Batting for an important but misunderstood species

Imagine it is evening in our countryside, with groups of people returning to their homes from fields, factories and forests. At the same time, hordes of winged mammals, called bats (about 128 species in India, more than 1,200 species worldwide) emerge from their nests in trees, caves, rock ledges, temples and buildings. Bats and humans have lived together since ancient times. Throughout the night, these bats feed on insects in fields, fields, forests, meadows and around our homes, including agricultural pests and disease-causing mosquitoes.

Some bats drink nectar, pollinate flowers, eat fruits, and disperse the seeds of many important tree species, including wild varieties of banana, guava, cashew, mango, fig, mahua, and other fruits. A study in Thailand showed that insect biocontrol provided by just one species of bat prevented the loss of 2,900 tons of rice per year – or a savings of $1.2 million, and food for 26,200 people annually. Bat droppings (guano) extracted from caves are widely used as fertilizer for agricultural crops because they contain high concentrations of nitrogen and phosphorus.

role in disease transmission

Unfortunately, despite these important roles, bats are the most misunderstood of all animals. In India, we have almost no studies on the ecosystem services provided by bats. With increasing scientific evidence that the SARS-CoV2 virus, which causes COVID-19, originated in bats, further disease transmission from bats is increasing.

An important and unique characteristic of bats is that they are known or suspected to be natural reservoirs for several novel and recently emerged pathogenic viruses such as Nipah, Hendra, Marburg, Ebola and coronaviruses that cause severe acute respiratory syndrome. cause. Despite being a storehouse of viruses, bats never get sick. Flying is a very stressful business, and it results in toxic by-products that can damage cell contents. Bats have evolved mechanisms to avoid such damage by suppressing their immune systems. Scientists believe that such suppression results in a sustained auto-immune response that helps them fight off infection and control the spread of the virus. Interestingly, this ability to limit the excessive inflammatory response (which is responsible for the adverse effects of such viruses in infected humans) ensures that they do not overreact to viral infections and are linked to many chronic age-related diseases. save.

In other words, bats have also inherited an immune system that protects them from viruses to help them fly long distances. The same immune system also slows their age, and makes them live longer. They are among the longest living mammals for their body size.

Due to COVID-19, we have suddenly learned that bats carry a variety of viruses as they can spread on us. But such spillovers – the transmission of pathogens from their natural hosts or reservoirs to novel hosts such as humans – are uncommon and rare events, and occur when there is increased contact between humans and wild hosts.

Over the past several hundred years, humans have significantly modified the landscapes around them – deforestation, clearing of land for agriculture and development – ​​resulting in disturbances to the bats’ habitats, and allowing them to live in their ‘homes’. ‘ has been forced to change. Activities such as mining destroy the natural cave systems in which bats live. Scientists have shown that when bats are disturbed, they become stressed and can release the virus they carry with them, increasing the risk of spillover. This suggests that human habitat destruction moves bats closer to human habitat, resulting in stress to them, and in turn causing viral shedding.

The COVID-19 pandemic has forced us to look back at the mistakes we made in destroying this microscopic ecological balance, and study how bats and humans can coexist in some areas. This is as important as the search for a cure for SARS. Even so, we still don’t know much about the ecology of bats, even in terms of viruses. Are spillovers more likely in areas with more bat species? Are viruses shed by bats throughout the year or only seasonally?

Studying the human-bat interface

Many indigenous peoples understood the importance of giving enough space to all animals, including bats, when they lived with them. Some have isolation practices such as post-hunt quarantine. They are dependent on animals and nature, and have achieved a balance without harming both sides. For example, the Bomar clan in Nagaland has traditionally celebrated the annual bat harvest for many years. They gather at a place called Mimi to smoke a cave full of bats and kill them for consumption as soon as the bats start coming out. In the process, bats bite or scratch them. Nevertheless, there have been no major disease outbreaks in the Bomer clan. To understand how and why Bomer bats are immune to the virus, the National Center for Biological Sciences (NCBS-TIFR), an aided center of the Department of Atomic Energy (DAE), is conducting sero-ecological studies. This man-bat interface. They are exploring the microbial diversity associated with bats, and also investigating serology (antibody responses to known viral families) to determine which part of this diversity is potentially pathogenic. So far, they have found: genetic prevalence/detection of multiple bacterial and viral families (between 3%-100% of bats) and evidence that both bats and humans share an antibody response to certain viral families, which causes spillover signal of.

NCBS is also in the process of sequencing the entire genome of the bat virus. This study can help build a bank of virus genomes as a baseline to prepare for any potential future outbreaks. Local practices and traditions can serve as a guide for us to understand how we should reduce the risk of transmitting infectious disease from bats in the future. The rich biodiversity and cultural diversity in India serves as an outstanding and unique place for such studies.

some precautions

But the fact is that bats carry many viruses. So how can we coexist with them? We can take some sensible precautions that minimize our direct interactions with bats – such as avoiding handling or eating bats, and not eating fallen fruit bitten by bats or fruit likely to be contaminated with bat fluids Eat. This will reduce the risk of leakage to a great extent. In the long term, we must work toward restricting and reversing land-use change practices that are putting us in greater contact with those animals, and increasingly emphasizing those animals that cause ’emerging infections’. can give asylum.

restore balance

In India, many people depend on the ecosystems in which they live, and the various services provided by those ecosystems, for example water, clean air and pollination. Over the past few decades, habitat destruction and land use change have affected much of India. We can regain this balance with nature and animals through a combination of habitat restoration and coexistence with wildlife such as bats. Integrated approaches such as OneHealth, where human health is linked to the environment and animals, can result in the best possible outcomes. Any such future will require a global commitment to reducing habitat loss and to the conservation and restoration of our natural habitats and biodiversity. A world with fewer bats around us would be one that causes agricultural pests to cause more crop damage, increased incidence of other diseases such as those transmitted by mosquitoes, and also without mahua.

Sushma Taishe is Joint Secretary, Department of Atomic Energy (DAE), Mumbai. Uma Ramakrishnan is Professor at the National Center for Biological Sciences, TIFR, an aided center at the Department of Atomic Energy (DAE), Mumbai.