Mosquito ‘castration’ is new hope in war against malaria

By Maore Ithula

The familiar buzz of a flying female mosquito may be irritating to humans, but for her male counterpart, it is an irresistible mating signal.

American scientists have discovered that during mating, the male and female mosquitoes flap their wings together in harmony.

The researchers established this unique character of the insects when they eavesdropped on a male Aedes aegypti mosquito pursuing a female in mating flight, and recorded the couple’s courtship "love song". Scientists believe by understanding the mating patterns of the insects, it will be easy to control their numbers and thus control the diseases they cause, such as malaria, yellow fever and dengue.

These discoveries may inspire new ideas for interfering with the mating process of both Aedes aegypti and Anopheles gambiae, which carries malaria. "This opens up a whole new world for mosquito control," says Laura Harrington, associate professor of medical entomology, at Cornell University, a co-author on the paper. "For decades we have lacked new tools for the control of mosquito vectors."

Mosquito behaviour

"Malaria cases are at an all-time high and emerging infections, such as dengue hemorrhagic fever, are increasing at an alarming rate. New strategies will only come with a clear understanding of mosquito behaviour — a topic that has been neglected by scientists."

Traditionally, mosquitoes that carry malaria and dengue are kept in check by spraying insecticides, with limited success. A drive is now on to develop more sophisticated control strategies — which may involve "breeding out" the mosquitoes.

Creating sterile males and releasing them into the wild can trick the females into mating with a partner who will bear them no offspring. If enough of these sterile insects were released over a long enough period, then in theory, the target population would decline. More than 50 million people suffer from dengue fever each year.

Another strategy is to release mosquitoes, which have been genetically engineered so that they cannot transmit dengue virus.

"The big obstacle," says Prof Harrington, "is that females can tell if a male has been altered. We see the female kicking out at the altered male, and after a while, he loses interest.