Mosquitoes are more than a nuisance. Researchers say that children, especially when down with malaria, are more attractive to mosquito bites, and thus the need to protect them.
The rains are here, and so are mosquitoes. Unfortunately, mosquitoes reveal fatal attraction for children, explaining why malaria still kills a child every two minutes in the world.
There are hundreds of mosquito species and they all have slightly different preferences when it comes to what or who they bite. But researchers believe that children infected with malaria are more attractive to mosquitoes.
In a new study, researchers found that children infected with the malaria parasite Plasmodium produce distinctive skin smells making them more attractive to malaria mosquitoes than uninfected children.
This study, which opened up the possibility of developing a system to lure mosquitoes away from human populations, or in diagnosing malaria, was published in Proceedings of the National Academy of Sciences.
Breath diagnostics are used for such diseases as tuberculosis because certain diseases or malignancies cause a change in odorants in the breath of the patients, and those changes can be used to detect disease.
In the study, researchers first confirmed the increased attractiveness of children with malaria by measuring the attractiveness of their skin odour, on socks of 45 Kenyan schoolchildren, some infected by malaria.
Its next stage was to understand the mechanism behind this increased attractiveness among children aged four to 12 years that participated in the study.
They found the samples that interest mosquito the most, and were, therefore, most likely to draw a bite, were from the children with malaria. The malaria group was particularly high in a group of chemical compounds called aldehydes in their sweat.
According to them, if infected people smell better to mosquitoes, that could increase the likelihood that the insect sucks the parasite along with its blood meal, then spreads the infection by biting someone else.
By preying on mosquitoes’ attraction to the parasite’s aldehyde signal, the team believes they could develop a new wave of traps to lure mosquitoes away from human populations or detect infections.
Dr Chiaka Anumudu, a malaria immunologist at the Department of Zoology, University of Ibadan, said studies before now have established that mosquitoes are attracted to humans for different reasons, including smell.
According to her, “studies that have shown that people who have feet that smelled like cheese, mosquitoes are attracted to those kinds of smell.”
Dr Anumudu added that the odour of the exhaled carbon dioxide and the body odour, which is the sweat mixed with bacteria, even at distances as much as 50 yards could aid the mosquitoes in locating who it wants to bite.
Nonetheless, she added that since adults produce more carbon dioxide than children, children would certainly experience fewer mosquitoes’ bites.
“That is why people apply insecticide repellent on their skin to mask body scent, so making it difficult for the mosquitoes to be attracted to them aside that the killer action of repellents on mosquitoes,” she declared.
Dr Sam Awolola, Deputy Director & Head, Public Health Department, Nigerian Institute of Medical Research (NIMR), said irrespective of the presence of Plasmodium, the germ that causes malaria, mosquitoes are well known to be attractive to human beings due to exhaled carbon dioxide and other gases such as lactic acid and ammonia from the body.
Awolola, an entomologist, however, said that amounts of emitted gases like carbon dioxide can vary from one person to the other based on the physiology of their body.
“Somebody that snores when sleeping, of course, tends to release more carbon dioxide than another person that does not snore
“So the possibility that such a snorer will attract more mosquitoes to himself is higher. Mosquitoes are always drawn to sources of carbon dioxide,” he declared.
Moreover, Dr Awolola said things like dirty, smelly socks as well as a room heavily lit with candles had been found to attract mosquitoes to it.
“If you put on socks after a while sweat is deposited on the socks. So you have a lot of ammonia, lactic acid and so on soaked into the socks. If such smelly socks are hung somewhere, mosquitoes also get attracted to them.
“It is like houseflies. Where there are faeces, houseflies will be drawn to it. It is the faeces that draw the houseflies and not the person that passes out the faeces.
“Also, a room with lots of candles lit and giving out carbon dioxide will attract more mosquitoes to it. It is scientifically proven that you can attract mosquitoes without humans if you put carbon dioxide gas in a place.
“This is the basis of the light trap. We also trap mosquitoes by using the light trap, putting carbon dioxide into the light trap and it attracts them,” he declared.
But, the possibility that children with Plasmodium parasites, which cause malaria, are more attractive to mosquitoes, he said still needs to be further assessed.
According to him: “Mosquitoes come to humans because they want to have a blood meal. What attracts them to have a blood meal is the human odour. It has nothing to do with the Plasmodium parasites inside the human body.
“There is no linkage between the malaria parasite inside the blood and the mosquitoes that fly around. This is a basic science.”
The female mosquito is the one that bites; males feed on flower nectar. She requires blood to produce eggs. Her mouthparts are constructed so that they pierce the skin, literally sucking the blood out.
There is growing interest in the potential role odour plays in spreading the disease and how it could be used to help diagnose and reduce the spread of the illness.
Previously, some scientists suggested that certain characteristics attract mosquitoes, thereby leading some people to have more bites than others. Aside the amount of carbon dioxide in the breath, others include pregnancy, body temperature, alcohol and odorant markers based on blood type.
One study found persons with Type O blood suffered more mosquito landings because of the odourant markers they emit than any other blood type.
Pregnancy is a big winner for mosquito attraction, probably because mothers-to-be exhale 21 per cent more carbon dioxide and are on average 1.26 degrees Fahrenheit warmer around the belly than their non-pregnant counterparts, due to the temperature of the amniotic fluid.
Also, having just 12 ounces of beer increases mosquito appeal, possibly because of the increase in body temperature it causes or because skin markers change when metabolising cocktails.