Mosquitoes living in Brazil’s Atlantic Forest are showing a growing preference for human blood, a shift scientists say is linked to the ongoing loss of biodiversity and wildlife habitat.

The Atlantic Forest once stretched along much of Brazil’s coastline and supported hundreds of species of birds, mammals, reptiles, amphibians, and fish. Today, only about one-third of its original area remains. As human development displaces wildlife, mosquitoes are losing traditional animal hosts and increasingly turning to people for blood meals.

A new study published in Frontiers in Ecology and Evolution analyzed mosquitoes collected from two natural reserves in Rio de Janeiro state. Using DNA sequencing, researchers identified the source of blood meals in captured female mosquitoes. Of the identifiable samples, most came from humans, with far fewer from birds, amphibians, rodents, or other animals.

Researchers warn that this shift toward humans could elevate the risk of disease transmission. Mosquitoes in the region are known to spread viruses such as dengue, Zika, yellow fever, chikungunya, Mayaro, and Sabiá, all of which can cause serious illness.

Scientists emphasize that mosquito feeding behavior is influenced not only by species preference but also by host availability and proximity. As wildlife disappears and human presence expands, mosquitoes are more likely to encounter and feed on people.

Understanding which hosts mosquitoes prefer is critical for assessing disease risk and designing targeted surveillance and prevention strategies. Researchers say continued monitoring can support better mosquito control efforts and highlight the importance of protecting ecosystem balance as part of long-term public health protection.