The disconcerting list of illnesses spread by the flying disease-delivery vehicles known as mosquitoes is ever expanding. Along with vector-borne diseases, mosquitoes offer no shortage of itchy welts, with their maddening hum keeping the soundest of sleepers swatting at their faces all night.
Have you ever wondered if you are a frequent target of mosquitoes than anyone else? Well, it’s not just your imagination. Various studies reveal that mosquitoes do exhibit biting preferences for a variety of reasons and actually bite certain people more than others. According to lab research, about 20 percent of the population gets bitten more than others.
Though researchers have barely scratched the surface behind the reason why mosquitoes bite some people so much, they have laid out a few factors which could provide insight and help in taking effective preventive measures.
Adult mosquitoes survive on nectar for nourishment, but females rely on the protein in our blood for the production of eggs. So it brings little surprise that some blood types may be more desirable than others depending on the typical characteristics.
According to a study by the Journal of Medical Entomology, mosquitoes land on people that have Type O blood nearly twice as much as they land on people with Type A blood. Individuals with Type B blood fall somewhere in the middle of the spectrum. Also, about 85 percent of people secrete a chemical signal through their skin indicating their blood type which eventually helps the mosquitoes in choosing their preferred food source.
Carbon dioxide and Metabolism
Those with higher metabolic rates produce more carbon dioxide. Using an organ known as the maxillary palp, female mosquitoes can smell carbon dioxide emitted in human breath up to 115 -160 feet away; so the more one exhales, the more attractive they become. Those who exhale more of this gas- often larger people, seem to attract mosquitoes more than others. Since human beings exhale carbon dioxide through the nose and mouth, mosquitoes are attracted to the heads, which explains the whole misery of mosquitoes buzzing about the ears all night. But strangely though some mosquito species are leg and ankle biters; they cue into the stinky smell of bacteria on your feet.
Body temperature and Chemicals
Mosquitoes seem to have a nose for other scents, such as lactic acid, uric acid, ammonia and other compounds emitted in sweat. "Mosquitoes target people who produce excess amounts of certain acids, such as uric acid", explains entomologist John Edman, PhD, spokesman for the Entomological Society of America. Lactic acid- given off while exercising, acetone- a chemical released in a person's breath, and estradiol- a breakdown product of estrogen can all be released at varying concentrations and lure in mosquitoes.
Mosquitoes also prefer warm bodies. Exercise increases the buildup of lactic acid and heat, making a warm, sweaty body almost irresistible to mosquitoes. Movement and heat increases mosquito bites up to 50%."People with high concentrations of steroids or cholesterol on their skin surface attract mosquitoes," reports Jerry Butler, PhD, professor emeritus at the University of Florida. But that doesn't necessarily mean that mosquitoes prey on people with higher overall levels of cholesterol.
Bacteria on Skin
Research suggests that certain types and quantities of bacteria on human skin can attract mosquitoes. A recent study found that large amounts of certain types of bacteria make skin more appealing. This may explain why mosquitoes are drawn to our ankles and feet, which are areas that often harbour highly active bacteria colonies, and can be smelly.
The colour of clothes
Mosquitoes are highly visual, especially later in the afternoon, and their first mode of search for food sources is through vision, explains Jonathan Day, a professor of medical entomology at the University of Florida. Wearing certain colours including navy blue, black and red, can make you easier to spot. According to studies, dark colors have been shown to attract more mosquitoes than lighter colours.
Researches show that women in the late stages of pregnancy, mostly in 28-plus weeks are more likely to be bitten by mosquitoes than non-pregnant women. One possible explanation is that pregnant women exhale about 21 percent more carbon dioxide, hence will also be a bit more attractive to mosquitoes, as mosquitoes are attracted to carbon dioxide. Plus, pregnant women have a warmer average body temperature, which is a cue for biting and landing.
Scientists do know that genetics account for a whopping 85% of our susceptibility to mosquito bites. Research suggests that an underlying genetic mechanism may influence whether an individual gets bitten by mosquitoes or not.
In the words of Joseph Conlon, technical advisor to the American Mosquito Control Association, the latest thinking is that it might not be about what makes people more attractive to mosquitoes, but what makes them not a repellant. It could be that individuals who get less bites produce chemicals on their skin that make them more repellant and cover up smells that mosquitoes find attractive. It is relevant to note that scientists at the London School of Hygiene & Tropical Medicine have found that some people produce a chemical which works as natural mosquito repellent that appears to be genetic.
(Author is the Director -TGL Foundation, Chairperson CSA, Editor -The Intl Journal, Sr Dir FWO)