Kerala reports Nipah thrice in 4 years. Is a new variant prevalent in South India?

Kozhikode: It was recently confirmed that bats were the source of Nipah Virus detected last time in Kozhikode district.

Health Minister Veena George declared Kozhikode district Nipah-free since there were no Nipah cases reported for 42 consecutive days.

Though the state can find solace in the fact that things are under control for the time being, some moot questions regarding the outbreak remain unanswered.

How was the particular virus transmitted to the body of a human being and what is the present status of the Nipah monitoring system and research in Kerala?

It is true that the virus holds no imminent threat to the public with not a single case being reported during its 42-day double incubation period. But it is a cause of concern that Nipah was reported in a densely populated state like Kerala on three occasions.

It was on September 4, 2021 that the 12-year-old Muhammed Hashim, a native of Pazhoor in Chathamangalam in Kozhikode district, was found infected with the virus. The next day, on September 5, he died. The parents and health workers who came into contact with the boy were not infected by Nipah.  The samples taken from the pet animals in the area were negative. No trace of Nipah was found in the Rambutan fruits collected from the area.

But the latest tests conducted by the Pune-based National Virology Institute of India on bats caught from the area found the presence of antibodies of Nipah. The bat samples were taken from Thamarassery and Kodiyathur panchayats lying next to Chathamangalam from where Nipah cases were reported this time.

There are many study reports which confirm the presence of Nipah in Kerala in 2018 and 2019. In 2018 and 2019, the strains of Nipah were found in the bats belonging to the Pteropus genus. But this time, the Nipah antibody was also found in the bats belonging to the Rousettus genus apart from Pteropus type.

IDENTIFYING BAT CLUSTERS  

According to Dr Arun Zachariah, Veterinary Surgeon, Forest Department, there is a need to conduct more surveys about the bats that cause this disease. "The results of the latest studies are not with the Forest Department. Anyway, we hope that more studies would be conducted under the initiative of the State Government. This time, the spread of Nipah could be curbed because of the precaution we had taken against COVID-19. Effective steps were also taken to contain the spread of Nipah," he said.

Researcher and science writer Vijayakumar Blathur said that the presence of large-scale virus-borne bat clusters might have led to recurring attack of Nipah in Kozhikode district.

"It is a matter of great concern that such a virus was reported thrice during the last four years in Kerala, where the density of population is very high. So, there should not be any room for complacency. We should strengthen the monitoring system. We should undertake scientific studies without creating panic among people. Conducting studies on bats is not that easy.

The collection of samples itself is risky. After identifying the clusters of bats through continuous observation, the next step is to devise a strategy to contain the spread of disease. It is important to create scientific awareness among people by educating them that Nipah viruses are not  bacteria and they will survive and thrive only in a very suitable ecosystem, unlike bacteria.  Such kind of sensitisation would put an end to unwanted fear among the public. "

SOLUTION IS NOT KILLING BATS

According to Vijayakumar, many viruses are actively lurking inside the bats because of their evolutionary specialities. And, some bats have Nipah virus inside. Such viruses are there inside their body and does not come from any external source.

This virus is transmitted to a newborn bat from its mother at the time of birth itself. Bats do not beget many progenies. A female bat gives birth to only one offspring a year.

The virus-borne bats living in a particular habitat may go to other places owing to the destruction of their existing ecosystem.  Bats have high immunity power. If you throw them out from one place, they will create clusters in another area very easily. So, the idea of finishing off bats by way of destruction and thereby ending the Nipah threat is foolish,” Vijayakumar said.

AVOID DIRECT CONTACT

According to Dr Sreehari Raman, Assistant Professor with the Wildlife Science Forestry College under the Kerala Agriculture University, about 66 types of viruses have been found inside bats so far. Only Rabies and Nipah were found in Kerala. But there are very few chances of these two viruses coming out of the body of the bats.

"The Nipah antibodies were found in Pteropus and Rousettus types of bats. Both these types are fruit bats. In Kerala, there are six varieties of fruit bats. There are 42 types of bats which eat insects. So, it is not practical to completely wipe out the presence of bats from our farms and house premises. We easily identify larger types of bats found in trees. But you may not notice small bats, which are usually found in the ceiling of the traditional Kerala houses. Bats will not create any problem if we do not come into direct contact with them."          

SOUTH INDIAN VARIANT

The Indian Council of Medical Research (ICMR) has already made an observation that there is a high chance of the existence of a south Indian variant for Nipah, while taking into account the disease  outbreak in Kerala in 2018 and 2019. The ICMR made such an observation in a study report published in the February 2020 issue of the BMC Infectious Diseases.

The report assumes significance especially in the light of reporting of fresh cases in Kerala in 2021. The ICMR study report also says that Nipah virus-borne bats might be active in many more districts in Kerala and steps be taken to enforce a mechanism for special monitoring of the virus.

As of now, there are only Bangladesh and Malaysia variants for Nipah disease. But the virus found in Kerala differed from those two variants in terms of genetic structure. It differed 1.96 percent from the Bangladesh variant. The difference with the Malaysian variant was 8.42 percent. It was also different from the structure of the virus found earlier in the North Eastern States. According to ICMR, a new variant of Nipah Virus (India I) might be prevalent in South India.

In short, all studies point to the fact that Kerala should take urgent steps to conduct more observations and pursue research work to resist any further outbreak of the disease.