Without forests, mosquitoes turn to human blood
If you are someone who just mosquitoes worshipwe feel your pain. Unfortunately, new data indicates that the number of mosquito species that feed on humans is increasing and the situation is likely to get worse.
Dr. SĂ©rgio Lisboa Machado, a microbiologist at the Universidade Federal do Rio de Janeiro in Brazil, is the co-author of a study published today in the journal Frontiers of ecology and evolution on a potential link between deforestation and mosquitoes’ growing preference for human blood.
Whose blood is it anyway?
In this study, Machado and his colleague, Dr. Jeronimo Alencar, examined the feeding habits of several species of mosquitoes in the Atlantic Forest, a humid deciduous forest that stretches along the eastern coast of South America.
According to Machado, the project began as an attempt to determine what local animals these mosquitoes were feeding on.
“When we started our research, our main goal was to find the preferred blood source that certain species of female mosquitoes use to reproduce,” says Machado. Popular science
The process of identifying the blood in the creatures’ stomachs took a long time. The first step was to identify which of the region’s approximately 40 mosquito species were biting. This involved careful examination of the creatures with a stereoscope.
“The identification itself is not complicated,” says Machado, “but there is a shortage of entomologists to carry it out.”
This fact, coupled with the need to bring the mosquitoes back to Rio de Janeiro for analysis, meant that by the time the samples were analyzed, the DNA and RNA they contained had begun to decompose. Despite these difficulties, the analysis gave Machado a pretty good idea of ​​which mammal species the mosquitoes in question preferred for dinner. In several cases, this blood was human.
“It was something we didn’t expect,” Machado says. “As we were in a forest reserve, we expected to find vertebrate DNA in the local fauna.”
Related Mosquito Stories
Changing tastes
So why so much human blood? Researchers hypothesize that the changing environment of the Atlantic Forest led these species to develop a taste for human blood.
“We think it’s a question of opportunity given the lack of a preferred food source,” says Machado. “It seems that if mosquitoes can’t find their preferred blood source, they look for whatever is available.”
As biodiversity declines and animal species disappear, more and more food sources for mosquitoes disappear. However, unlike most of the animals they feed on, mosquitoes are adaptable creatures. There is almost always a ready-made alternative, including humans.
While this may be good news for mosquitoes, it may be terrible news for humans. As an increasing number of mosquito species develop a taste for humans, the risk of species that were not particularly problematic in the past becoming new vectors of blood-borne diseases also increases.
Once mosquitoes acquire a new food source, they tend to develop a preference for that particular blood – and humans are a species whose availability is most certainly limited. not in decline. Today, the Atlantic Forest occupies barely a quarter of its former surface area, and it is not the only one. With each passing year, more and more wilderness areas are disappearing due to human incursions.
The answer appears to be to first stop and then reverse this process of deforestation and habitat destruction. But it is not entirely certain that the damage is so easily reversible. Humans certainly aren’t going anywhere, so who’s to say that mosquitoes won’t continue to happily feed on us regardless?
Machado expresses cautious optimism about how we can address the impact of deforestation on what mosquitoes eat.
“We believe this is a reversible process, but it will require restoration of the biome while we continue our study. We are still looking for more evidence that [these] mosquitoes have a preferred food source. For now, we observe that it is possible that they adapt to different sources and do not do so. [prefer] human blood. »
Jumping species
Nevertheless, humanity continues to play with fire as it moves deeper and deeper into previously unspoiled ecosystems. A landmark 2001 study found that new diseases are twice as likely to be zoonotic – transmissible between animals and humans – as existing diseases. The danger posed by such diseases has been illustrated by COVID-19, which jumped from bats to humans with catastrophic effect.
While the dire scenarios surrounding a new pathogen spread by mosquitoes are hypothetical, there are also very real dangers linked to deforestation. For example, the malaria parasite in the Amazon is widely spread by Anopheles darling mosquito. It was thought to have been eradicated in the 1960s, but it reappeared in the 1990s and is now common. Another study found that cleared forest areas had created a perfect breeding environment for the insect, encouraging its return.
Ultimately, Machado emphasizes that it is important to control the emergence of new disease vectors and thus mitigate additional risks.
“Recovery of ecosystems will certainly contribute to this and should minimize the climate changes we are experiencing,” he says. “We must learn that our actions today, no matter how small, will always have global repercussions in the future. »
PopSci Outdoor Gift Guide 2025
