‘Dieting’ mosquitoes for disease control
Female mosquitoes can be tricked into thinking they are full and so they don’t bite a human for a meal...
Mosquitoes are one of the deadliest animals in the world: each year they are responsible for the death of millions of people by spreading diseases like malaria, yellow fever, dengue and, more recently, Zika virus. When a mosquito takes a blood meal from an infected person, it becomes a vector of the disease and can infect anyone else it bites afterwards.
Now researchers at the Rockefeller University in New York, writing in the journal Cell, have demonstrated a new way to curb the biting behaviour of mosquitoes. According to the study's lead author, Laura Duvall, “actually, only female mosquitoes bite and they use the protein in our blood in order to develop eggs... in fact, when she takes this meal she will double her bodyweight.” But unlike humans, who can experience hunger within a few hours of eating, once a female mosquito has a blood meal, she loses interest in biting people for several days.
Duvall and her colleagues wondered whether the signalling pathways in the brain that control food-seeking behaviour and appetite, including the full feeling that accompanies a large meal, may also be present in the mosquito.
The team dosed Aedes aegypti mosquitoes with a human appetite-suppressing drug. “We thought that the drug might still change the mosquitoes behaviour, and in fact they did! We showed that we can block the mosquitoes’ attraction to humans.”
The agents targets a receptor system in the mosquito called NPYLR7. “In humans, these receptors are involved in appetite, and there have been a lot of other people who have developed drugs to target the human versions,” explains Duvall.
Currently there are different methods to combat mosquitoes, there are some that physically block contact with humans such as mesh and bed-nets, while some lure mosquitoes to them using human scents and then deliver a deadly poison. Duval suggests that “we could imagine putting some of the drugs that we’ve found in a trap like this, where a mosquito would drink it and it would block her attraction to humans.”
The drug is not a permanent fix though. “It does in fact wear off; right now we can block mosquito attraction to humans for 2-3 days, but it will come back afterwards. That’s something that in the future, using what’s called medicinal chemistry, we can find improved drugs that would last for even longer.”
The researchers don’t yet know if the female mosquitoes are less sensitive to the presence of a human when given the diet drug, or whether she just loses interest in seeking a blood meal. But, with further research on the receptor mechanism, Duvall thinks the drug may be active in blocking other species of deadly mosquito and perhaps even ticks, who are known to spread Lyme disease.