In India, the mosquito-borne disease still causes 13 million infections and 24,000 deaths a year, according to WHO estimates.
Joba Edward, 27, is a fisherman by day and a human mosquito-trap by night. He is among three pairs of men recruited as ‘human landing collectors’ at one of 12 sites along Lake Kariba in the southern province of Zambia, to help scientists study the density, types and human-biting behaviour of the female anopheles mosquito that spreads malaria.
Malaria is a parasitic disease that spreads between humans through the bite of infected female anopheles mosquitoes. Once the parasite enters the human bloodstream, it invades the liver and then the red blood cells. Symptoms include fever, headache, sweats, chills and vomiting; if severe and untreated, the infection can kill.
Edward has volunteered to be human bait for mosquitoes that are out from dusk to dawn in search of a meal. His job is to sit from 6 pm to 6 am in shorts and a T-shirt (so his legs and arms are uncovered) outside a stranger’s home in Makuti village, about 500 metres from lake Kariba, to catch live mosquitoes as they bite him, using a mouth aspirator.
Another ‘human landing collector’ sits inside the room, where the family sleeps, to catch indoor-biting mosquitoes.
The two collect and label mosquitoes on an hourly basis, taking 15-minute hourly breaks during a 12-hour shift, for a Zambia Ministry of Health study funded by PATH’s Malaria Control and Elimination Partnership in Africa (MACEPA).
They get 100 kwacha ($10) for each five-day spell, during which they will have caught 300 to 400 mosquitoes.
Data collected since the study started in 2014 shows an increase in the proportion of the outdoor-biting anopheles arabiensis and a fall in the malaria-spreading anopheles funestus since Zambia began indoor residual spraying (IRS) to accelerate malaria eradication.
The study also confirms that IRS lowered sporozoite rates of plasmodium falciparum, the most deadly of the four species of human malaria parasites, in the anopheles funestus, the species that spreads the most malaria.
The anopheles funestus loves a human meal and the study shows it is possible to lower its density using IRS. Study data from the past three years also showed a shift in biting behaviour, with mosquitoes no longer the most active between 10 pm and 2 am.
“The anopheles is now most active at dawn and dusk, which shows that it is adapting to survive the increased use of IRS and mosquito nets,” says Kochlani Saili, an entomological surveillance officer with PATH.
Globally, preventive measures such as insecticide-treated bed nets, IRS and mass drug administration (MDA) have halved malaria incidence worldwide since 2000, resulting in 6.8 million lives saved.
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