Fruit bats are widely suspected to have caused the Nipah outbreak, which has already claimed 14 lives in Kerala since being detected on May 20, but the state’s animal husbandry department is yet to send them for testing to the National Institute of High Security Animal Diseases in Bhopal.

NN Sasi, the department’s director, said his investigators are currently catching fruit bats in Changaroth, the ground zero of the outbreak. “We haven’t sent the samples from fruit eating bats so far,” he said.

But they hope to send them in three days, he added. “Fruit eating bats are rare in Changaroth,” he explained. “The Bhopal lab has demanded at least 50 samples. We have got 20 so far. Sample collectors are equipped with personal protection gear. I hope the test results will be out in the first week of June.”

The animal husbandry department is facing fire for “confusing the public” about the origin of the deadly outbreak. On May 25, the department released the test results of samples collected from insect-eating bats found in the well of a family in Soopikkada which has lost four members to Nipah. The tests, conducted at the Bhopal laboratory, returned negative for Nipah and many local TV news channels went to town claiming that bats were not the carriers of the virus.

Dr G Arunkumar, head of the Manipal Centre for Virology Research who has been working closely with the Kerala health department, said the animal husbandry department was not supposed to release the results. “It created a lot of confusion,” he said.

Dr KP Aravindan, former professor of pathology at the Government Medical College Kozhikode, said the department should have sent samples from fruit bats much earlier. “It is a proven fact that fruit eating bats carry Nipah virus,” he said. “I don’t understand why they delayed it.”

He also questioned why the department sent samples from insectivorous bats in the first place. “Insectivorous do not carry Nipah virus,” he explained. “It is a fact.”

Indeed, in all previous Nipah outbreaks in Bangladesh, Malaysia and India’s West Bengal, fruits bats were found to have transmitted the virus to human beings.

The World Health Organization has included Nipah in its priority list of emerging diseases that could cause a global pandemic, along with Crimean Congo fever, Ebola, Middle East respiratory syndrome coronavirus and Zika.

Sasi defended his department. “We knew that bats caught from the well belonged to the insect eating variety,” he said. “But we didn’t want to take any chances.”

Test results of samples collected from insectivorous bats that confused the public.
Test results of samples collected from insectivorous bats that confused the public.

Seeking a cure

Public health experts said identifying the source of the virus is key to containing the infection and taking preventive measures against future outbreaks.

Aravindan suggested that genome sequencing of the virus would reveal the characteristics of the strain that has appeared in Kerala. “Scientists have so found two broad strains of the Nipah virus, the Bangladesh strain or B-Strain and Malaysia strain or M-Strain,” he said. “Sequencing of genome can help the scientists find whether it is similar to M-Strain or B-Strain.”

The Nipah outbreak in Malaysia in 1999 was found to have been caused by a strain with a 30% mortality rate while the Bangladesh outbreak in 2001 involved another strain that killed 70% of those infected.

The Kerala government has sent around 50 doses of human monoclonal antibody drugs to treat Nipah infections at Kozhikode Medical College. But Aravindan is doubtful of their effectiveness. The antibody was used to treat patients infected with Hendra virus, which is considered to be a close cousin of Nipah and was first observed in horses in Australia in 1994.

Arunkumar, though, is optimistic. “Hendra and Nipah viruses have many similarities,” he said. “The antibody is effective in treating Hendra. I hope it will also act effectively in Nipah-infected patients.”