Bats: victims of slander
In a groundbreaking scientific article published in Biology Letters, an international team of biologists, virologists, and environmentalists, including Sébastien Puechmaille from the Montpellier Institute of Environmental Sciences (Isem), challenges the commonly held belief that bats, particularly those in Africa, are the source of a myriad of viruses harmful to humans. Contrary to popular belief, this in-depth review of published studies provides little substantial evidence, apart from the Marburg and Sosuga viruses, that African bat species serve as reservoirs or intermediate hosts for viruses that spread to humans and cause serious diseases.
The scientific community and the public have often been confronted with representations of bats as carriers of numerous dangerous viruses transmitted to humans. However, the research team, led by Natalie Weber, conducted an exhaustive and critical review of the available literature, focusing specifically on viruses detected in bats in Africa. They meticulously examined 162 articles published between 1978 and 2020 and, based on data from more than 80,000 individuals belonging to more than 167 bat species, no substantial evidence was found that any bat species other than the Egyptian fruit bat plays a central role in the transmission of viruses to humans in this region.
“The objective of our study was to provide a balanced and evidence-based assessment of the available knowledge regarding bat viruses and their relevance to the transmission of bat viruses to humans in Africa. After careful review and analysis, we found no compelling evidence to support the prevailing notion that bats harbor a large number of viruses that are transmitted to humans. On the contrary, our findings reveal only two bat-virus systems in which transmission is clearly documented," says Natalie Weber.
A more nuanced approach
The researchers systematically evaluated the available data and determined which bat species were sampled, how often and in which country, whether they were sampled in a lethal or non-lethal manner, what metadata was collected, and which viruses were detected using which methodology. The results of these analyses challenge not only the scientific community but also the general public's perception of bats, highlighting the importance of evidence-based understanding. DeeAnn Reeder, co-author of the study, notes that "the results underscore the need for a more nuanced and informed approach to public discourse on the role of wildlife in disease emergence." The authors therefore propose a framework to facilitate standardized assessment of virus hosts in the future and call for greater interdisciplinary collaboration in studies of bats and viruses.
This review also revealed that misidentification of bats and obsolete species assignments were common in published studies on viruses. Yet species identification is of great importance for follow-up investigations, particularly when a particular bat is established as the host of a virus of interest. Furthermore, bats are often considered a single entity, but it is crucial to recognize the substantial diversity within this group, which has diversified over tens of millions of years; Africa alone is home to no fewer than 324 different bat species.
“When examining the relationship between bat species and viruses, precise language is vital. Instead of making a general statement that ‘bats harbor the Marburg virus,’ it is more accurate to specify that ‘the Egyptian fruit bat, a specific species of bat, harbors the Marburg virus.’ This succinct approach preserves accuracy and avoids mistakenly associating all bat species with the Marburg virus,"explains Sébastien Puechmaille, co-author of the study and researcher at the Institute of Evolutionary Sciences in Montpellier.
Careful communication
As emerging infectious diseases continue to cause global concern, researchers hope that their work will contribute to a better understanding of the complex dynamics between wildlife, particularly bats, and human health. Their study also raises concerns about the impact of repeated communication of research linking bats to viruses, based on missing evidence, on public perception of bats, as well as on human-bat conflicts and bat conservation efforts.
“Fear and active persecution of bats are increasing significantly, and populations are likely to decline across Africa. Careful, science-based communication of the findings and a balance between potential risks and benefits will be essential to achieving coexistence between humans and bats in our changing world,"says Dina Dechmann, co-author of the study. The implications of this research extend beyond Africa, encouraging a more thoughtful and evidence-based approach to the study of zoonotic diseases worldwide.