Feeding Time in the Lab

Cameroonian entomologist Hortance Manda is based at ICIPE's Mbita facility, where she conducts research in a "semi-field environment," a series of greenhouses that replicate conditions among the farmers and fishermen of this indigent lakeside community. In rooms full of plastic breeding bins, Manda and her assistants cultivate between 4,000 and 10,000 mosquitoes a day for experiments that allow her to burrow deep into the biological mechanisms of Anopheles gambiae.

All mosquitoes eat plant sugars, and all females consume blood. But each of the 3,800 species is a bundle of feeding and gestational idiosyncrasies, differing in the plants they like to extract their nectar from, how much blood they require, and the animals they draw it from (only a fraction feed on humans). Manda has shown that Anopheles gambiae tends to be choosy about its sugar sources, generally favoring plants such as African senna and castor bean that are maximally nourishing. But she's also observed that this mosquito is unaccountably drawn to wild quinine, although the plant offers scant basic nutrition. Her hunch is that the malaria parasite Plasmodium falciparum may be playing a role here. "There is reason to believe that mosquitoes suffer from Plasmodium infection," Manda says. Strange to make common cause with the mosquito, but humans have long resorted to quinine under similar circumstances. "There may be something in the quinine that benefits the mosquito too," she believes.

In a hermetically sealed greenhouse containing a small thatched hut and a range of plants that would typically surround it, mosquito colonies are released by Manda and her associates, to be observed like unwitting stars of their own Truman Show. A lab assistant is recruited to spend the night on the house's tidily made bed, yielding his unprotected flesh to scientific inquiry into the feeding proclivities of Anopheles gambiae (lab-bred and not malarial). By clarifying the precise roles that various plants play in sustaining both male and female fecundity, Manda sees her research factoring into an overall integrated vector management strategy. With the widespread use of insecticide-treated bed nets in malaria-endemic regions, scientists speculate that mosquitoes may begin to favor plant feeding as less risky and less energy-consuming than blood feeding. According to Manda, removing relevant plants from areas of human settlement could further undermine the symbiosis between the vector and its besieged protein source.