James L. Cummins

Mosquitoes and Repellants by James L. Cummins 

In the United States, we look at mosquitoes as a nuisance–with their irritating, high-pitched whine that has us slapping at our own faces. But, worldwide, mosquitoes are much more than a mere pest. In other places around the globe, mosquitoes transmit diseases to more than 700 million people annually. 

Mosquitoes transmit the arboviruses responsible for malaria, yellow fever, dengue, and several forms of encephalitis, resulting in as many as three million deaths annually. We tend to think of these diseases as “other world problems,” but just this past year there were reported cases of dengue fever and the West Nile Virus here in the United States. Mosquitoes are found all over the world except in Antarctica. Only the female bites and she requires a blood meal to produce eggs, which she typically seeks out every 3 to 4 days. In a normal meal, she generally consumes more than her own weight in blood. The female lays her eggs, up to several hundred at a time, on the surface of water. 

For development, an environment of standing water is required. The quality of the water is of no consequence as they are known to lay eggs in fresh water, salt or brackish, marshes, containers, old tires, bird baths, or wherever standing water can be found. Despite what some may believe, mosquitoes cannot transmit HIV because the virus neither survives nor replicates in mosquitoes. The blood from its last meal is not flushed into its next victim during subsequent feeds so there is no need to be concerned with contraction of HIV. 

Mosquitoes use visual, thermal, and olfactory (smell) to locate a host, with smell being the most significant factor. Carbon dioxide, released mainly from breath, but also from skin, serves as a long-range airborne attractant and can be detected by mosquitoes at a distance of nearly 120 feet. Within closer range, skin temperature and moisture serve as attractants. 

Floral fragrances from perfumes, soaps, lotions, and hair-care products are also thought to attract mosquitoes. N,N-diethyl-3-methyl-benzamide, commonly known as DEET remains the gold standard, as far as repellants go. It is a broad-spectrum repellant that is effective against not only mosquitoes but also biting flies, chiggers, fleas, and ticks. In the United States, DEET is available in 5 to 100% concentrations. As a rule, higher concentrations provide longer-lasting protection.

However, for casual use, a concentration of 35% provides adequate protection under most circumstances. The American Academy of Pediatrics recommends that repellants contain no more than a 10% concentration for children 2 months and older. Despite what many believe, DEET has a remarkable safety profile.               

There are several organic and homeopathic alternative repellants offered but DEET remains the gold standard for protection. Additionally, the combination of Permethrin-treated clothing and the skin application of a DEET-based repellant create quite a formidable barrier against pervasive mosquito bites.

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