Shankar Singh, a member of India’s Wildlife Board and a former administrator in Gujarat’s Department of Forests. At the NIV’s recommendation, the government vaccinated all the Gir lions they had quarantined.

But it remains unknown exactly how CDV spread to the Gir lions. The virus can be present in an animal without causing sickness or death, notes Meena Venkataraman, a Mumbai-based wildlife biologist who runs a consultancy organization called Carnivore Conservation and Research. A detailed examination of clinical symptoms, along with postmortems and other detailed tests, are necessary to establish the extent to which CDV is responsible — and also to answer multiple other questions such as the prevalence of the disease in both lions and domestic dogs, she says.

On October 31 a dead lion cub turned up on a farm near Gir. According to Dushyant Vasavada, chief conservator of forests (Junagadh Wildlife Circle), it died of respiratory and cardiac failure caused by severe anemia and dehydration. These are symptoms of heavy tick infestation, indicating the possibility of Babesia infection. “The outbreak of CDV and Babesia protozoa may not kill a majority of Gir’s lions, but their threat looms large,” Singh says. He believes the underlying problem is not so much the presence of microbes and parasites (which is only to be expected) but rather compromised immune systems. “When immunity is lowered against the attack of any virus, the attack of CDV and Babesia turns fatal to the animal,” he says.

Whether or not immunity is in fact impaired — and if so, why — also remain open questions. In principle, inbreeding could lower immunity by highlighting any deleterious genes present in the existing population.

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Venkataraman doubts this is the case, however. Inbreeding can result in reduced survival rates for cubs; but she notes cub survival rates in Gir are comparable with or better than in similar habitats in Africa. Also, climatic factors such as drought can dry up water sources and make food hard to find, lowering immunity and aggravating infections.

The way forward

Once the latest outbreak is dealt with, India needs to institutionalize a response via disease management protocols, Venkataraman says. “We must have contingency planning; disease can occur,” she adds. “It’s our preparedness and honest evaluations of such situations that is critical.” She claims the Gujarat authorities currently have no action plan for preventing infections, screening for pathogens or dealing with disease outbreaks. Decisions such as vaccinating wild animals “should not be made at the 11th hour when animals are dying,” she says.

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Ensuring the long-term survival of Asiatic lions would require further measures, Singh notes. These would include the intensive use of genetics, forensics and virology to swiftly detect and respond to disease outbreaks; restoring habitats in the areas around Gir; closely managing the lions to reduce interactions with domestic animals; and moving a few prides to alternative sites.

But Gujarat has habitually balked at any move to relocate any of the lions. Regarding the animals as part of the state’s exclusive heritage, it insists they are safe in Gir. In 2013 the Supreme Court of India directed the immediate transfer of a few lions to another wildlife sanctuary that had been readied to receive them. The Court stated that preserving an endangered species was of paramount importance, overriding matters of regional prestige — but Gujarat did not comply with the court order.

G. K. Sinha, the principal chief conservator of forest and head of Gujarat’s Forest Force, did not immediately respond to e-mailed questions about the state’s noncompliance and findings about the recent deaths.

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Relocating some of the lions would maintain an ecological and biological distance between two populations—thus helping to avoid possible inbreeding and to contain the spread of epidemics, says Chellam — who in the 1990s led a committee of experts mandated by the Court to study moving Asiatic lions to a new sanctuary. The committee had suggested three alternative sites. Of them, the Kuno Wildlife Sanctuary in Madhya Pradesh State — which lies 300 miles east of Gir and has historically been part of the range of Asiatic lions — was found to be best suited for their re-introduction.

With Gujarat showing no sign of relenting, however, the threat that the Asiatic lion could be extinguished by the latest crisis or by future ones remains a possibility. It is risky to “keep all eggs in one basket” irrespective of their numbers, Chellam says: “You’ll lose all the eggs if you drop the basket.”


Jaideep Hardikar

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