[ad_1]
Let’s start at the line of hit: bats didn’t give us the last coronavirus. Nor were their notorious cousins SARS-1 or MERS, or even the Ebola virus, transmitted from bats to humans. So what happened?
A distant relative of the current coronavirus, SARS-CoV-2, was isolated from a bat in China. Genetic analyzes that looked for similarities between the virus in the bat and SARS-CoV-2, and took into account the theoretical rate at which the virus mutates, estimated that the two viruses separated between five and 50 years ago. In other words, one possibility is that about five years ago, the bat coronavirus managed to infect a different animal; we don’t know which one right now. In the next animal, the coronavirus lived and mutated during those five years, and one day it infected a human for the first time. There are also other hypotheses.
Science does not yet know where the coronavirus lurked in recent years, or when it became dangerous to people, or when the first person became infected, nor do we know which animal infected that first human. The only thing that science knows for sure is that the coronavirus isolated from the Chinese bat cannot have infected humans and is not dangerous to them.
This fact was published two months ago, based on the genetic sequences of the bat and human viruses. This is also true for SARS, MERS, and Ebola: Despite repeated efforts to locate these viruses in bats, all the researchers found were similar viruses, or evidence of prior exposure that does not mean they carried the virus. routinely and certainly not that they passed it on to humans, despite reports that appeared in the general press (including in the Hebrew edition of Haaretz on April 19).
Bat from hell
Why do bats have such a bad press in relation to viruses? In recent years, there have been increasingly strident claims that bats carry zoonotic viruses, which can infect humans. But there are serious scientists who disagree with this and argue that bats are no different than other mammals in the number of zoonotic viruses they carry, certainly considering the large number of species in the bat family. About a fifth of all mammals in the world are bats.
There are several quirky features that make them “suspicious” when it comes to viruses. Their ability to fly, their presence in all parts of the world, their large colonies and the overcrowding in which they live; their long lives; and their proximity to humans makes them apparently apt to transmit disease.
Related Posts
The fact that they are mammals increases the possibility that they are transmitters. That’s why searching for new viruses in bats has become almost a fad among researchers; and the deeper the search, the more likely something is to be found.
Furthermore, the cumulative findings show that the bats’ immune system is unique among mammals and is adept at treating viruses. This immune system allows bats to defend themselves against viruses, including deadly ones, through a moderate inflammatory response that leads to immunity. As a result, many studies find antibodies in bats, proof that they have been exposed to viruses, without finding the virus itself.
Without the live virus itself, the bat cannot be a carrier and certainly cannot be a transmitter. This means that the important link in the chain of zoonotic transmission to humans is still missing.
Eating a bat when it is sick can cause infection, just like eating any other sick animal, and it is not recommended. As a general rule, to reduce the possibility of zoonotic transmission of viruses from bats or any other animal, it is better to eat them infrequently and, in general, to minimize encounters with them; to allow them to live in their natural environments and stop invading their habitats.
It is interesting to note that bats’ amazing immune systems apparently evolved to support their unusual way of life. Bats live longer than almost any other mammal. In 2006, a Brandt’s bat (Myotis brandtii), weighing just 7 grams and about the size of his finger, was recaptured after scientists in Siberia tagged it 41 years earlier. A mouse of similar size would not live more than two years. Such extreme longevity requires an optimal immune system.
The ability of bats to fly, unique among mammals, appears to have also contributed to the development of their immune systems. In our studies we have found that small bats weighing no more than 30 grams can fly a distance of more than 250 kilometers in one night. Energy needs and accelerated metabolism during flight are accompanied by oxidative damage, which requires an appropriate immune system. Some believe that this immune system is the reason why bats rarely develop cancer.
Also, a bat that comes out of its cave at night increases its body temperature by a few degrees in a minute. This elevated body temperature, which reaches 40 degrees Celsius or higher, apparently helps kill undesirable viruses and bacteria.
It is important to emphasize that our love for bats has not blinded us (bats are not blind, either, by the way). There are zoonotic viruses that are transmitted by bats such as Marburg, Hendra, Nipah, and bat rabies, none of which are found in Israel. Bat viruses must be given the respect they deserve, but there is no reason to attribute bats to viruses that are not theirs.
Professor Yovel and Dr. Weinberg teach in the zoology department of the Tel Aviv University faculty of life sciences.
[ad_2]
