Big Cats and Disease Management

by October 30, 2018 0 comments

Big CatsOutbreak of diseases poses major threats to big cats including the lions in Gir. A scientific wildlife health management system is the need of the hour.

The big cats — lion, tiger and leopard — are susceptible to diseases as they largely prey upon domestic animals, including dogs and pigs, which are a carrier of pathogens. Domestic livestock constitute over 40 per cent of the food for lions and about 60 per cent for the leopards. Dependency of the tiger on domestic livestock is also high but lesser than the other two big cats. Dogs are the main source of rabies deaths, contributing to about 99 per cent of all rabies transmissions to humans. Cases of leopard deaths due to rabies were reported during the British period. In absence of adequate report, it is difficult to assess deaths of tigers, lions and leopards due to rabies but higher possibilities exist.

The carcass of every rabies infected dog or livestock is eaten by the carnivores, primarily big and small cats, hyena, jackal, wolf, foxes, and honey badger. A few deaths of lions and tigers too were suspected due to rabies attack in the past. Vaccinating dogs is the most cost-effective strategy to prevent rabies in humans and carnivores.

The first fatal attack of Canine Distemper Virus (CDV) and Babesia Protozoa was confirmed in the Gir lions when 23 out of the 26 known infected lions died in a short period in September this year. Tigers and leopards are solitary animals and their social life is different from the lions. Except females with cubs, none of these two big cats live in groups. Thus, the death of each one of them due to such disease is usually not detected, and are reported as natural deaths. In the case of death of a nomad lion or a small group of lions, by virus or protozoans, incidence would have been ignored even with thorough high-level investigation of the disease. But it cannot be ignored when the number of deaths exceed half a dozen in a short period of just two weeks. The presence of virus or protozoans among the big cat is not rare but has never been reported because the science of virology has not been integrated with wildlife management.

In a majority of places, they do not die due to their immunity system. When immunity is lowered against the attack of any virus, the attack of CDV and Babesia turns fatal to the animal. Perhaps this was the case for large-scale deaths of Gir lions.

Two scientific institutes for the first time reported in 2011 about the lion death in Gir due to highly infectious Pestedes petits ruminants virus (PPRV). Active viral surveillance in neighbouring Gir villages for PPRV, similar to CDV, was also recommended by an institute. Subsequently, it appeared in newspapers that the four Gir lions sent to Etawah, Uttar Pradesh, died of CDV during 2014-16. This called for vaccination of dogs and other such animals against CDV. However, action could not be put in place due to some reasons.

Asiatic lions face serious threats to their future as about half of them live outside the core habitat of the Gir forests and hunt domestic livestocks,  along with livestock and blue bull. Lions in the peripheral zone also hunt domestic livestock in the villages or maldhari nesses. A large number of leopards hunt dogs along with other preys and sometimes their kills are appropriated by the lions. Probability of transmission of virus, bacteria and other such disease is very high in the Asiatic lions. Epidemic disease risks for lions in fragmented small populations become significantly higher as contact with domestic animal populations, including dogs, become more frequent as a result of alterations in microclimate and landscape ecology.

The tools to predict, prevent, and respond to these risks are not well established in conservation management. But deaths of Gir lions due to the fatal disease is expected to open a new chapter in wildlife management. Crucially, rescue operation and wildlife health management are the best in lion conservation landscape in our country but not enough to address the challenges effectively.

In Serengeti, the lions are prone to simultaneous outbreaks of CDV and Babesia Protozoa. Canine distemper is a virus that affects dog’s gastrointestinal, respiratory and central nervous systems as well as the conjunctival membranes of the eyes. CDV, a disease that results in encephalitis and pneumonia, is transmitted by domestic dogs; Babesiosis is carried by a tick-borne blood parasite called Babesia. Symptoms of the CDV attack include fever, eye infection, discharge from eyes and nose. CDV or Babesiosis alone aren’t the threats to lions in Serengeti. It is a combination of CDV with a high-level of exposure to Babesia that killed the lions in Africa in 1994 and 2001.

Co-infection by more than one pathogen can accelerate expected transmission rates and virulence of a disease. Environmental perturbations can also change the host parasite’s relationship. In a majority of the cases, lion populations are infected with at least one, and most with multiple pathogens, often with multiple strains of pathogens.

Scientists suspected that the disease — identified from blood and tissue samples as CDV — came from domestic dogs in the villages around the Serengeti perimeter. Blood samples from the dogs showed the presence of CDV. In the villages where lions hunt livestock, domestic dogs are very common. Canine distemper spreads mostly via sneezing. It was likely that the virus travelled directly to the Gir lions from the domestic dogs or it was more plausible that the lions caught the virus from other carnivores — hyenas, jackals, or leopards.

