Why bats carry deadly virus but don't get sick

2020-01-30
 What is the most successful mammal and how would you answer it? From the perspective of the development of a single species, it is undoubtedly our own, but if you only compare the number of individual species, the answer may surprise you. It is neither human nor livestock, not even mice, but nighttime Those little things flying in the sky-bats.

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Their wings are made up of five fingers.

As the only mammal that rushed into the sky, bats just tore a hole in the sky of bird hegemony and occupied the night, becoming the fourth type of flying creatures after insects, pterosaurs and birds. Just as the Germans attacked Paris on August 30, 1914, people saw the huge advantages shown in the first strategic bombing in history, and they had a huge advantage in flying in living things. Bats rely on rich and nutritious flying insects The food is extremely moist. Although the pterodactyl is only a small branch in the biological classification, it monopolizes one fifth of the mammals and is very prosperous.

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Humans and bats are heterogeneous
 
But why are many plagues related to bats? Why haven't bats been killed by these viruses? Is it true that only bats have many viruses?
 
It's true that there are many more viruses from bats than from other animals. It's said that some of the bat's "unique skills" are that these characteristics make them a successful species, and also that these characteristics make bats become "poisonous insects" of captive viruses.

Bats are mobile "virus banks." More than 140 viruses have been found in bats, of which more than 60 are zoonotic viruses, and some of them are still unknown.
Numerous "killing" viruses such as SARS virus, rabies virus, and Ebola virus can be found in bats.
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First of all, we need to know a biological common sense. For a constant temperature animal, the larger the body, the longer the life expectancy, and the slower the heartbeat. For example, the heartbeat of an elephant is only 26 times per minute, and the average life expectancy is 60 years. The heartbeat of a blue whale can be as low as 2 times per minute (when diving), and the average life expectancy is 80 years old. Moreover, the heartbeat of a mouse can reach 500 times per minute, and the lifespan is only limited 3 years.


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This is because the small body will dissipate heat very quickly, so it needs a higher metabolic rate to maintain body temperature. The same is true for bats. Because they need to fly, energy consumption and body temperature are more challenging, so they need a stronger metabolic rate. The heart rate of bats can be as high as 800 ~ 1000 times per minute.
 
So the question is, what is the life expectancy of a bat about the size of a mouse? If it is calculated according to the rules ... however, it must be less than 3 years ...

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I believe you have noticed the fact that the average age of humans is 70 years old, but the average heartbeat is rarely less than 60 times per minute. This is because humans are a heterogeneous species; likewise, bats are a heterogeneous species. They have Unreasonably long average life-30 years!
 
What is going on? In a genetic mutation about 5 million years ago, bats gained the ability to repair genes, so their somatic cells can divide far beyond the limits of ordinary animals (human somatic cells usually divide 50 to 100 times).

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The strongest immunity makes the biggest poisonous insect

This is great. Now that you are not afraid of cell division and wear,so nonstop manufacturing? our immune system has time to respond. So the bat raised his temperature to 40 ° C, desperately burned calories, and adjusted his immune system to a "normally on mode".
 
You know, the full-open mode of our human immune system is "fever". This is to destroy the stressful state of most pathogens with high temperature. If the body is in such high temperature for a long time, the body can't stand it. One start-up time, it starts to work after being activated by the pathogen, Sometimes some violent pathogens can be immune to us Before the system can react, it will knock people down.

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Look at other bats, life is fever, fever is life, no problem at all! So they have the most active and powerful immune system in mammals, and even very powerful bacterial viruses can't help them. For example, in North America, rabies has been completely eliminated from cats and dogs, but occasionally rabies patients are caused by bat bites (fortunately, Chinese bats do not bite people).

However, a strong immune system does not mean that all pathogens can be eliminated, but that these bacteria are suppressed. Then you can imagine that under the powerful suppression of the bat's immune system, the germs will be subjected to extraordinary "exercise" and become more "strong" and "evil" under strong selection pressure.
 
This is similar to the "super bacteria" born from the abuse of antibiotics. The bat's body has become a container for culturing "super pathogens". The bat itself is fine, but it infects other animals. Bats also fly around, and the ability to spread germs is much stronger than that of ordinary animals.

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And more importantly, bats are mammals. Generally speaking, the farther the evolutionary kinship between living things is, the less likely it is to be susceptible to diseases. For example, although birds are thermostatic animals, they are rarely offspring because they are offspring of dinosaurs Can be transmitted from birds to humans (avian flu). Relatively speaking, the germs in bats are quite deadly. It only needs a small mutation to be transmitted to other wild animals, and then to the crowd through the wild animal market.

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The importance of bats

There is one thing on bat that can be used as medicine, that is, its defecation. It has a nice name - night sand

In the 1980s and 1990s, we often saw bats. Every summer night, it always hovers around the streetlights, passing silently, never disturbing people's lives. Old people often say that it is eating mosquitoes. Indeed, bats are not only important controllers of nocturnal pests, but also important pollinators of plants. A 20g bat can eat 200 to 1000 insects a night, which is an important guard of ecological balance. To this end, 2011 was designated as the International Year of bats by the United Nations Environment Programme to promote the benefits of bats to the ecosystem.

As an auspicious thing in China since ancient times, why is it difficult to see it today? In fact, there are many reasons for the declining number of bats. The main reasons are the destruction of their habitats, human intrusion and hibernation of hibernation places. Today, about half of bats are in danger of survival and have become an endangered species.



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