The benefit of bats outweigh their viral risk

Tory Moore, UF/IFAS
Contributor

From Hollywood movies to Halloween celebrations, bats have a reputation as spooky, vile creatures to be avoided. The novel coronavirus has only deepened the disdain and fear some people hold toward bats around the world.

Although bats are associated with viruses like Ebola and rabies, and possibly, COVID-19, the nocturnal creatures benefit us in a myriad of ways which include controlling insects that spread diseases and damage crops, UF/IFAS wildlife experts say.

When left undisturbed in their wild habitats, bats pose very little risk to human health and provide many ecological benefits to humans. Many species of bats are pollinators, dispersing seeds of hundreds of species of fruit including mangos, bananas and guavas. Other bats are insectivores, eating millions of tons of insects in just one night.

“Recent estimates show bats save farmers, ranchers and gardeners billions of dollars each year by naturally controlling pests of agricultural crops,” Holly Ober, an UF/IFAS associate professor of wildlife ecology and conservation and an Extension specialist.

Bats consume a variety of mosquitoes, further benefiting human health by reducing the ability of mosquitoes to spread mosquito-borne diseases such as Zika, dengue, malaria and chikungunya.

Bats possess highly specialized immune systems that let them host viruses, including coronaviruses, without showing signs of illness.

“For many mammals, including humans, it is not the viral infection that leads to death, but the acute inflammatory response brought on by their immune systems,” said Samantha Wisely, UF/IFAS professor of wildlife ecology and conservation. “Bats can control the inflammatory responses of their immune system. So, while they may be infected, they do not show visible signs of disease.”

Scientists are studying bat immune systems to develop techniques to regulate the inflammatory response in humans to viruses like COVID-19.

Sometimes, bats carry zoonotic diseases, which can be transmitted between animals and humans. Since humans are not often exposed to wildlife diseases, we are susceptible to infection by those rare diseases, when we are exposed. This transmission is called a “spillover event” because the virus “spills over” from an animal host to a human host. Human-to-human transmission of such diseases can then lead to pandemics like we are experiencing now.

Scientists have shown that wildlife markets, trade in meat from wildlife, and illegal wildlife hunting cause spillover events. Public health and wildlife conservation organizations have called for tightening of restrictions on the bushmeat trade and the closing of all wildlife markets to prevent future spread of zoonotic diseases into humans.

Spillover events could become more common as wildlife habitat is destroyed, forcing wildlife into close contact with humans.
Deforestation and suburban sprawl can displace wildlife, including bats. Purposeful vandalism of caves or harvesting of trees used as bat roosts can force bats into closer proximity to humans, which is the phenomenon we want to avoid, according to Ober.
Displaced bats will be stressed due to their immediate need to find alternative sources of shelter.
When stressed, animals produce more virus, increasing the chances of disease transmission to humans. These viruses become a threat to humans only when the bats are stressed and in close proximity to humans.
“People would be far better served if they acted to protect the natural habitats bats need rather than harming those habitats and thereby forcing bats into poor-quality environments and closer to people,” Ober said.
The speculation that COVID-19 originated from bats has caused a persecution of bats worldwide in the name of protecting public health.
“This response is damaging and counterproductive,” Ober said. “Culling bats creates far more problems for human health than it solves.”
To help the bat population in your own backyard, provide them with a roosting habitat, a place where they can sleep during the day. Many bats sleep in groups in chambers within tree trunks. To preserve these habitats, retain or create trees with cavities, avoid trimming dead fronds from palm trees and install bat houses.
“Bats have long been subject to human disliking because they are unusual and they are active at night,” Ober said. “We have a tendency to distrust things we can’t see and don’t understand well.”
Educating others about the benefits bats provide and helping dispel rumors about bats will benefit both bats and humans.
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