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Why do mosquitoes bite you? Well, there is science behind it

Medical professionals in this article explain why mosquitoes bite certain people more than others and what can be done to keep the mosquito-borne diseases at bay.

Shreya Khanal, Dr Nisha Regmi, Dr Ranjan Regmi and Dr Kamal Raj Baral

Are you among those who often get mosquito bites? Or have any of your friends, family members or relatives been infected by mosquitoes? Have you ever wondered why it is so? Have you ever considered the pattern or preference of mosquitoes to feed on a specific individual? There could be a few reasons why a person gets mosquito bites frequently. And it’s not a new phenomenon.

Mosquito-borne infections are common throughout the world. Mosquitoes that bite humans are female because their eggs require more proteins to reproduce. They feed on our blood and cause red lumps on our skin. This is due to an enzyme injected by mosquitoes. When a mosquito arrives on human skin, it punctures it with two tubes: One sucking blood and the other for injecting an enzyme to prevent blood clotting.

Some persons are more likely to get infected more than once by any mosquito-borne illness. According to Healthline and some other research, this is due to reasons other than chance. Mosquitoes locate their hosts by sensing infrared radiation released by human warm blood, studying our signals, and employing chemicals. Following are some of the elements that may be connected with your attraction to mosquitoes, or mosquitoes’ attraction to you, near you.

Five factors

First, the blood group. According to numerous research conducted in 1974, 2004, and 2019 to examine mosquito blood type preference, blood group “O” seems to attract more mosquitos than the other three blood groups. Individuals with various blood types have different sets of proteins on the surface of their red blood cells known as antigens. These proteins can be found in some people’s saliva or tears. Individuals with blood type A would be type A secretors, those with blood type B would be type B secretors, and those with blood type O would be type O secretors. Since studies indicate that mosquitoes landed on people with O blood group under the same conditions–same place and equal amount of skin exposed–it is possible that mosquitoes can sense these antigens in a secretor, which is present in their tears and saliva. Although there hasn’t been enough research to back up this theory, available evidence suggests that mosquito blood type preference is connected with blood type O.

Second, according to a 2016 study, carbon dioxide plays an important role in mosquitoes’ aggressive quest for hosts. The huge amount of CO2 emitted puts an individual in danger of mosquito bites because mosquitoes can smell and navigate it from 164 feet away. Similarly, a 2004 study found a link between pregnancy and mosquito attraction because pregnant women have high body temperatures and tend to breathe heavily. Pregnant women, persons of greater stature, fitness freaks, and those who exercise are more likely to be bitten by mosquitos because they exhale more CO2 than others. One study from West Africa found that the women, on average, received over seven times more bites per night than the children. As a result, adults are at a larger risk of mosquito-borne illness than children.

Third,  certain substances found in our skin and sweat have been identified to attract mosquitos’ attention to prey. Among the various components, lactic acid and ammonia are essential. Lactic acid is 10-100 times more plentiful in human leftovers than in other animals, and female mosquitoes are more sensitive to it when exposed to CO2. Similarly, ammonia has been discovered to be abundant in human perspiration. Similarly, a 2015 study discovered that mosquitoes were significantly attracted to odors from identical twins’ hands. Besides, a study conducted in 2011 indicated that skin bacteria play a crucial role in body odor, with persons with a large diversity of microbes on their skin being less attractive to mosquitoes.

Fourth, studies have discovered that genetics account for 85 percent of an individual’s sensitivity to mosquito bites. Blood group, body odor, and the hands of identical twins are all directly or indirectly related to inherited genes. Individuals with higher levels of steroids or cholesterol can also contribute to mosquito attraction. This does not imply that mosquitoes like cholesterol, but that humans with high cholesterol are more efficient at processing it, a result of which lingers on the skin’s surface. 

Finally, a  2002 study discovered that mosquitoes were more attracted to those who drank beer than to people who did not. 

Keeping mosquito-borne illnesses at bay 

Despite the numerous efforts globally, the number of mosquito and mosquito-borne illnesses is rapidly increasing. The developing and underdeveloped countries are most affected by the adverse effects of the mosquito-borne diseases. Over the last few decades, many methods have been developed for their control and the main goal of these strategies is to reduce the number of mosquito populations to overcome the epidemic situations. Despite ongoing efforts with current interventions in vector control programs, we are still unable to effectively control disease transmission and outbreaks.

By 2050, approximately half of the world’s population is expected to be at risk of arboviral transmission. The rapid increases in the geographic distribution of these mosquitoes and the diseases transmitted by them have contributed significantly to global mortality and morbidity. Vector-based interventions are the most common methods to reduce the burden of most mosquito-borne diseases. A wide range of tools exist for this which are mentioned below.  This includes chemical methods and non-chemical methods. 

The chemical methods involve the use of insecticides, Insecticide-treated materials (ITMs) as Insecticide Treated Nets (ITNs), for spraying on indoor surfaces as Indoor Residual Spray (IRS), and among the non-chemical methods, it involves the use of biological and genetic innovations. The basic purpose of vector control is to restrict disease transmission potential by minimizing or eliminating human contact with the vector. To control malaria, in malaria   elimination programs, Long-Lasting Insecticide Nets (LLINs) and IRS are being used to control the transmission in high malaria endemic areas but due to emerging insecticide resistance, the mosquito vectors do not remain susceptible to these insecticides.

Chemical control involves the application of products designed to kill mosquitoes, either in the larval stage through physical damage or hormonal disruption, or in the adult stage through nervous system disruption. The methods include, among other things, indoor residual spraying (IRS),  using  insecticide treated nets (ITNs) and using ultra-low volume sprays (ULV). Non-chemical methods include using natural predators of mosquito larvae like Mosquito fish and releasing sterile male mosquitoes into the wild population, among others.

To sum up, mosquitoes, particularly the females who seek our blood for egg production, are drawn to certain individuals for a myriad of reasons. Factors like blood type, carbon dioxide emissions, body odor, cholesterol levels, as well as alcohol consumption can influence a mosquito’s preference for its next meal.

While mosquitoes may seem inevitable, preventive measures are at hand. There are strategies to minimize contact with these buzzing bloodsuckers, from chemical methods like insecticides and repellents to non-chemical approaches such as biological control and genetic innovations. So next time you’re scratching those itchy bites, remember, there’s science behind the swarm.

Co-author : Dr Nisha Regmi, Dr Kamal Raj Baral and Dr Ranjan Regmi

Shreya Khanal is a postgraduate student of MPH-IR at Gadjah Mada University, Indonesia (Email: [email protected]). Dr Nisha Regmi, Dr Kamal Raj Baral and Dr Ranjan Regmi, all MBBS, are with College of Medical Sciences, Teaching Hospital, Bharatpur, Chitwan (Email: [email protected], [email protected] and [email protected] respectively.)