Unfortunately, despite the critical roles bats play such as devouring insects in farms, fields etc., including agricultural pests and disease-causing mosquitoes and spreading the seeds of many important tree species – bats remain among the most misunderstood of all animals.
With scientific evidence mounting that the SARS-CoV2 virus that causes COVID-19 originated in bats, there are growing fears of further disease transmission from bats.
GS-III: Environment and Ecology, GS-III: Science and Technology
Dimensions of the Article:
- Bats and the ecosystem
- About Zoonotic Diseases
- Role of bats in the spread of disease
- Ecological imbalance
- Human-bat interface
- Details of Increased Zoonotic Disease
- Anthropogenic factors and Zoonotic Diseases
- Views of CHIROPTEROLOGISTS (THOSE WHO STUDY BATS) on Villainizing bats
Bats and the ecosystem
- Bats are winged mammals and 128 species of bats in India and 1200 across the world can be found. The Important roles played by bats are:
- They destroy insects in farms, fields, forests, grasslands, and around our homes including agricultural pests and disease-causing mosquitoes by eating them up.
- Some bats also pollinate flowers, sip nectars, and spread the seeds of many important trees including a wide variety of guava, banana, mango, and other fruits, etc.
- Evidence from the study has claimed that one species of bat prevented the loss of 2,900 tons of rice per year or the meals of 26,200 people annually by simply providing pest bio-control.
- Excrements of bats known as guano are widely used as fertilizers for agricultural crops as they are rich in phosphorous and nitrogen.
- In India, there is no study on the roles played by bats in the ecosystem. Despite the above-mentioned roles, bats have always remained misunderstood species.
About Zoonotic Diseases
- The word ‘Zoonosis’ (Pleural: Zoonoses) was introduced by Rudolf Virchow in 1880 to include collectively the diseases shared in nature by man and animals. Later WHO in 1959 defined that Zoonoses are those diseases and infections which are naturally transmitted between vertebrate animals and man.
- Zoonoses may be bacterial, viral, or parasitic, or may involve unconventional agents.
- Zoonotic transmission can occur in any context in which there is companionistic (pets), economic (farming, etc.), predatory (hunting, butchering or consuming wild game) or research contact with animals.
- Diseases which “spillover” from animals to humans are referred to as zoonotic diseases, and represent more than 60% of emerging infectious diseases worldwide.
- The destruction of the natural environment, globalised trade and travel and industrialised food production systems have created numerous pathways for new pathogens to jump between animals and humans.
Role of bats in the spread of disease
- The scientific study has shown that the SARS-CoV2 virus that cause Covid-19 emerged in bats and there is a sense of fear that bats can carry more diseases that can be transmitted.
- Bats have a unique characteristic of being a natural reservoir for many pathogenic viruses such as Hendra, Nipah, Marburg, Ebola, and the coronaviruses that cause severe acute respiratory syndrome.
- Flying long-distance can result in the damage of cell contents and to avoid such damage bats have developed an immune system that protects them from harmful viruses. Despite being the reservoirs of the viruses, bats never fall sick.
- This immune system also enables them to live longer and age slower. They are the longest-lived mammals for their body size.
- Because of Covid-19, we have come across the fact that bats can transmit viruses to humans. But this transmission of viruses from the natural hosts (bats) to the novel hosts (humans) is a rare event and can only take place by increased contact between bats and humans.
- Over the period of time, humans have cut the forests for agriculture and development use. They have also sped up the mining process which destroys the homes of bats as they live in natural caves.
- This imbalance caused by humans leads the bats to change their homes and it makes them stressed. Thus, the risk of spillover of viruses increases.
- Scientists have concluded that this ecological imbalance has made bats move closer to human habitats and transmit the viruses they carry along with them.
- Many indigenous groups of people are dependent on nature and animals and they try to maintain the balance without any harm to both humans and animals. They understand the importance of giving space to all animals including bats.
- One example of this is the bat harvest festival of the Bomrr clan in Nagaland. They celebrate a festival in which they smoke a cave in which the bats live and when the bats start exiting, they kill them for consumption purposes. During this process, bats bite or scratch them but this does not lead to the outbreak of any harmful disease due to viruses.
- The National Centre for Biological Sciences (NCBS-TIFR) and the Centre of Department of Atomic Energy (DAE) are conducting research on how the Bomrr clan are immune to such viruses.
- They are also studying the microbial diversity of bats and serology to identify which part of diversity is potentially pathogenic.
- They have come to a finding that there is a genetic prevalence of bacteria and viruses in bats and they have also found that humans and bats have a common antibody response to certain viruses that is an indication of spillover.
- The NCBS is also trying to collect a series of genomes of bat viruses so that they can be prepared for any possible outbreak in the future.
Details of Increased Zoonotic Disease
- About 60 per cent of known infectious diseases in humans and 75 per cent of all emerging infectious diseases are zoonotic.
- Zoonosis or zoonotic disease is a disease that has passed into the human population from an animal source directly or through an intermediary species.
- Zoonotic infections can be bacterial, viral, or parasitic in nature, with animals playing a vital role in maintaining such infections.
- Examples of zoonoses include HIV-AIDS, Ebola, Lyme Disease, malaria, rabies, West Nile fever, and the current novel coronavirus disease (COVID-19) disease.
Anthropogenic factors and Zoonotic Diseases
The report identified seven anthropogenic driving factors leading to the emergence of zoonotic diseases:
- Increased demand for animal protein;
- Rise in intense and unsustainable farming;
- The increased use and exploitation of wildlife;
- Unsustainable utilisation of natural resources;
- Travel and transportation
- Changes in food supply chains
- The climate change crisis.
The growing demand for animal-derived food has encouraged the intensification and industrialisation of animal production, wherein a large number of genetically similar animals are bred in for higher productivity and disease resistance.
- Intensive farm settings cause them to be raised in close proximity to each other, in less ideal conditions characterised by limited biosecurity and animal husbandry, poor waste management and use of antimicrobials as substitute for these conditions. This makes them more vulnerable to infections, which can further lead to emergence of zoonotic diseases.
- Loss of forest cover for agricultural purposes such as growing of soy, used as a key constituent of animal feed, is also influencing the emergence of zoonotic diseases by increasing human access to wildlife.
- High use of antimicrobials in such farm settings is also contributing to the burden of antimicrobial resistance (AMR), which itself is a chronic pandemic of high cumulative damage threating public global public health.
- The increased use and exploitation of wildlife can bring humans in closer contact with wild animals, thus increasing the risk of zoonotic disease emergence.
Views of Chiropterologists (those who study bats) on Villainizing bats
- Human activities and encroaching upon wildlife habitats put us at risk of encountering new viruses. We need to modify human practices to prevent the emergence of new pathogens.
- The exact origin of SARS-CoV-2 is still unknown and it is premature to blame bats or any other animal for the pandemic.
- Killing bats and destroying their habitats can be more harmful as this can lead to bats spreading out their habitat.
- We should remember that all wild animals harbour viruses and it is very biased and unfair to point fingers only at bats.
- If we keep destroying habitats, there are chances of the spread of other viruses from other animals to humans.
- The researchers and conservationists highlight that bats perform vital ecosystem services such as pollination and pest control and provide intangible economic benefits.
- They also clarify that the bat coronaviruses (BtCoV) found in two species of Indian bats (in a recent Indian Council of Medical Research study) are not the same as SARS-CoV-2 and cannot cause COVID-19.
-Source: The Hindu