2023-06-13 16:00:00
Mosquitoes are among the deadliest animals in the world, as they are vectors of important infectious diseases, such as malaria, yellow fever or the West Nile virus. However, of the thousands of existing species, only a few like human blood, and even among members of the same species, different preferences have been observed. Why are we so irresistible to some while others are indifferent?
Scientists have been studying these insects for decades, in some cases with the intention of eradicating populations through gene editing, with the aim of ending disease vectors. Until now it was known that there is a relationship between the proliferation of mosquitoes and human concentrations, although there was little conclusive evidence capable of demonstrating this.
To fill this documentary gap, a team of researchers from Princeton University spent more than three months working side by side with a network of local collaborators in sub-Saharan Africa collecting eggs of one of the most harmful species: Temples of the Egyptians, responsible for Zika, dengue or yellow fever. His conclusions, published a few years ago in the magazine Current Biologythey put black on white what kind of mosquitoes bite humans, and where they come from.
There are two subspecies of Temples of the Egyptians: one of them prefers humans, while the other prefers animals. Most insect populations are a genetic mix of both, so finding a common denominator between them is especially helpful when determining which species is most harmful to humans.
To carry out the experiment, the researchers set up a series of traps to collect the eggs that these mosquitoes left in the water. They placed them in large cities and rural areas, with the intention of making a sample that was sufficiently diverse. They then incubated them and quantified their behavior, letting them choose between a human or an animal host, explains geneticist and Princeton University postdoctoral researcher Noah. H. Rose, coaturor of the study, to National Geographic Spain.
Photo: Istock
“In most places, mosquitoes preferred animals, but in a small number of locations they preferred humans. When we built a model using environmental variables to try to explain this variation, we found that the intensity of the dry season was the best environmental predictor, but that the density of human hosts in an area also explained some behavioral variations,” the researcher says.
The higher the population density, the more taste for humans
The conclusions were clear: mosquitoes that came from very dense areas—approximately more than 2,000 people per square kilometer—liked humans better. If, in addition, those regions had a dry climate, the probability grew substantially.
“Humans create a good habitat for mosquito larvae. We store water in tanks for later use and discard items such as tires and buckets that represent a perfect habitat for mosquitoes. Also, near those habitats, these insects have at their disposal large amounts of human blood that these insects use to develop their eggs,” explains Dr. Rose.
genetic differentiation
The experiment found that mosquitoes that liked humans were genetically different from those that liked other species, suggesting that this differentiation arose in one place and then spread across Africa.
“The results tell us that mosquitoes evolved to specialize in human hosts and habitats in response to increasing human domination of the territory, and it is likely that they will also evolve in response to future urbanization,” explains Rose.
the article of Current Biology he focused on evolutionary history, but his findings could have implications for public health. The results, combined with United Nations climate and population data, suggest that rapid urbanization in sub-Saharan Africa will bring with it a high concentration of ‘man-eating’ mosquitoes.
“Nature is responding to population growth” Noah. H. Rose, geneticist at Princeton University
“The rapid growth of large cities in Africa presents a major ecological shift, and nature is responding to this new threat,” Hoah reasons. H. Rose- However, our actions also make a difference. If people have access to clean water, good housing, and steps are taken to reduce mosquito habitat, we can prevent these insects from spreading so many diseases.”
Our ecological footprint has a bigger impact than it may seem. It will depend on our actions to keep the transmission of viruses spread by these not insignificant insects at bay.
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