Munich (ots) – Coronaviruses from wild bat populations have already caused major human disease outbreaks three times in the past 20 years: SARS in 2002, MERS in 2012 and COVID-19. The latter triggered a global pandemic, from the consequences of which humanity has still not fully recovered. This has also caused increased attention to infectious diseases whose origins lie in the animal kingdom – so-called zoonoses.
- LMU researchers show that the more an ecosystem is influenced by humans, the more bats in it are infected with corona viruses.
- This increases the likelihood of new zoonoses and pandemics.
- For the risk assessment and prevention of future zoonoses, especially in areas that are heavily influenced by humans, the infection rates in wild animals should also be taken into account.
One thing is now clear: the probability of so-called spillover events, in which pathogens spread from animals to humans, increases the more humans invade the wilderness. Various factors play a role in this. For example, how much human invasions into intact ecosystems increase contact rates between humans and potentially infected species, or how easily a virus can adapt to a new host.
dr Vera Warmuth and Prof. Dr. Dirk Metzler from the Department of Evolutionary Genetics at the LMU, together with the bat ecologist Dr. Veronica Zamora-Gutierrez at CIIDIR Durango in Mexico demonstrated another connection that is relevant: The study was able to clearly demonstrate that bats in habitats disturbed (by humans) are more frequently infected with coronaviruses than those in undisturbed habitats.
To do this, the researchers used a meta-analysis to collect and statistically analyze information on infection rates in bats from all over the world. Data from over 26,000 bats from over 300 species were included in the evaluation and combined with data on land cover and land use.
“Many forms of land use mean a loss of important resources for wild animals; in the case of bats, for example, hunting or roosting places,” says Vera Warmuth. It has been shown several times that such a loss of resources can lead to chronic stress for wild animals. If bats find no places to sleep or less food due to human intervention, the associated chronic stress can lead to a weakening of the immune system.
“The negative effects of chronic stress on the mammalian immune system are well known. Our results clearly show that animals in disturbed ecosystems are more likely to be infected. The more an area is affected by humans, the more coronaviruses are found in those living there bats,” says Warmuth.
Three forms of land use stand out in particular: agriculture, deforestation and the extraction of mineral resources. According to the authors of the study, they represent the greatest stress factors for bat populations. They destroy or fragment forest habitats, the bats find less food in the form of insects due to the cultivation of monocultures and the use of pesticides and even lose their underground roosting places if mining is carried out.
Ecological stress therefore has a significant effect on the frequency of coronaviruses in a group of animals, which is of great importance as a virus reservoir in nature. “If we want to predict and limit the risk of possible zoonotic pathogens spreading, it is necessary, according to our findings, to also monitor their frequency in wild animal populations. Especially if human pressure on ecosystems continues to increase,” says Metzler. “The models also point to a handful of regions, particularly in the eastern United States and India, where increased surveillance may be particularly important.”
Contact
Dr. Vera Warmuth
Department of Biology II
Department of Evolutionary Biology
Tel: +49 (0)89 / 2180-74142
Email: warmuth@bio.lmu.de
publication
Vera M. Warmuth, Dirk Metzler, Veronica Zamora-Gutierrez; Human disturbance increases coronavirus prevalence in bats. Science Advances, 2023
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