Health Hazards: Bugs Versus Bug Spray
Barbara Lock, MDMay 29, 2009
Summer brings bugs, lots of bugs. A lot of blood-sucking bugs that can make us sick. In Central and South America, blood-sucking assassin bugs transmit trypanosomiasis, also called Chagas disease. In the tropics and subtropics, mosquitoes deliver malaria, yellow fever, and dengue (rhymes with ben-gay). While ticks may be best known as the vector of Lyme disease, they also transmit babesiosis, ehrlichiosis, and Rocky Mountain Spotted Fever, to name a few. And viral encephalitis, also courtesy of mosquitoes, occurs all over the world. These diseases are really no fun.
Much of the developing world is at risk for Dengue, which can cause fatal bleeding. Dengue is even present in the Caribbean, possibly on the island where you plan to take your family vacation. It is predicted to explode in Australia, where large reservoirs have been constructed to manage scarce water resources, perfect for breeding the vector mosquito Aedes aegypti, according to Beebe et al. Dengue is controlled in cities by spraying pesticides such as malathion from trucks. This is the same technique used by New York City to control West Nile Encephalitis.
Lyme disease, well known to cause a rash and total body symptoms that resemble the flu, can also cause heart disease and neurological p
roblems if left untreated. There is also some suggestion, propagated by Fritzsche, that Lyme disease may even be responsible for the excessive cases of Schizophrenia that occur in winter and spring, as the result of infection of pregnant women the previous summer. And Lyme disease is particularly common in June, July, and August. Summer campers are at risk for Lyme disease in endemic areas. The risk of any individual camper finding a tick on herself that happens to be infected with the Lyme-causing bacteria is about 4%, according to Sarwari et al, in a study based in a Lyme endemic county in Maryland.
Thank heaven for bug spray.
But wait, what’s in insect repellant, anyway? Most insect repellant is formulated with N,N-diethyl-m-toluamide, otherwise known as DEET. The appropriate use of DEET-containing products appears to be generally safe, even in children and pregnant women, according to a review by Koren et al. Cases of seizures and neurologic injury have been reported (Lipscomb et al, Briassoulis et al) in children, however, even with standard skin application. Even low-concentration DEET can be absorbed rapidly through the skin, sometimes faster than high-concentraton DEET. The family-marketed insect repellant OFF! Skintastic with Sunscreen becomes absorbed into the bloodstream within 5 minutes of application, according to a study by Ross et al, whereas 3M Ultrathon, with a DEETconcentration suitable for deep jungle adventures, is absorbed in the skin much more slowly. The insecticide malathion and other toxic chemicals also bypass the skin's natural barrier more easily when the skin is slightly damaged, according to Nielsen et al. Even a case of eczema will do the trick. Slower absorption is better; no absorption is best. As organophosphate pesticides go, malathion is not as toxic to humans as carbofuran, which was recently banned by the EPA for use on food crops.
So what is an outdoor lover to do? Just consider the risks and benefits every time you reach for that bug spray. If you simply must go canoeing in the swamp at twilight, then a spritz of eau de mosquito may be in order. If you are going to a breezy beach in the middle of the day and you've already got some broken skin, maybe you can leave the bug juice at home. But don’t stay inside, you need the fresh air and exercise.
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