In Brazil's shrinking Atlantic Forest, deforestation is causing mosquitoes to increasingly feed on humans, heightening the risk of diseases like dengue and Zika. A new study reveals that out of identified blood meals, most came from people rather than wildlife. This adaptation underscores how habitat loss alters disease transmission patterns.
The Atlantic Forest along Brazil's coastline, once a biodiversity hotspot, has dwindled to about one-third of its original extent due to human development. As wildlife diminishes and settlements encroach, mosquitoes that previously fed on diverse animals are turning to humans as a primary blood source, according to research published in Frontiers in Ecology and Evolution.
Scientists from the Oswaldo Cruz Institute and the Federal University of Rio de Janeiro conducted the study in two reserves: Sítio Recanto Preservar and the Guapiacu River Ecological Reserve, both in Rio de Janeiro state. They deployed light traps to capture 1,714 mosquitoes across 52 species. Of these, 145 females had recently fed, and DNA analysis identified blood sources in 24 cases: 18 from humans, six from birds, one from an amphibian, one from a canid, and one from a mouse.
Some mosquitoes showed mixed feeding habits. For instance, one Cq. venezuelensis specimen had blood from both an amphibian and a human, while Cq. fasciolata included combinations like rodent and bird, or bird and human.
"Here we show that the mosquito species we captured in remnants of the Atlantic Forest have a clear preference for feeding on humans," said senior author Dr. Jeronimo Alencar, a biologist at the Oswaldo Cruz Institute.
Co-author Dr. Sergio Machado, a microbiology researcher, added: "This is crucial because, in an environment like the Atlantic Forest with a great diversity of potential vertebrate hosts, a preference for humans significantly enhances the risk of pathogen transmission."
Deforestation forces mosquitoes closer to human habitats, where people become the most accessible hosts. This shift amplifies the spread of viruses including yellow fever, dengue, Zika, Mayaro, Sabiá, and chikungunya, which can cause severe health issues.
The study notes limitations: fewer than 7% of mosquitoes had detectable blood meals, and sources were identified in only 38% of those. Larger investigations are needed, but the findings can inform targeted mosquito control and outbreak surveillance. "Knowing that mosquitoes in an area have a strong preference for humans serves as an alert for transmission risk," Machado said. Alencar emphasized: "This allows for targeted surveillance and prevention actions."
By highlighting ecosystem imbalances, the research calls for strategies that preserve forests to mitigate disease risks.
