Decreasing biodiversity, particularly in tropical rainforests, has a direct impact on the prevalence of viruses, according to a study led by the Leibniz Institute for Zoo and Wildlife Research.
Published in the journal eLife, the research demonstrates that rainforest destruction leads to reduced diversity in mosquito species. This paves the way for more resilient mosquito species – and the viruses they carry – to become dominant.
The researchers set out to investigate how environmental changes, biodiversity loss, and the spread of pathogens may be connected.
The study was led by Professor Sandra Junglen, leader of the Ecology and Evolution of Arboviruses research group at Charité’s Institute of Virology.
The research team executed their study in and around Taï National Park in Côte d’Ivoire, encompassing a diverse array of land uses, from untouched rainforests to human settlements.
“We identified the species of mosquitoes we had caught and tested them for viral infections,” explained study first author Kyra Hermanns.
“Then we looked at how the composition of mosquito species differs across the different land use types, where certain viruses are present, and how prevalent they are.”
In a healthy ecosystem such as a rainforest, many different viruses are present due to the wide variety of animal species – which act as hosts.
According to Junglen, the team identified 49 virus species, with the majority found in undisturbed habitats. However, certain mosquito species adapted efficiently to cleared areas, bringing along their respective viruses.
“Most of the 49 different virus species were relatively rare in the areas studied. However, nine of them were commonly found in multiple habitats, with the prevalence of five virus species increasing in habitats that had been disturbed and reaching the highest figures in human settlements,” said Junglen.
“This means that the clearing of tropical rainforests causes a decrease in the diversity of mosquito species, which changes the composition of host types. Some resilient mosquito species have multiplied very successfully in the cleared areas, bringing their viruses with them,” explained the researchers.
The composition of a given community of species has a direct effect on the prevalence of viruses: “If one host species is very abundant, it is easier for viruses to spread,” said Junglen.
“All of the viruses we found to be more common were demonstrated to be present in a certain mosquito species.”
“The viruses belong to different families and have different properties. That means we were able to show for the first time that the spread of the viruses is attributable not to a close genetic relationship, but to the characteristics of their hosts – especially those mosquito species that adapt well to changing environmental conditions in habitats that have been disturbed.”
Although the discovered viruses currently pose no threat to humans, the study sheds light on the dynamics of infectious diseases.
“Our study makes clear just how important biodiversity is, and that decreasing biodiversity makes it easier for certain viruses to thrive because it causes their hosts to become more abundant,” said Junglen.
“Previously, these kinds of processes were studied almost exclusively using individual pathogens and individual hosts. Now we have a more complete picture that we can use for further research.”
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