Deforestation forces brazilian mosquitoes to target humans as wildlife disappears

A troubling shift is occurring in Brazil’s Atlantic Forest, where mosquitoes are increasingly feeding on human blood as deforestation eliminates their traditional wildlife hosts. New research from one of the world’s most threatened biodiversity hotspots reveals how habitat destruction is creating unexpected consequences for human health.

Scientists from the Oswaldo Cruz Institute analyzed blood samples from 145 female mosquitoes collected across two Atlantic Forest reserves in Rio de Janeiro state. Their findings were stark: three-quarters of the mosquitoes had fed on humans rather than wild animals. The remaining blood meals came from birds, amphibians, and small mammals—a dramatic departure from what would be expected in a healthy ecosystem.

“Mosquitoes in the Atlantic Forest have a clear preference for feeding on humans,” said senior researcher Jeronimo Alencar. This preference isn’t natural behavior but rather a response to environmental crisis. The Atlantic Forest, once covering vast swaths of Brazil’s coast, has been reduced to less than one-third of its original size due to deforestation and development.

The implications extend beyond mere inconvenience. Several mosquitoes showed evidence of feeding on multiple species—including human-bird and human-amphibian combinations—raising serious concerns about disease transmission. As wild animal populations decline and flee degraded habitats, mosquitoes are forced to seek new blood sources, increasingly bringing them into contact with human communities and creating new pathways for pathogens to spread between species.