Mosquitoes' last supper

of the world and are particularly abundant in towns and cities where the climate is warm and water is plentiful. A. aegypti mosquitoes buzz about at dawn and dusk in search of their next blood meal, preferably from people’s ankles.

A. aegypti mosquitoes are the main vector for dengue fever, now the most common viral disease transmitted by mosquitoes. Dengue fever has made a comeback especially in subtropical and tropical regions due to the geographical spread of the mosquitoes and the virus. Four strains, or serotypes, of disease-causing dengue viruses are known.

When infected for the first time, most people suffer through a bout of high and painful fever, but usually the illness is not life threatening and renders them immune to that particular strain of dengue virus. A subsequent infection, however, with any of the other dengue virus strains often triggers an all-out immune response that leads to a much more severe form, called dengue hemorrhagic fever, which can be fatal.

Miesfeld said most mosquito-borne pathogens are not passed down from the female mosquito to her offspring, but instead picked up by the mosquitoes when they bite an infected human.

In the case of A. aegypti mosquitoes, the pathogen is often dengue or yellow fever viruses, whereas the Anopheles gambiae mosquito, which is found in many parts of Africa, transmits the more deadly malaria parasite. Miesfeld further explained that malaria and dengue pathogens take about ten to twelve days to complete their life cycle within the mosquito before they can be transmitted to humans through blood feeding.

“The most dangerous mosquitoes are the older ones,” Miesfeld said.

His team used a technique called RNAi specifically to target genes that are required for the digestion process. The researchers homed in on a protein complex called COPI, which stands for coatomer protein 1.

COPI consists of several subunits that together make up the envelope of the vesicles on which the cell relies for internal transport and for secretion of enzymes into the gut.

When a female mosquito takes a blood meal, the cells lining its gut secrete enzymes to break down the blood proteins. The secretion process involves packaging the enzymes in small droplets called vesicles that the cells then release into the gut.

“We thought, ‘Why don’t we knock out the whole process that allows the proteases to be secreted?’ That’s where we got this amazing result,” Miesfeld said. “Not only did we eliminate her ability to secrete anything,