‘Human bait’ volunteers are helping beat malaria in Zambia

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.

Nothing can prevent the itch from the bite, but that doesn’t bother Edward. ‘I’m not itchy because I’m very fast. I catch them before they can bite me,’ he says. Edward last had malaria three years ago. ‘I’ve not had malaria since I started this volunteer work,’ he says.

ENDING MALARIA

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.

The MACEPA study is adding to the knowledge arsenal in the global fight against malaria, which has been eliminated in seven countries since 2000. Zambia is leading the charge in Africa by accelerating its efforts to be malaria-free by 2021. It aims to do this by stopping local transmission of the parasite that causes about 5 million annual cases and 2,500 deaths in the country.

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.

Edward is paid 100 kwacha ($10) for each five-day spell, during which he catches 300 to 400 mosquitoes. Scientists use his samples to analyse the density, types and human-biting behaviour of the female anopheles mosquito that spreads malaria.

DRUG THERAPY

In India, malaria causes 13 million infections and 24,000 deaths, according to World Health Organisation estimates. In India, 80% of malaria cases occur within the 20% of the country’s population that lives in 200 high-risk districts; these districts are showing a steady increase in p falciparum infection.

A 2016 study by the Indian Council of Medical Research’s Regional Medical Research Centre in Dibrugarh, Assam, found p falciparum infection rates as high as 84.44% in the population surveyed, followed by p vivax in 10.56% of people, and mixed infections (p falciparum and p vivax) in 5% of the population surveyed. Among the p falciparum cases, 38.16% of people were asymptomatic.

Mass drug administration of a prophylactic medicine helps stop malaria transmission even when it is undiagnosed or asymptomatic. Edward, for one, was given a tablet of the drug deltaprim as a prophylactic to prevent infection before he started his project of being mosquito dinner.

Like him, about 271,000 people in Zambia’s southern province will receive MDA in two phases this month and next, at the start of the rainy reason, in a campaign-style intervention.

“Health workers go door-to-door in designated areas within a short time to clear infections that may not be picked up by diagnostic tests with limited sensitivity,” says Dr Owen Malawo, environmental health officer and focal officer for malaria.

Of course, nothing can prevent the itch from the bite, but that doesn’t bother Edward. “I’m not itchy because I’m very fast. I catch them before they can bite me,” he says. Edward last had malaria three years ago. “I’ve not had malaria since I started this volunteer work in 2015,” he says.

If Zambia’s efforts to become malaria-free stay on track, neither will millions of others.