How did Nipah virus spread?

Five species of fructivorous bats commonly found in Kerala

Debate is raging over the bat species that might have served as the reservoir of the Nipah virus in the State as scientists wait for the virological reports to get to the bottom of the issue.

While most of the scientific literature available on the disease cites fruit bats as the natural host of the virus, an analysis by the World Health Organization and Food and Agriculture Organization had identified insectivorous bats too as the host.

Suspecting that the insectivorous bats roosting in wells could have spread the disease, authorities have sealed the well, the source of drinking water for the family in Changaroth where the disease struck. P.O. Nameer, Head, Centre for Wildlife Studies, College of Forestry, Kerala Agricultural University, says the campaign against insectivorous bats is a misguided one. The virus on insectivorous bat was reported in 2001 from Malyasia.

Various research agencies had identified fruit bats as the natural reservoirs of the virus. Five species of fructivorous bats, including the two forest species, are commonly found in Kerala. It’s the Indian flying fox, a frugivorous species, that is suspected to be the host, he says. The unfounded scare about bats roosting in wells could lead to panic against use of well water and killing of the bat species. Adopting improved hygienic measures like using boiled water and discarding the bitten fruits and not disturbing the bat habitats was the solution, he said.

Quoting an analysis conducted in Malaysia, a Nipah manual brought out by the FAO states that “Nipah viruses were found in 21 bats from five species (four species of fruit bats, including two flying fox species, and one insectivorous species although only two flying fox species showed a substantial seroprevalence.)”

Though the WHO’s emergencies preparedness and response to Nipah had stated that the “natural host of the virus is fruit bats of the Pteropodidae family, Pteropus genus,” there is also a report on isolation of the virus from an insectivorous species. A WHO report also quoted a seroepidemiologic study in Malaysia, which “implicated four fruit bat species,

Pteropus hypomelanus, P. vampyrus, Cynopterus brachyotis, Eonycteris spelaea , and an insectivorous bat,

Scotophilus kuhlii .” The species kuhlii is also found in Kerala, referring to the WHO report, said Sreehari Raman, a researcher in bat at the Chinese Academy of Science, Beijing. However, Dr. Nameer contended that the species kuhlii was not reported to be roosting in the wells.

The possibility of some of the victims or persons in contact with them consuming bat meat cannot be ruled out. There had been reports of people consuming the animal's meat for bronchial disorders, which could have triggered the transmission of the pathogen from animals to humans, Mr. Raman said.

P. S. Easa, a wildlife expert, decried the reported culling of bats and disturbances to their habitats in the wake of the outbreak of the disease. Adopting personal and societal hygiene and following safe food practices can only save the situation, he said.