Outsmarting Olfaction: The Next Generation of Mosquito Repellents

Abstract

The world’s most dangerous animal weighs about two milligrams and pursues its human prey at speeds of barely a mile per hour. Surprised? Don’t be. The dubious honor belongs to the lowly mosquito—a fragile creature whose bite infects millions with lethal diseases, such as malaria, dengue, and West Nile encephalitis. For centuries, humans have slathered on insect repellents to deter the buzzing menace—the first recorded repellents were documented by Herodotus around 400 B.C. But these products have always been far from optimal. Even DEET (N,N′-diethyl-n-toluamide), the world’s most popular and efficacious repellent, has numerous shortcomings: it can require frequent applications, it must be applied to all exposed body parts, and it won’t protect against some dangerous mosquito species, including Anopheles albimanus, the chief malaria vector in Central America. Today, the need for more effective repellents is increasingly urgent, experts say. According to the World Health Organization, global climate change is expanding mosquitoes’ range, heightening the risk of disease for millions of additional people. The Centers for Disease Control and Prevention notes that dengue and West Nile virus are both moving from developing countries towards the United States, where concerns over mosquito exposure are rising. Malaria—which by various estimates kills between 1 million and 3 million people worldwide each year—is also a growing problem in many regions. This is in part because Plasmodium, the mosquito-borne parasite that causes malaria, is fast becoming resistant to existing treatments, such as chloroquine. Many experts believe that better repellents could help to control mosquito-borne diseases. These next-generation repellents must be effective against anopheline mosquitoes that carry malaria. They should also be cheap and nontoxic, and should last long enough to protect humans as they sleep, when they are most vulnerable. Where will these repellents come from? The answers, scientists increasingly say, will be found in genomic research. According to this view, knowledge of the genes and proteins that mosquitoes rely on to sense their environment could lead to new repellents that directly interfere with the insects’ ability to detect human beings.