Hyenas and jackals are scavengers that frequent villages, and leopards hunt domestic dogs or eat carcasses. Lions would come into contact with these infected species at kills. In and around Gir forests, over 625 leopards hunt domestic animals, primarily dogs. The possibility of appropriating these kills by the lion is not ruled out. A mad leopard, infected by rabies, can challenge lion and what a lion can do to such leopard is well known. Lions are scavengers and they feed on dead animals. These animals, including naturally dead dogs, can be a source of transmission to the lion.

Although two dozen lions died of fatal diseases, similar incidences may be occurring in other carnivores too. Why is it that the wild dog population suddenly dropped in protected areas in central and south India, and then recovered in two-three years before the next drop? Why is it that the number of jackals is registering a downfall? Perhaps, a solution to their problem lies in scientific wildlife health management. Also, the fatal attack of CDV and deaths of lions in a large number can be a lesson to use the science of wildlife diseases in wildlife management.

Alternative home for Asiatic Lions: The Species Survival Commission of the International Union for Conservation of Nature published guidelines on strategic planning for species conservation, which have single population in one geographic region. The Asiatic lion is one of them which has the only wild population in the world in the Gir forests. A group of leading conservationists declared that an extinction crisis is facing the world’s largest carnivores, including the big cats. The super cats — lions and tigers — need very large area as they need huge tracts of natural habitat to survive. Due to their large size and threats, they are less resilient than many smaller species and less able to handle the threat.

Big carnivore population, restricted to a single site, face a variety of extinction threats from poaching, intentional killing and environmental factors. Catastrophes, such as an epidemic or fatal disease, remain the main factors for loss of species. Reintroduction of the last free-ranging population of Asiatic lions to an alternative site to ensure their long-term viability became a major conservation agenda. Considering this, the first trial to introduce Asiatic lion in Chandra Prabha Sanctuary in Varanasi was done in 1959 by translocating few lions but the experiment failed after initial success.

Subsequently, the Gujarat State Government ordered the Barda Wildlife Sanctuary in 1979 to establish an alternative for the Asiatic lion, but the decision remains on paper due to lack of a bold decision by the authority.  Subsequently, after a long exercise, Kuno Wildlife Sanctuary (Kuno WLS) in Madhya Pradesh has been identified as an alternative site. After a long legal battle in the Supreme Court, decision went in favour of Kuno Wildlife Sanctuary, but even five years after the decision, it has not been implemented.

The climate of the alternative site is a major issue which needs examination before the translocation of the animals there. The lion evolved and flourished in temperate and sub-tropical environment, and the climate changes, especially temperature variations, impacted its migration, dispersion and distribution in Europe, Asia and Africa since it evolution.

Review of climatic parameters of past and present lion areas across the three continents indicate that the lion perhaps never flourished in hot tropical environment, and lion habitats  may have a high risk of extreme temperature in the hot summer. At present, major populations continue to survive in sub-tropical environment in over two dozen countries, and in small populations in temperate and moderate tropical climate in Africa.

In India, temperature of the Asiatic lion distribution range in tropical climate is around the Gir forest. The shelter of evergreen riverine vegetation along the seven perennial or semi-perennial rivers and Prosopis cover along Shatrunji river or along the coast provide cool environment for the lions. Alternative site for lion in very hot environment of the Kuno WS in the Vindhyayan region is debatable. The logic of the survival of the lion in the north-west India 150 ago in Mini Ice Age (1300 AD to 1850 AD) does not hold ground.

Disappearance of the lion outside Gujarat coincide with the end of the Mini-Ice Age when average temperature in north India was lower than the present temperature. In fact, climate then in the north India was near subtropical. The distribution of the Asiatic lion since its entry in India to the present need examination with respect to the climate.

In background of these facts, the Government has few options which should be undertaken to minimise threat factors which can cause the extinction of the sub-species. First, the science of genetics, forensic and virology should be used intensively for long-term conservation of the lion. Second,  satellite areas should be managed in line of Gir protected area by enhancing administrative staff and restoring habitats. Third, an alternative site for the lions should be developed without delay. Barda Sanctuary is one of the good option. Success in this case is high because similar type of administration, with all facilities and know-how, can be transplanted there. If it is not done shortly or not possible due to some reason, the Government should not hesitate to develop an alternative site far away from the Gir forest.

Writer: HS Singh

Courtesy: The Pioneer

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