Mosquito Feeding Shifts in Brazil Raise Human Disease Risk

Brazil's Atlantic Forest, a biodiversity hotspot, stretches along the country's eastern coastline. It originally spanned more than 1.3 million km² but now retains only about 29% of its coverage due to human activities like agriculture, horse breeding, and residential expansion. This biome supports approximately 850 bird species, 370 amphibians, 200 reptiles, 270 mammals, and 350 fishes, sustaining diverse mosquito populations through abundant vertebrate hosts, however a recent Frontiers in Ecology and Evolution study reveals that as human encroach on the forest mosquitoes are increasingly preferring human blood over wild hosts, heightening disease transmission risks.

Researchers led by Jeronimo Alencar at the Oswaldo Cruz Institute captured 1,714 mosquitoes from 52 species using light traps at two Rio de Janeiro reserves: Sítio Recanto Preservar and Guapiacu River Ecological Reserve. They analyzed blood meals from 145 engorged females by extracting DNA from the blood and using sequencing to analyze a specific gene that functions as a unique ‘barcode’ for each vertebrate species. By comparing barcodes found in the blood to a database, the researchers could determine which animal the mosquito had fed on.

Of 24 identifiable meals, 18 came from humans, alongside one amphibian, six birds, one canid, and one mouse. Mixed feeds included Cq. venezuelensis with amphibian and human blood, and Cq. fasciolata with rodent-bird or bird-human combinations.

Identifying food sources helps investigate mosquito feeding patterns, life history traits, host search factors, survival, and reproductive success, as prior studies note. Host availability strongly influences blood feeding, and understanding these habits clarifies mosquitoes' roles as pathogen vectors and their ecological interactions. "Here we show that the mosquito species we captured in remnants of the Atlantic Forest have a clear preference for feeding on humans," stated Dr. Alencar. Co-author Sergio Machado 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 drives mosquitoes closer to humans, reducing natural options and favoring convenient human hosts. "With fewer natural options available, mosquitoes are forced to seek new, alternative blood sources. They end up feeding more on humans out of convenience, as we are the most prevalent host in these areas," Machado explained.

"Knowing that mosquitoes in an area have a strong preference for humans serves as an alert for transmission risk," Machado added enabling targeted surveillance and prevention actions.