Bats are infected with many dangerous viruses such as rabies, SARS, and Ebola. While these viruses can be lethal to other mammals, bats seem to be unaffected. In fact, they can live for up to 30 years under normal conditions. So what is protecting them from these dangerous diseases?
For a long time, bats have been viewed as a primary cause of disease outbreaks, as they themselves are reservoirs for a large number of viruses.
In 2017, an infection spread to an entire herd of pigs on a farm in Guangdong Province, China. The livestock suffered from severe diarrhea, and piglets died one after another. At least 24,000 pigs perished. According to the findings of a scientific team published for the first time in a British scientific journal, the acute diarrhea syndrome that led to the pigs’ deaths was caused by a new virus derived from coronaviruses found in bats.
Years later, humanity was officially attacked by another type of coronavirus, which unfortunately also has a close relationship with bats. According to a scientific report, 96% of the genetic sequence of the new coronavirus, or its total genetic information, matches that of the coronavirus found in the horseshoe bat species residing in Yunnan Province, China.
The coronaviruses that caused SARS and the Middle East Respiratory Syndrome (MERS), discovered in 2012, also originated from bats. The Ebola virus, which has a mortality rate of up to 90% in humans, and the Nipah virus, with a mortality rate ranging from 40% to 75%, both stem from bats. As of 2016, 5,629 types of viruses, including non-pathogenic ones, were identified in bats.
Why are bats the source of so many diseases? It is due to their lifestyle and bodily functions.
The Relationship Between Viruses and Their Hosts
To answer this question, we first need to understand the relationship between viruses and their hosts. Each type of virus has evolved to infect specific species. This is why humans cannot be infected by plant viruses and why bees do not get the flu. However, viruses can sometimes evolve and jump to new, related hosts. Because the immune system of the new host has not developed specific antibodies to combat the virus, it can lead to the host’s death.
Each type of virus has evolved to infect specific species.
This is indeed bad news for viruses. An ideal host that viruses target has a stable resource for the virus to thrive and continue spreading, only living hosts can meet these two criteria. Therefore, successful viruses often do not evolve to kill their hosts.
The lethal effects of these viruses are often not directly caused by the pathogens but rather by the uncontrolled immune response of the host. Infections like Ebola or certain strains of influenza can overwhelm the host’s immune system. The body sends white blood cells, antibodies, and inflammatory molecules to eliminate the external invaders. However, if inflammation is too high, the attacked immune system can lead to severe tissue damage, resulting in infection and death.
The lethal effects of viruses are due to the uncontrolled immune response of the host.
Why Do Bats Get Infected with Dangerous Viruses but Not Die?
Unlike other mammals, bats have engaged in an evolutionary arms race with these viruses for millennia, and they have adapted to minimize self-harm mechanisms. Their immune system shows a very low inflammatory response, which is a remarkable adaptation.
The process of evolution has resulted in the loss of some genes related to the deployment of inflammatory molecules in bats. As a result, a controlled low-level inflammatory response allows bats to coexist with viruses. A low response does not mean that bats lack an immune system; rather, it is an effective immune response that does not overreact and lead to self-destruction. Even more impressively, bats can harbor these viruses for decades without any negative health consequences.
Bats have also developed an effective system for repairing damaged DNA.
Additionally, bats have developed an effective system for repairing damaged DNA, which also contributes to their longevity. Some bat species can live up to 40 years. Of course, bats are not entirely invulnerable to disease. Bat populations have been devastated by a fungal infection known as white-nose syndrome, which can disrupt their hibernation and damage wing tissue.
The Benefits of Bats to Their Ecosystem
While it can be said that bats are hosts for many viruses that can harm humans, the benefits they provide are also significant. Bats play a crucial role in the ecosystem by helping with pollination and seed dispersal, as well as consuming pests and insects.
Therefore, to protect these animals from harm and to safeguard humans from dangerous infectious diseases, we need to stop encroaching on bats’ habitats and ecosystems.
Bats play a crucial role in the ecosystem by helping with pollination and seed dispersal.
It is hoped that the conservation and continuous research of bat populations will allow scientists to better understand the unique immune system against viruses of these animals. And perhaps in the future, humanity will discover a new method of viral immunity.
