Scientists have found that the immunity of bats is stronger than that of humans. This explains why bats live much longer than other mammals of the same size, and also why their viruses are so dangerous to humans. The results of the study are published in the journal eLife.
Most of the worst outbreaks of viral diseases in recent years - SARS (SARS), MERS (Middle East Syndrome), Ebola and Marburg viruses, and, with a high degree of probability, the new Chinese coronavirus 2019-nCoV came from bats.
The results of the study showed that a viral infection triggers a fast and powerful immune response in bats, which, on the one hand, protects these animals, and on the other hand, an aggressive immune response forces the viruses to actively multiply and adapt.
This feature of the organism of bats makes them a unique reservoir of rapidly multiplying highly virulent viruses. Therefore, when these viruses are transmitted to mammals with weaker immune systems, such as humans, they are deadly.
"A rapid immune response protects bat cells from infection, although the virus continues to replicate without harm to the host. However, when a virus is transmitted, for example, to a person who does not have a similar antiviral defense mechanism, it provokes many complications," release from the University of California at Berkeley by Cara Brook, the first author of the study.
The virus could be transmitted to humans through food. It is believed that the source of the 2019-nCoV coronavirus infection was at a fish market in Wuhan, where large numbers of live animals were sold for gastronomic purposes. In addition, disturbance of the habitat usually causes stress in animals, which leads to an increased excretion of all physiological products containing the virus - saliva, urine and others.
The results were obtained by scientists during their work as part of the Bat One Health project, which studies the links between habitat disturbance in bats and the spread of their viruses to other animals and people. A monitoring program funded by DARPA, the US Defense Advanced Research Projects Agency, is currently being implemented in Madagascar, Bangladesh, Ghana and Australia.
"The heightened environmental threat to bats could increase the risk of zoonotic infections," says Brook.
“The bottom line is that bats are special when it comes to viruses,” says Mike Boots, professor of integrative biology at the University of California at Berkeley and one of the authors of the paper. Our work demonstrates that the immune system of bats can drive virulence."
As the only flying mammal, bats increase their metabolic rate in flight to twice that of similarly sized running rodents. As a rule, vigorous physical activity and high metabolic rates lead to more severe tissue damage due to the accumulation of reactive molecules, primarily free radicals. But bats seem to have developed physiological mechanisms to effectively release these destructive molecules. In parallel, their body gets rid of any inflammation caused by a variety of reasons, which may explain the unique lifespan of these animals.
Smaller mammals with a faster heart rate and metabolism generally have a shorter lifespan than larger animals with a slower heart rate and metabolism because high metabolism results in a faster release of damaging free radicals. But bats are unique in that their lifespan is much longer than that of other mammals of the same size. Some bats can live up to 40 years, while rodents of the same size can live for two to three years.