Mosquitoes are increasingly thirsty for human blood

As human presence drives animals from their habitats, mosquitoes that once They fed on a wide variety of hosts could be finding new human targets to quench their bloodlust, according to a new study from the Oswaldo Cruz Institute and the Federal University of Rio de Janeiro, both in Brazil, published in Frontiers in Ecology and Evolution.

Stretching along the Brazilian coast, the Atlantic Forest is home to hundreds of species of birds, amphibians, reptiles, mammals and fish. However, due to human expansion, only about a third of the rainforest’s original surface remains intact. “Here we demonstrate that the mosquito species that we capture in the remnants of the Atlantic Forest have a clear preference for feeding on humans“writes the main author, Dr. Jeronimo Alencar, biologist at the Oswaldo Cruz Institute in Rio de Janeiro.

“This is crucial because, in an environment like the Atlantic Forest, with a great diversity of possible vertebrate hoststhe preference for humans significantly increases the risk of pathogen transmission,” adds co-author Dr. Sergio Machado, a researcher who studies microbiology and immunology at the Federal University of Rio de Janeiro.

For their study, the researchers used light traps to capture mosquitoes in the Sítio Recanto Reserve and the Guapiacu River Ecological Reserve, two natural reserves in the state of Rio de Janeiro. In the laboratory, swollen female mosquitoes were separated for analysis. The researchers extracted DNA from the blood and used DNA sequencing. DNA to analyze a specific gene that functions as a unique ‘barcode’ for each vertebrate species. By comparing the barcodes found in the blood with a database, the researchers were able to determine which animal the mosquito had fed on.

Of a total of 1,714 mosquitoes capturedbelonging to 52 species, 145 females They were engorged with blood. The blood could be identified consumed by 24 of these mosquitoeswhich came from 18 humansan amphibian, six birds, a canid and a mouse.

Some blood ingestions came from multiple sources: ingestion of blood from a mosquito identified as Cq. Venezuelensis was composed of amphibian and human blood. Mosquitoes belonging to the species Cq. Fasciolata had fed on both a rodent and a bird, as well as a bird and a human, respectively. Thus, according to the work, although some species of mosquitoes may have innate preferences, the availability and proximity of the host are extremely influential factors.

As the Atlantic Forest declines due to deforestation and humans continue to advance into formerly forested areas, many plants and animals disappear. As a result, mosquitoes They change their habits and habitats and become closer to humans. “With fewer natural options available, mosquitoes are forced to look for new, alternative blood sources. They end up feeding more on humans out of convenience, since we are the most frequent host in these areas,” explains Machado.

Bites are more than just an itch. In the study regions, mosquitoes transmit various virusesas yellow fever, dengue, zika, mayaro, sabiá and chikungunyawhich cause diseases that seriously threaten human health and can have long-term adverse consequences. Investigating the feeding behavior of mosquitoes is essential to understand the ecological and epidemiological dynamics of pathogens that they transmit, the researchers said.

The relatively low rate of engorged mosquitoes (just under 7%), as well as the low percentage of cases in which blood ingestion could be identified (around 38%), highlight the need for studies with a larger database. These studies also They should use more appropriate methods to identify mixed blood intake and thus determine all food sources.

The study may already contribute to the development of more effective policies and strategies to control disease-carrying mosquitoes and help predict and prevent future outbreaks.

“Knowing that mosquitoes in an area have a strong preference for humans serves as an alert about the risk of transmission,” warns Machado. This allows specific surveillance and prevention actions. Therefore, according to the work, in the long term, this could lead to control strategies that consider the balance of the ecosystem.