(Beyond Pesticides, May 13, 2010) Recent tests find that mosquitoes that are insensitive to DEET, the pesticide commonly used to repel the pesky flying insect, can pass this characteristic as a genetic trait onto their offspring. The findings are published in the May 3 edition of the journal Proceedings of the National Academy of Sciences.
In order to hunt for blood, female mosquitoes use their antenna to locate humans; however, according to researchers, DEET temporarily destroys an insect’s sense of smell by hindering the function of certain odor receptors. The researchers observed which insects bit DEET-treated human arms and discovered that a gene alteration prohibited a sensory cell on the bugs’ antennae from detecting the chemical.
“There is something in the antenna they use to smell that reacted differently,” Dr. Nina Stanczyk of Rothhamstead Research, an agricultural research center in the U.K., told the Toronto Star.
Scientists studied one species of DEET-insensitive mosquitoes, the Aedes aegypti, a species that carry the diseases yellow fever and dengue fever. When mutated females were bred with males of unknown sensitivity in tests, the quantity of mosquitoes that were insensitive to DEET rose from 13 to 50 percent in one generation.
Though scientists are warning that this research is limited to the laboratory and admit that they are not concerned that the resistant bugs will spread tremendously, insecticide resistance in mosquitoes is nothing new. A 2003 study found that mosquitoes carrying West Nile virus and malaria developed resistance to organophosphate and carbamate insecticides as a result of a single genetic mutation. Such resistance renders the broadcast spraying of mosquito adulticides and overuse of repellents an inefficient form of control that puts public health and the environment at risk to the chemical’s adverse effects.
For years scientists have raised concerns about the use of DEET and seizures among children, even though the U.S. Environmental Protection Agency (EPA) says that there is not enough information to implicate DEET with these incidents. DEET is quickly absorbed through the skin and has caused adverse effects including severe skin reactions such as large blisters and burning sensations. Use of DEET by pregnant woman has been linked to birth defects, and laboratory studies have found that DEET can cause neurological damage, including brain damage in children.
DEET’s synergistic effect with other insecticides is also a major health concern. DEET, when used in combination with permethrin -a synthetic pyrethroid insecticide, likely facilitates enhanced dermal absorption of permethrin and induces symptoms such as headache, loss of memory, fatigue, muscle and joint pain, and ataxia, which causes an inability to coordinate muscular movements.
There are many least-toxic options for repelling insects that include the use of citronella and other essential oils, like oil of lemon eucalyptus, which has been recommended as an efficacious alternative by the Centers for Disease Control and Prevention (CDC).
Source: National Geographic News