Bats as Viral Resevoirs

Bats’ unique immune systems may amplify the lethality of zoonotic viruses passed to other animals and humans, a new UC Berkeley study finds. Bats seemed to have developed an important adaptation related to flight that allows them to avoid inflammation. Because the metabolism of bats in flight operates as twice the speed for similarly sized rodents who don’t fly, one would expect the life span of bats to be very short. In general the faster the metabolism in small animals, the shorter the life span due to the accumulation of free radicals and other malign molecular detritus. Yet Bats can live as long as 40 years where similar sized rodents are good for just a couple of years. The same quirk of bat physiology that enables them to clean up free radicals also enables them to avoid inflammation. This adaptation in turn allows the bat immune systems to run at much more aggressive tempo than seen in any other mammals. Humans for example would suffer debilitating inflammation if our immune systems ran at the same pace that bats’ systems run.  Cara Brook, a postdoctoral Miller Fellow at UC Berkeley and the first author of the study noted, “Our immune system would generate widespread inflammation if attempting this same antiviral strategy. But bats appear uniquely suited to avoiding the threat of immunopathology.”

Brook and her colleagues believe that viruses confronted with the bats’ intense immune response are triggered into a much more rapid replication cycle. The accelerated replication rate carries through the zoonotic transition. Thus even when the viruses jump to an intermediate host like civets in the case of SARS; Camels in the case of MERS;  chimpanzees and gorillas with Ebola; pigs and Nipah; horses with Hendra; and African green monkeys with Marburg,  the viruses still exhibit intense lethality after making the final jump into humans.

~~ Pete Dailey

Sources:

eLife 2020;9:e48401cited in Sanders, Robert. Berkeley News, “Corona Virus Outbreak Raises Question: Why are Bat Viruses So Deadly?” 10 February, 2020. https://news.berkeley.edu/2020/02/10/coronavirus-outbreak-raises-question-why-are-bat-viruses-so-deadly/fbclid=IwAR3bHR5WODiHaDHArSuTyp7E0Hg1y2ANkFm4ypRUboWwuBbM_BtQyd_hqVM