THIRUVANANTHAPURAM: Experts have suggested a detailed ecological study of bats in the state to understand the repeated Nipah outbreaks. The suggestion is in the backdrop of the findings by the State Institute of Animal Diseases (SIAD) that none of the samples collected from Chathamangalam in Kozhikode, where a 14-year-old boy died of Nipah recently, tested positive for the virus.
A periodic collection of samples and screening to assess the vulnerable bats are essential to establish the epidemiological link of Nipah in Kerala. Otherwise, the Nipah outbreak could be an annual affair, according to experts.
The SIAD had collected body fluids of goats, samples from the carcasses of bats and their droppings, and bat-bitten samples of fruits and screened these at the High Security Animal Disease Laboratory in Bhopal. The samples tested negative for the virus, proving a challenge to the efforts of the state to establish the link with the boy’s death in Kozhikode. Now, the state is awaiting the test results of the samples collected by the team deputed by the National Institute of Virology (NIV), Pune.
Dr S Nandakumar, assistant director and disease investigation officer of SIAD, said, “It is crucial to establish the source of the virus or how it is transmitted to human beings to check the recurrence of Nipah or reduce the impact of the disease in the state. But sadly, during the last two times and in the latest episode, we couldn’t establish the link. It means there is a strong chance for the reemergence of the disease in the state at regular intervals.
“The need of the hour is to hold a detailed periodic study on the habitats of bats to find out vulnerable places or roosters, the data of which has to be subjected for detailed inter-disciplinary study to find out the circumstances in which the virus was transmitted to human beings in Kerala. After the first phase of the study, we have to hold a systematic periodic study on the host species like pigs or other animals which can be an intermediary between bats and humans.”
Dr Bipin KC, head in charge of Veterinary Clinical Complex, Pookode and faculty of Veterinary Epidemiology and Preventive Medicine, here, said, “A continuous surveillance system is very essential to find out the high-risk and low-risk times for the virus transmission. We still don’t have any data to create a model to issue periodic health advisories for people. Only a detailed periodic study on the bat habitats across the state can find out the reasons for the virus transmission and other factors related to spillover of the virus,” he said.
Not only study, an interdisciplinary approach based on the ‘One Health’ system has also to be developed to take on the challenges posed by the infectious zoonotic diseases, say experts.
On Nipah trail
Less than 100 samples collected from goats, bats and fruits from Chathamangalam in Kozhikod and screened at the High Security Animal Disease Laboratory in Bhopal tested negative for Nipah virus During the 2018 Nipah outbreak in Kozhikode, samples of 52 Pteropus giganteus bats were collected and 10 of them (19%) were found positive for Nipah by ‘Real Time qRT-PCR’ testing. The viral strain in bats had then close to 100% similarity with the human NiV strain identified then In 2019 when one case was reported in Ernakulam, samples from 36 Pteropus bats tested for Nipah and 12 of them (33%) were found positive.