Bats May Hold Genetic Key

With the pandemic far from over, scientists are already looking for the source of the next one. Modern commerce and travel make the most isolated habitat ground zero for the next lethal virus to strike humanity. This is the reason Brazilian researchers are in the dense rainforest looking for bats. Bats are thought to be a vector in several lethal viral epidemics, iincluding COVID-19. Of all mammal vectors, primates, rodents, carnivores and ungulates, viruses found in bats tend to be the most lethal to humans. For example the Hendra virus, first identified in 1994 near Brisbane, Australia, was found in fruit bats that transmitted the disease to horses, which in turn infected humans. This virus is highly lethal, killing 75% of horses it infects, and 60% of humans.

Australian grey-headed, credit: A. Ruzicka

Another disturbing fact is that habitat destruction caused by man is responsible for bats living in areas close to settlements. This is what happened in Hendra, Australia where destruction of flowering eucalyptus trees drove fruit bats (Pteropus) [photo] closer to residences and farms where they infected horses. Fortunately, though highly lethal, Hendra virus infections are rare. Habitat destruction also contributed to the outbreak of the Nipah virus in Bangladesh which causes severe encephalitis in humans. Fruit bats looking for food moved into urban areas. They spread the virus by licking date palm sap from collection barrels. Fearful humans have taken to attacking bat colonies, but that only makes the risks of transmission worse. An investigation by the U.S. Centers for Disease Control and Prevention (CDC) and Ugandan health authorities found that after a mining operation attempted to exterminate bats from a cave in Uganda, the remaining bats exhibited higher infection levels of Marburg virus. This led to Uganda’s most severe outbreak of Marburg hemorrhagic fever in 2012. It is obvious from these and similar zoonotic events that bats host virus infections well, to which humans succumb in great numbers. Why?

That is the question the Brazilian bat researchers are hoping to answer by collecting bat tissue samples for genetic study from bats living in an urban park. Flying places great stress on a relatively small body, so bats generate extremely high metabolic rates--as much as 16 times resting rate--without apparent cell damage. Some bat species live for thirty years. Scientists theorize that along with the development of flight capability, bats evolved immune systems that are highly efficient and selective. Two mechanisms suggested for this enhanced capability are rapid DNA repair and inflammatory response suppression.

Genetic coding may hold to the key to their secret of bat resistance to some of the nastiest pathogens on the planet--COVID-19, SARS, MERS, Ebola, Nipah, Hendra and Marburg viruses. For now, the best defense is to keep bats away from human interaction. However, tropical rainforest deforestation is increasing the contact between host colonies and humans. Replacing destroyed habitat is an effective means of keeping bats to themselves. India is among the most likely places in the world for a “spillover” event to occur, due to high human population density and increasing human and livestock incursion into its dense forests teeming with wildlife.  Bat phobia is counterproductive since bats are valuable members of a balanced ecosystem, providing valuable insect control, seed dispersal, and pollination services. The fact is that bats are a highly successful organism with more the 1400 species flying around every continent except Antarctica. Man is disrupting nature's balance, NOT bats.