It’s that again season there, the one where stay outside in the cooler hours of the day it is pleasant if it weren’t for the nuisance of mosquitoes. Which, we have also learned thanks to direct experience, do not sting by chance. In fact, today we learned something about their preferences. Matter of physics and chemistry: in fact, mosquitoes are sensitive both to heat and to certain smells, which they use to choose who to bite. So, for example, those people who have it on their own are preferred by mosquitoes skin high levels of carboxylic acids, as well as those with higher temperatures and higher levels of lactic acid (as occurs in sportsmen) and which emit more carbon dioxide. Today, thanks to a couple of studies released in succession in recent days, we also know something more, and hopefully we are closer to finding a way to avoid stings.
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It will probably be redundant to reiterate this, but the stings of mosquitoes they are not – especially outside our borders – just a nuisance. They are a major health problem: mosquitoes (several specie) I am vectors of various diseases, from malaria, to dengue, to yellow fever, to chikungunya. Escaping them or modifying them so as to prevent them from acting as vectors is a topic of great interest in the research field, parallel to that which aims to develop vaccines. Studies that try to understand what attracts mosquitoes fall above all in this area, and of course, they also aim to develop one day repellents that keep them away from us even in the absence of important health risks.
Soaps that attract and repel mosquitoes
In the last few weeks, we said, the results of two (small) studies have arrived that help us better understand the preferences of these insects. Il primo that’s what arriva by Virginia Tech researchers and confirms that yes the soaps used to wash can make a difference. In fact, when some volunteers (5) used muffs to capture the scent of their skin after having washed with different soaps or not, the mosquitoes (species Temples of the Egyptians, the yellow fever mosquito) showed preferences. Specifically three of the four soaps used were attractive, one, the coconut one (the others were fruity or floral) no. It’s just the beginning, what is called a proof-of-concept, the researchers warn. In short, too early to give indications on soaps, but what has been observed confirms that the mix of personal smells and that of soapsi alters the behavior of mosquitoes. For how long and how by virtue of the aroma of one’s own skin, it remains to be understood.
A field test in Zambia for mosquitoes
The other study instead comes from Zambia where a curious experiment was set up: “The Greatest Multiple Choice Test for Mosquitoes”he explains Diego Giraldo della Johns Hopkins Bloomberg School of Public Healthone of the first authors of the study, innovative in terms of dimensions – a cage, better a tent, of a thousand cubic meters – but also in terms of conditions: “We conducted the experiments in almost natural conditions, where the mosquitoes are exposed to natural variations in the weather. Furthermore, we used theodor of the whole body of the participants instead of only the smell of specific parts of the body”. To lead their field olfactory testin fact, the researchers have positioned around this large tent containing the mosquitoes (of the species Anopheles gambiae, among those responsible for malaria) 8 small one-person tents, where volunteers can stay for a few nights if necessary. Pipes then carried their smell directly into the central tent, where the mosquitoes were released at night. In the central tent, the olfactory test for the mosquitoes’ preferences was done by observing how aluminum discs heated to 35°C were positioned on the landing platform connected to the tubes to mimic the temperature of the skin Human, they explain the authors on Current Biologyconnected to infrared cameras.
Mosquitoes hunt for non-random prey
As hypothesized, air currents, heat, carbon dioxide, smells, and probably also the sight once in the vicinity of the host, influence the movement of the mosquitoes. In terms of individual preferences, it shows that some people are more attractive than others, and the reason must be sought in their smell, which can be reduced to a series of volatile compounds. “An important finding of our study is that carboxylic acids and acetoin (substances produced by the sebaceous glands and the microbiota, the authors recall, ed.) are associated with high attractiveness and eucalyptol is associated with low attractiveness to the malaria mosquito Anopheles gambiae – Giraldo resumes – Previous studies have observed that carboxylic acids are associated with a high attractiveness to the yellow fever mosquito Aedes aegypti.”.
Repellents or sting traps
Despite the innovative character of the study setting, even in this case thinking of exploiting what has been observed in order to make it already applicable is premature, the researcher admits: “This study was only conducted on a group of six people, and for now we can only say that eucalyptol is associated with low attractiveness”perhaps deriving from the aromas present in the diet or from a diet rich in vegetables. “We cannot yet confirm if theeucalyptus acts as a repellent, but we hope to run a much larger test to confirm this. We hope this screening will allow us to find more compounds in human odor that repel mosquitoes.”. Or on the contrary, understanding those who attract them, use them to create traps to divert the attention of mosquitoes, has explained Conor McMeniman della Johns Hopkins Bloomberg School of Public Health, head of the study. In the future, the team will continue the studies trying to understand if there are some factors, such as diet and the skin microbiota, which influence the odors emitted by a person, perhaps also trying to exploit this information as an alternative to repellents: “By studying these aspects we will have information on which diets or behaviors could alter the odors emitted by a person to reduce the attraction of mosquitoes”concludes Giraldo.