Don’t Just Blame Bats for Nipah Outbreak: Take Precautions, Improve Public Health

by Sushma Rao on May 31 2018 9:35 AM

 Don’t Just Blame Bats for Nipah Outbreak: Take Precautions, Improve Public Health
The death toll caused by the Nipah virus (NiV) infection from Kozhikode and Malappuram districts in the state of Kerala, has totaled to 14 lives in the month of May.
Siblings Mohammed Sadik (26) and Mohammed Salih (28), died on May 5 and May 18 respectively in Perambra of Kozhikode district. Following them their aunt Mariam (50) passed away on May 19. Lini who worked at the Taluk Hospital in Perambra, and had nursed Salih at the hospital died on May 21 due to the fever. That was the beginning of a panic outbreak in Kerala.

It was identified that there had been bats in the dug well, which was the main source of drinking water for the Sadik-Salih family in Perambra. This created a huge fear among the public that people even called for mass culling of bats.

However, the disease itself was contained quickly before it could become an outbreak. On May 24, the Health Ministry, Government of India issued a media release stating that a multi-disciplinary team that was reviewing the situation from Kerala had concluded that "the Nipah virus disease is not a major outbreak and only a local occurrence."

On May 25, there was news that added further confidence on the situation. Body fluid samples collected from the bats that were found hanging in the well in the Sadik-Salih household turned negative for Nipah virus. The National Institute of High Security Animal Diseases at Bhopal confirmed this after testing the samples. Further, samples sent from cattle and pigs in the vicinity that were also sent tested negative for Nipah virus.

According to the World Health Organisation's (WHO) Nipah Fact Sheet, the virus can be transmitted to humans from animals (bats, pigs), and can also be transmitted directly from human-to-human. In 2001 it appeared in Bangladesh and same year the Nipah virus outbreak happened in Siliguri in West Bengal in India. Of the 65 infected in Siliguri 45 persons died.

"Human infections range from asymptomatic infection, acute respiratory infection (mild or severe) and fatal encephalitis," states the WHO fact sheet. There are no specific drugs or vaccines for NiV infection. Intensive supportive care is the recommended treatment.

There is relief in Kerala that the infection did not spread into an outbreak and is now more or less under control. However, from where the infection started is the question that continues to be a mystery. Bat specialists were fairly sure that the bats hanging on the laterite walls of the dug well in the Sadik-Salih household were not the culprits.

"The bats hanging in the dug well were insect-eating ones, and insectivorous bats have not been seen to be the carriers of Nipah virus in the past," said P. O. Nameer, professor and head, Centre for Wildlife Studies, College of Forestry of the Kerala Agricultural University.

"In my 20 years of experience studying bats in Kerala there has been no evidence of fruit-eating bats inside wells," said Nameer adding that what could be considered as a suspected carrier in Kerala "is the great Indian fruit bat, also known as the Indian flying fox (Pteropus giganteus)."

It is not clear as to how, where and from whom the first infection happened in Perambra.

Bats have been blamed as the cause for Nipah as they are the natural host of the virus. It is due to this reason that the Kerala Government had to strictly warn public not to indulge in any activities that can harm the animal.

Merlin Tuttle, American ecologist, founder & executive director of Merlin Tuttle's Bat Conservation told Mongabay-India in an email: "Virtually every animal species that has been carefully studied has some virus of potential risk to other species. In the past four decades, so-called 'emerging diseases' have killed fewer than 20,000 people worldwide, and there is no more than unsubstantiated speculation for blaming even half of those deaths on bats," he added.

He also said that bats in reality have one of the world's finest safety records when it comes to living with people. Hundreds of bat biologists, millions of people who eat bats, and the millions more who share cities with huge bat colonies are no less healthy than others.

In an email to Nameer, Paul Racey, a leading authority on bats, retired professor at the University of Aberdeen and the chair of the Bat Specialist Group of the International Union for Conservation of Nature (IUCN), said that the disease spreads mainly by drinking palm sap that has been infected with the Nipah virus by the greater Indian fruit bat Pteropus giganteus. Preventing bats' access to the sap collection pots has reduced the infection rate in other parts of the world.

Since palm sap toddy is a common drink in Kerala, experts advise avoiding the drink at present. This is better way to prevent the infection from spreading than harming the fruit bats.

"Culling of bats has to be totally avoided even if tests show some of the fruit bats in the region are carrying Nipah virus," Nameer emphasized.

A WHO report on Nipah Virus Infection states that "there is strong evidence that emergence of bat-related viral infections communicable to humans and animals has been attributed to the loss of natural habitats of bats." It further adds, "As the flying fox habitat is destroyed by human activity the bats get stressed and hungry, their immune system gets weaker, their virus load goes up and a lot of virus spills out in their urine and saliva."

Both Nameer and Ekbal emphasize the need for better public health awareness and preparedness.

According to the WHO report, 600 Nipah cases were reported in the world from 1998 to 2015. Among this almost 50 percent of the infected patients died.

"This is a small number considering the world statistics for other diseases. In Kerala 10 people die daily in road accidents. So there is no need of a panic. This virus can be tackled with precautions," Ekbal said.