2023-06-23 06:00:28
Mosquitoes are annoying creatures that can turn a pleasant summer evening into an itchy, stinging nightmare. But did you know that some people are more attractive to these insects than others? Two recent studies have revealed fascinating factors that explain why human blood acts like a mosquito magnet. In this article, we will explore these groundbreaking findings and discuss the potential impact on the prevention of mosquito-borne diseases.
Geographical expansion of mosquito-borne diseases
Before diving into why mosquitoes are attracted to certain people, it is important to understand the magnitude of the problem of diseases carried by these insects. In colder countries like Europe, mosquitoes are mainly seen as summer nuisances, unpleasant but without any real major impacts on health. However, globally, mosquitoes are the deadliest animals to humans, causing more than a million deaths each year through the transmission of pathogens such as malaria, dengue fever, chikungunya and Zika virus. .
Unfortunately, the protection against these diseases provided by colder climates is likely to change significantly over the next few decades. According to the Intergovernmental Panel on Climate Change, the increased risk of transmission of infectious diseases by vectors such as mosquitoes is one of the concrete consequences of climate change. Warming will allow the geographical expansion of several of these vectors, in particular mosquitoes of the genus Aedes, responsible for the transmission of several dangerous arboviruses such as dengue fever, chikungunya, yellow fever and the Zika virus. Mosquitoes of the genus Culex, vectors of the Nile virus, as well as certain ticks transmitting the bacterium responsible for Lyme disease, could also spread to new regions.
Experts also predict that climate change could favor the emergence of diseases transmitted by mosquito vectors of arboviruses, including in colder countries such as those in northern Europe. It is therefore likely that these mosquitoes, once exclusively present in warmer countries, could be present in 197 countries by 2080, which could lead to the appearance of serious infectious diseases.
Molecules in the skin that attract mosquitoes
Now that we understand the magnitude of the problem of mosquito-borne diseases, let’s look at the fundamental question: why are humans particularly popular prey for these insects? Two recent studies, published in the prestigious journal Cell, have provided important answers to this question.
In the first study, the researchers sought to identify molecules produced by the skin that are detected by the olfactory system of female mosquitoes and allow them to preferentially navigate to human blood. They compared the volatile substances secreted by people who are highly attractive to mosquitoes to those emanating from people who are less attractive. This approach found that the attraction of mosquitoes to humans was mainly determined by the levels of carboxylic acids present on the skin, in particular pentadecanoic, heptadecanoic and nonadecanoic acids.
These results pave the way for the development of next-generation mosquito repellents, capable of interfering with the detection of these substances and preventing the transmission of viruses carried by these mosquitoes. By specifically targeting these carboxylic acids, it may be possible to significantly reduce the attraction of mosquitoes to humans and therefore decrease the risk of disease transmission.
The influence of the skin microbiome on mosquito attraction
In the second study, the researchers observed that viruses carried by mosquitoes could also influence the attraction of these insects to humans. Using mice as a model, the researchers showed that the flavivirus vector mosquito showed a clear preference for animals already infected with a flavivirus such as dengue or Zika. Further analysis revealed that this attraction was due to the presence of a volatile molecule called acetophenone.
This mechanism also seems to be present in humans, since this substance is secreted in large quantities in patients with dengue fever. An interesting finding from this study is that the production of acetophenone is caused by an increase in certain bacteria present on the skin, made possible by the suppression of antibacterial defenses by the virus.
In other words, flaviviruses have developed a strategy to increase the attraction of mosquitoes towards the humans they infect, thus promoting their large-scale spread. However, the researchers also observed that the antibacterial defenses of subjects infected with flaviviruses can be reactivated by administering a derivative of vitamin A, thus reducing the attraction of mosquitoes and interrupting the transmission cycle of the virus.
These findings could open new perspectives for the development of prevention strategies against mosquito-borne diseases. By specifically targeting bacteria in the skin and enhancing antibacterial defenses, it may be possible to reduce the attraction of mosquitoes to humans and thus limit their potential for viral transmission.
Prevent the risk of mosquito bites
Understanding why mosquitoes are attracted to certain individuals is essential to developing effective strategies for preventing diseases transmitted by these insects. Recent findings on molecules in the skin and the influence of the skin microbiome open up exciting new avenues for the development of next-generation mosquito repellents and solutions to reduce the potential for virus transmission.
As climate change continues to favor the geographic expansion of disease-carrying mosquitoes, it is crucial to continue research in this area to better understand the mechanisms of attraction of mosquitoes and to develop effective means of prevention. By combining our knowledge of skin molecules, the skin microbiome and the interactions between viruses and bacteria, we could one day achieve a significant reduction in the impact of mosquito-borne diseases on human health.
Stay informed and protect yourself against mosquitoes by taking effective prevention measures, such as using repellents, wearing long clothing, and removing standing water that is conducive to mosquito breeding. Together, we can control these insect pests and prevent the spread of the diseases they carry.
Sources
According to Kraemer MUG et al. (2019). Past and future spread of the arbovirus vectors Aedes aegypti and Aedes albopictus. Nat. Microbiol. 4: 854-8
De Obaldia ME et al. (2022). Differential mosquito attraction to humans is associated with skin-derived carboxylic acid levels. Cell 185: 4099-4116.e13.
Zhang H et al. (2022). A volatile from the skin microbiota of flavivirus-infected hosts promotes mosquito attractiveness. Cell 185: 2510-2522.e16.
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