Recent Nipah Virus (NiV) outbreak in the state of Kerala, India has claimed sixteen lives so far including one that of a medical professional. After the quick recognition of the pathogen (NiV) on the very same day the infection claimed the second life, the state health machinery has quickly woken up against the disaster with management options. Trusting the scientific knowledge that the natural reservoirs of NiV are bats, the state Health Minister Smt. KK Shailaja told the media that the source of the virus are bats and they are found in the well of one of the patients who died due to NiV infection. She also hinted that the virus transmission must have happened through fruits bitten by bats. The virus was, later fond absent in the insectivorous bats mentioned by her but the screening of bats for NiV infection and antibody which fights against it is ongoing in the state. The number of cases getting reported area also coming down but the fear among the people persists, the fear is more about the natural reservoirs of the virus – bats.
Scientific studies on the nature of Nipah outbreaks and the bats
NiV was first detected in Malaysia during 1998. The research works after the Malaysian outbreak of NiV has confirmed the virus carrier potential of bats. Immediately after the outbreak, the presence of virus was, confirmed in five species of bats in Malaysia including one insectivorous species, farm pigs, and domestic dogs living near to the virus infested pig farms and absent in other wild animals and hunting dogs[i]. The detailed study of the genetic sequence of the virus from bats and infected human patients proved that the time between the spillovers of the virus from the hosts is very short[ii] and the whole outbreak which ended up in 105 human deaths could have originated from a single or perhaps two bouts of introductions of NiV from its bats to pigs[iii].
The next major outbreak, rather a series of outbreaks was in Bangladesh between 2001 and 2014. A spatial mapping of these series of outbreaks revealed that it occurred only in north-western and central part of the country and some in adjoining areas in India as well[iv] whereas bats were distributed all across the country. The out breaks were not only spatially clustered, but temporally too. All the case reporting were in winter and in some years extended to spring (between December and April). The outbreaks in Bangladesh resulted in establishing another way of transmission of the virus from bats to human which was through date palm sap, used to be collected and drunk during the beginning of the season of outbreaks.
More collaborative scientific studies happened in both the countries which established some basic facts. The presence of bats carrying NiV doesn’t mean that it will lead to an outbreak. In the backdrop of the Malaysian outbreak, Thailand the neighboring country also conducted a baseline survey of NiV among bats between 2002 and 04[v], which confirmed the presence of NiV in five bat species in the country. Surprisingly there were no outbreaks in the country since 1998. Some studies have also detected Antibodies which fight against the NiV in the bats from Haryana, India NiV as such was absent in their body, which shows high probabilities of these bats to be infected by the virus some time in their life span. In Malaysia the virus transmission from bats to human was through pigs[vi] where as in Bangladesh it was more or less direct through date palm sap consumption and bat hunting[vii],[viii]. A significant proportion of the reported cases were in fact, man to man transfer – which is a result of poor clinical management of the contagion.
In the meanwhile, it was also found that the virus spillover from bats are induced by different types of stress on the bat populations[ix]. This was not specific only to NiV rather on general virus spill over from Bats. The study has also established certain enabling conditions for the zoonoses transmission to human from bats. Jonathan H. Epstein from Kingston University who did a PhD on NiV transmission by bats confirmed that the shedding of virus may happen at any time from the bats, in absence of the enabling conditions (as described in the previous study mentioned) which never reaches man[x].
Precisely, while establishing bats as the reservoirs of the Nipah Virus, the research works so far have also identified two significant facts – certain environmental conditions (anthropogenic or non-anthropogenic) exerts stress in bats to spill the virus and certain enabling conditions are necessary for the virus zoonotic. The reason for human infection of the virus can be a result of simultaneous occurrence of these two. Any management of this virus infection including pre-emption of further outbreaks need a detailed understanding of these factors.
Aftermaths of Nipha Outbreak in Kerala
Immediately after the outbreak, the whole Kerala media, started publishing descriptions on the possibilities and means of virus transmission from bats to human and suddenly the bats of the state has depicted as horrendous creatures as in a scary story like Dracula. Even though bats are wild animals, their roosting sites are common in many villages in Kerala. At nights, they frequent in the backyards and farms around the houses feeding on fruits. Cutting of the roosting trees and occasional hunting by the bat meat lovers were the limited threats to the bat populations in the state.
After the news about bats being the reservoirs of NiV has spread, during the NiV infection awareness creation programmes in many of the villages in Kerala, demands came from people for eradication of bats from the human habitations. People even became apprehended to have their meals in banana leaves which is a common practice in the state, since bats frequent on banana plants feeding on fruits and sucking honey from flowers. Demand for prioritization of bat eradication in the virus outbreak management plans also emerged. Very soon bats may lose their natural roosting sites in the human habitations.
Possibilities of counter effects
The present epoch in the geological timescale is called as Anthropocene – a time in which the human activities influence the climate and environment. In a way by this word, mankind has declared itself as the most influential species of the time in this biosphere understanding the myriads of threats to the maintenance of ecological balance. Every day we see the evidences of anthropogenic ecological damages around us as catastrophe, natural and other disasters and new diseases. Almost all of the interventions which led to these catastrophes would have done for the convenience, safety and economic benefits of mankind.
What is emerging in Kerala is nothing different. Bats are being targeted as an easy elimination of the source of a human problem, even though there are sufficient number of studies which proves that – presence of bats or Nipah Virus in bats don’t mean that it can be passed to human beings, bats never spills virus all the time around and even if there needs some enabling conditions for the virus transfer to man and there are certain stress generating factors which induces the bats to spill the virus, people just think about eliminating the reservoir animal populations from their vicinity.
Bats are very significant species which provides many ecosystem services including pollination and seed dispersal. Many of them are rare and endangered species. A mass elimination bats can cause serious ecological issues. Moreover, in absence of knowledge about what are the factors which creates stress in the bats to spill the virus, stressing them through high level of disturbance at the roosting sites, loss of roosting sites and human attack on colonies etc can be counter effects. These may make them to shed more virus and there by the situation can worsen.
Even believing that the outbreak is bat origin in Kerala, the need of the hour is to identify the factors which enabled the zoonotic transfer of the virus and also the factors induced the bats to spill the virus. Until we get a clarity on these issues, people in Kerala should keep the bats out of any stress for their own safety and environmental benefits. Conservation and maintaining the harmony of nature is the best way to be safe.
Final Note – Zoonosis is an ecological phenomenon. Here, we miss the ecological angle of these disasters during its management. So the ecologists are seldom included in the task forces. These situations are – by and large, managed by the medical experts (both human and veterinary) and other administrative machinery. This is a major reason for missing the conservation elements in outreach. This also may become reason to miss the complex environmental factors playing crucial role in emergence of the disasters.