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Bats are known or suspected to be the natural reservoirs for many novel and recently emerged pathogenic viruses such as Nipah, Hendra, Marburg, Ebola and the Severe Acute Respiratory Syndrome (SARS) virus. There is increasing scientific evidence that the SARS-CoV2 virus that causes COVID-19 also originated in bats.
In India, many people are dependent on the ecosystems they live in, and the various services those ecosystems provide, for example, water, clean air and pollination. This raises questions about protecting bats staying in close vicinity to people.
There are nearly 128 species of Bats present in India; over 1,200 species of bats exist worldwide. They emerge from their roosts in trees, caves, rock ledges, temples and buildings.
|Read more: All you need to know about Nipah virus|
Significance of Bats
Environmental benefits: They devour insects, including agricultural pests and disease-causing mosquitoes; in farms, fields, forests, grasslands and around human settlements.
Some bats’ sip nectar, pollinate flowers, eat fruits, and spread the seeds of many important tree species including wild varieties of bananas, guava, cashew, mango, figs, mahua and other fruits.
Economic and Social benefit: A study in Thailand has shown that pest biocontrol provided by just one species of bat prevented the loss of 2,900 tons of rice per year — equivalent to savings of $1.2 million, and provision of meals for 26,200 people annually.
Bat droppings (guano) mined from caves are widely used as a fertilizer for agricultural crops, as they have high concentrations of nitrogen and phosphorous.
|Read more: Govt. report flags lapses in “filovirus study” among Nagaland bats|
What are the challenges associated with bats and their harms?
No proper study: There is almost no study on the ecosystem services provided by bats in India. So, there is a widespread misunderstanding of bats and their critical role.
Growing fears of disease spread: Due to COVID-19, the world has suddenly become aware of the several viruses bats carry because they could spill over to humans. So, there is a growing fear among people about further disease transmission from bats. But such spillovers are unusual and rare events and tend to occur when there is increased contact between humans and wild hosts.
|Read more: Covid-19 pandemic cut life expectancy by most since World War II|
Why do bats never fall sick?
Bats are reservoirs for viruses, but they never fall sick. Flying results in toxic by-products that could damage cell contents. Bats have evolved mechanisms to avoid such damage by suppressing their immune systems.
Scientists think that such suppression results in a continuous auto-immune response, which helps them combat infections and control virus propagation. This ability to limit excessive inflammatory response ensures they do not overreact to viral infections and protects them from multiple chronic age-related diseases.
Note: Inflammatory response is responsible for the adverse effects of such viruses in infected humans.
Why is there a higher susceptibility of spread of disease from bats now?
Over the last several 100 years, humans have significantly modified the surrounding landscapes. This results in disturbances to bat roosts and forcing them to change their ‘homes’. For example, activities such as mining destroy the natural cave systems that bats live in.
Scientists have shown that when bats are disturbed, they become stressed and could shed viruses that they carry, increasing the risk of spillover to humans. This suggests that human habitat destruction makes bats move closer to human habitation, resulting in stressing them, and in turn viral shedding.
What can be done?
Maintaining ecological balance: The COVID-19 pandemic has compelled humans to maintain a fine ecological balance and ensure humans – Bats co-existence. This is important for the cure for SARS.
Conduct adequate study: Adequate study has to be conducted to know more about the ecology of bats, even in the context of viruses. A study has to be conducted to find out about viruses shed by bats and their time, either throughout the year or seasonally.
|Note: The rich biodiversity and cultural diversity in India serve as an excellent and unique place for such studies. The National Centre for Biological Sciences (NCBS-TIFR), an aided Centre of the Department of Atomic Energy (DAE) is carrying out sero-ecological studies on the human-bat interface among Bomrr clan in Nagaland.|
The NCBS is also in the process of sequencing whole genomes of bat viruses. This study could help build a bank of virus genomes.
Use traditional knowledge: Several indigenous people had understood the importance of giving enough space to all animals, including bats. For instance, some tribes have isolation practices such as quarantine following hunting. The Bomrr clan in Nagaland have traditionally celebrated the annual bat harvest for many years. Yet, there has been no major disease outbreak among the Bomrr clan. So, local practices and traditions could serve as a guide for minimising the risk of infectious disease spillover from bats in the future.
Make sensible precautions: Such as minimise direct interactions with bats by avoiding handling or eating bats, and not eating fallen fruits gnawed by them.
In the longer term, people should work towards restricting and reversing land-use change practices that are bringing us in greater contact with animals that may harbour ‘emerging infections’.