Salt to avoid the bite of kissing bugs and mosquitoes?

The insect popularly known as kissing bug and sometimes also called kissing bug for its habit of biting near the person’s mouth, is dangerous, among other things, because it can transmit Chagas disease, caused by the Trypanosoma cruzi parasite.

A group of researchers from the National Council for Scientific and Technical Research (CONICET) of Argentina, which is dedicated to studying the taste system in insects that feed on blood, has managed to describe the behavior of the vinchuca Rhodnius prolixus. Thus, these scientists have discovered that it avoids feeding if the substrate where it tries to bite has high levels of salt.

The specialists used artificial membranes that imitated the skin of the host to be bitten by this kissing bug and impregnated them with different amounts of salt. “In low concentrations, this can be good, but in high concentrations it is aversive and that is what we described for the first time in a hematophagous insect, which, when confronted with a substrate with a lot of salt, refused to bite and feed,” he explained to the Agency. CTyS-UNLaM Romina Barrozo, study leader and CONICET researcher.

In addition to discovering this reaction, they were also able to identify and characterize the neural pathway to the kissing bug brain to find where this information is processed. “We saw that there were little hairs on the antennae, which are sensory structures called gustatory sensilias and that, inside, they contain neurons that are sensitive to the detection of salts,” she said.

“When we turned off or blocked the gene receptors in these neurons, kissing bugs began to bite and feed on salty substrate. This tells us that these receptors are responsible for detecting high levels of salt,” said Barrozo, who is also head of the Insect Vector Neuroethology Group of the Institute of Biodiversity, Experimental and Applied Biology (IBBEA), attached to CONICET and the University of Buenos Aires (UBA).

In the experiments of the study, it has been verified that the vinchuca Rhodnius prolixus avoids feeding if the substrate where it tries to peck has high levels of salt. (Photo: CONICET / CTyS-UNLaM Agency)

With these results, specialists are already working in the laboratory to extend the study to other hematophagous insects such as mosquitoes, including Aedes Aegypti, vector of Dengue, Zica and Chikungunya. Until now, only preliminary tests have been carried out, but, according to the researcher, everything indicates that they could present the same rejection.

“The vinchucas, the mosquito and the fruit fly have an orthologous receptor. This means that they have a common ancestor and possibly the same function. There may be some small variation in mechanistic detail, but we believe that all blood-sucking insects may exhibit this aversion behavior,” he explained.

Towards a new generation of repellents

Identifying this behavior is not only important to learn more about this type of insect, but also for its possible contribution in terms of health, since both mosquitoes and vinchucas are vectors of diseases that are endemic in countries like Argentina. The development of new repellents could contribute to its prevention.

In previous studies, the effect of substances of natural origin with repellent action, such as caffeine and quinine, was demonstrated. “These compounds, which for humans are bitter and we consume in various beverages, cause a rejection action in insects because they have an inherent toxicity involved. This means that there are many plants that produce these compounds to avoid being eaten by vertebrate predators or insects, ”he detailed.

In that sense, this information is key to the development of natural repellents that do not impact the environment or people’s health. “Taking advantage of this knowledge, we are looking at the molecules that trigger this aversion to start looking for the advantage in this system and producing new, friendlier products,” he said.

Lastly, the head of the IBBEA Insect Vectors Neuroethology Group maintained that these repellents would function as a second instance of defense. “The repellent commonly used as the OFF is detected from a distance by the olfactory system of the mosquitoes. This new generation of repellents in which we are interested are products that, in addition to being natural, are the target of another sensory system that is taste, so we would obtain double protection”, she concluded. (Source: Marianela Ríos (CTyS-UNLaM Agency))