THIRUVANANTHAPURAM: The re-emergence of the Nipah virus (NiV) in Kozhikode after a gap of three years highlights the continued risk of the recurrence of the bat-borne zoonotic virus that causes near-annual outbreaks of fatal encephalitis in Kerala at regular intervals.
Worryingly, Kerala is still not adequately equipped to tackle the health threat posed by the Nipah virus despite confirming it to be present in the bat population of the state. Two years after the incident, the temporal extent of NiV transmission continues to pose spillover risk to humans wherever they interact with Pteropus fruit bats that carry the virus.
As Kerala confirmed the Nipah virus for the third time, S Nandakumar, Disease Investigation Officer, State Institute of Animal Diseases, who was part of the pathological investigation team which carried out the study on the bats, explained the challenges being faced by the state. Excerpts.
Last time, we could confirm the presence of anti-Nipah bat IgG antibodies as well as presence of the Nipah virus in the bat population in the affected regions of the state, but we failed to stop the recurrence. Your comments.
It's true that we have confirmed the presence of NiV in fruit bats in the state, but restricting the opportunity of spillover to humans has certain limitations. Bats are natural reservoirs of the Nipah virus and they used to secrete or excrete the virus through saliva or faeces especially during the period of their stress like breeding or while losing their habitats etc. In most host animals we can identify the clinical symptoms, but it's not possible in bats as they are the natural carriers of the virus. So the possibility of ruling out or checking the recurrence completely is not so easy in the state.
What are the main hurdles for checking the recurrence?
In fact, the state has a considerable number of bat populations and subjecting all of them for sample study has certain limitations. Second, the state requires a permanent multidisciplinary team involving experts from various departments to study the influence of viral dynamics in bats and their temporal and spatial distribution in the long term.
What do you think about the cause of origin for the latest report of Nipah in Kozhikode?
I don't think the goat might be the host of the virus as estimated by the initial findngs. It is highly unlikely for the child to get the virus from the goat as goat and cow naturally would not transmit the virus to humans. Pig is the real host of the virus. In this particular case, more specific study is needed to ascertain the origin of the disease.
Though we confirmed the presence of the virus in the bat population, we couldn't find the origin of cases last two times. In this backdrop, do you think it is almost certain for a reemergence of cases at regular intervals in the coming years?
In the present milieu, the chances are high for the relapse of the disease in the coming years. The bat population is the natural reservoir of the virus and they can shed the virus at any time of the year and at any place.
Why are the Nipah cases limited to Kerala as other parts of the region have fruit bats of the Pteropodidae family and Pteropus genus, the natural host of the virus?
It's very intriguing and requires detailed study to find out the reasons for it. The public health system of Kerala is very strong and it is known for early detection of many diseases and prompt actions. Maybe this would be the one reason. Second, we have to hold a detailed study of causes or symptoms that led to unexplained deaths in the previous years at various hospitals in different regions including outside the state. Only then can we give a satisfactory answer for it.
Is there a chance for Nipah to reemerge in the same place where it was earlier confirmed?
There is no point in that argument. The same species of bats are commonly found in various parts of the state and the virus always sustains in living cells.
ALSO WATCH: