A surprising phenomenon is being observed in mosquitoes in Brazil. As the Atlantic Forest loses ground, these insects, which previously took their meals from a great diversity of animals, are now turning more frequently to humans.
In Brazil's coastal regions, the Atlantic Forest once harbored exceptional biodiversity, with unique birds, amphibians, and mammals. Today, nearly two-thirds of this forest have disappeared, replaced by human activities. This transformation of the landscape drastically reduces the number of available animals. A study published in
Frontiers in Ecology and Evolution indicates that mosquitoes living in the remaining forest fragments are compensating for this loss by biting people more frequently.
To better understand this phenomenon, scientists installed light traps in two protected areas in the state of Rio de Janeiro. They collected female mosquitoes engorged with blood and then analyzed the DNA present in this blood to identify the origin of the meal. Among the identified meals, the majority came from humans, confirming a clear trend.
According to the study's authors, this behavior is not necessarily linked to an innate preference of the insects for human blood. Limited access to traditional animal hosts, such as birds or amphibians, plays a central role. With fewer options available, mosquitoes fall back on the most abundant and easily accessible source, namely the human populations living nearby.
This change in diet has significant consequences for public health. In these regions, mosquitoes are vectors for many viruses, such as those causing yellow fever, dengue, or Zika. Greater proximity to humans multiplies opportunities for transmitting these diseases, which can threaten local communities.
The results of this research can guide prevention efforts. Knowing that mosquitoes in a given area primarily target humans allows for the implementation of appropriate surveillance and more effective control measures. In the long term, this could also encourage strategies that take ecosystem balance into account to reduce health risks.
This study highlights the need for further research to better understand the feeding habits of mosquitoes, particularly when they feed on several different hosts. More comprehensive data would help refine models of disease spread.