Genetics and exercising

Jul 30, 2007 18:06 GMT  ·  By

The mosquito is much more dangerous than just the cause of a nasty itching. At the tropics, malaria is the greatest killer and mosquito-transmitted West Nile virus and it's already present in the US. Mosquitoes have been around for at least 175 million years and they are here to stay, with all our efforts of fighting against this 'plague'. In the US alone, there are over 170 species.

But for example when you are out on a picnic you may be the target of all the mosquitoes around, while your buddies can remain completely 'untouched'. 'How come' you might ask? Is it true that mosquitoes are attracted by certain individuals? "One in 10 people are highly attractive to mosquitoes," said Dr. Jerry Butler, professor emeritus at the University of Florida.

There are about 400 different chemicals emitted by the human skin and which the researchers have just begun to investigate, and which are connected with our 'attractiveness' for the mosquitoes. It seems that 85% of our vulnerability to mosquitoes is in our genes. "People with high concentrations of steroids or cholesterol on their skin surface attract mosquitoes," Butler told WebMD. "That doesn't necessarily mean that mosquitoes prey on people with higher overall levels of cholesterol, These people simply may be more efficient at processing cholesterol, the byproducts of which remain on the skin's surface," added Butler.

"Mosquitoes also target people who produce excess amounts of certain acids, such as uric acid," added entomologist Dr. John Edman, spokesman for the Entomological Society of America. "These substances can trigger mosquitoes' sense of smell, luring them to land on unsuspecting victims. But the process of attraction begins long before the landing. Mosquitoes can smell their dinner from an impressive distance of up to 50 meters (166 ft). This doesn't bode well for people who emit large quantities of carbon dioxide." said Edman.

"Any type of carbon dioxide is attractive, even over a long distance. Larger people tend to give off more carbon dioxide, which is why mosquitoes typically prefer munching on adults to small children. Pregnant women are also at increased risk, as they produce a greater-than-normal amount of exhaled carbon dioxide. Movement and heat also attract mosquitoes." said Dr. Joe Conlon, technical advisor to the American Mosquito Control Association.

So, practicing sports in a mosquito infested area is a bad idea. As you run, the mosquitoes detect your movement and head towards you. Panting means that you dump more carbon dioxide that forms tracks luring the mosquitoes. The uric acid from your sweat has the same effect. In this case, there is no need for a special body chemistry. "Some of the worst mosquito populations exist along coastal areas," Conlon told WebMD. "They'll fly 40 miles (64 km) for a meal," said Conlon.

Mosquitoes will breed with any water source, but they thrive in the case of stagnant water. That's why you should prefer a babbling brook to a pond on you backyard. "Even in a desert area, mosquito biting tends to be intense around a water source," said Conlon.

Mountain trips will get you rid off mosquitoes? "Although they're generally not active below 55o F (12.7o C), mosquitoes have been sighted in the Himalayan Mountains," Conlon told WebMD.

Arctic climates is what defeats them? "You're safe for most of the year. But mosquitoes flock there for a brief, three-week period between July and August. The Arctic National Refuge is one big bog, making the mosquito population there second only to that in the Florida Everglades." explained Conlon.

The chemical of choice used in repellents, since 1957, is DEET. By now, it is the most effective.

A new research found that repellents with 23.8% DEET (most contain 10-30%) protect for about five hours. For infants over 2 months DEET is safe only in concentrations lower than 10%. Picaridin, used since 1998, is as effective as DEET is, but it's more pleasant as it has a light, clean feel and is odorless. Other recommendation is lemon eucalyptus oil, traded as Repel. Lemon eucalyptus is safe for children older than 3 years.

The IR3535, commonly known as Avon's Skin-So-Soft, is weaker than DEET. "[DEET] has been in use for over 40 years and has a remarkable safety record. Only few hospitalizations have been reported, mainly due to gross overuse," Conlon told WebMD.

DEET must be used sparingly, and near open skin, eyes, mouth, and nose, under clothing, or near food must be avoided. Repeated applications can rise the potential toxic effects of DEET.

Other alternatives are soybean oil-based repellent, which was found to protect from mosquito bites for about 1.5 hours, and other short-lived protection oils -- citronella, cedar, peppermint, lemongrass, and geranium. Still, eucalyptus oil can have longer-lasting protection.

Mosquito traps can also offer protection. They emit mosquitoes attracting factors, like carbon dioxide, heat, moisture, and others, trapping or destroying mosquitoes. When located in good breeding spots, "they have knocked [mosquito] populations down," Conlon told WebMD.