KAMPALA, Uganda — Sometimes you have to breed mosquitoes in order to kill them.
In Uganda, where the mosquito-borne malaria parasite is the country’s leading cause of death, the health ministry must fight on multiple fronts to protect the population. It tests pregnant women for the disease, supplies local health centers with the anti-malarial drug Coartem, and with the support of the Global Fund and USAID, is working on an ambitious campaign to distribute 21 million insecticide-treated bed nets across the country. It has also set up a laboratory in the capital, Kampala, where government scientists breed the tiny bloodsuckers by the thousands.
Their mission: to test the latest weapons in the battle against malaria against the live fire of contact with actual mosquitoes.
“They are very tricky animals, by the way,” said Dr. Myers Lugemwa, the deputy program manager for Uganda’s Malaria Control Programme. Given time to adapt, he said, “they can resist anything.”
The life of Uganda’s experimental mosquitoes begin in an insectary within the Vector Control Division of the health ministry. Fed on glucose and the blood of luckless rabbits, mother mosquitoes lay eggs that, upon reaching maturity, are quickly commandeered for experiments.
When I visited the mosquito labs last Thursday, researchers were in the midst of testing the PermaNet 3.0, a brand of mosquito net that will be used in the national distribution campaign. The effort aims to provide one bed net for every two people in Uganda. Although the experiment is unlikely to determine which nets are distributed in the current campaign – most of which have been procured already – they could shape health ministry policy in the future.
The scientists allowed me to observe their tests comparing the lethality of the PermaNet 3.0 with the more widely used PermaNet 2.0. Their technique was notable for the method in which the scientists captured and transported the live mosquitoes used in the experiment.
The experiment worked like this: Hundreds of mosquitoes buzzed inside a mesh cage in the laboratory. A researcher, Daniel Bakabulindi, approached the cage with a device called an aspirator, made from a rubber tube connected to a thin glass pipe. He introduced the end of the glass pipe into the cage with the mosquitoes.
Bakabulindi then placed the rubber tube to his lips and inhaled – sucking a mosquito into the aspirator.
He repeated the process five times, capturing five insects. The aspirator held the insects in the glass pipe so that Bakabulindi would not inhale a mouthful of agitated mosquitoes.
Covering the glass pipe so that the mosquitoes would not escape, Bakabulindi then carried the aspirator to a row of clear plastic cones at the other end of the laboratory. Each cone was set on top of a section of the Permanet 3.0, so the mosquitoes would be forced to land on it. Bakabulindi inserted the aspirator’s glass tube into the top of the cone and exhaled, blowing the mosquitoes into the cone.
He then covered the cone with cotton and left the mosquitoes inside for three minutes – a duration chosen to approximate the average length of time a mosquito spends on a bed net.
Some of the mosquitoes began to fall from the air. “They are quiet now,” said Lugemwa, the Malaria Control Programme deputy manager and the study’s principal investigator. “I think they are beginning to feel the danger.”
But others continued to fly energetically inside the cone. Lugemwa said that the insecticide in the net did not act instantly, but that it should eventually kill all the mosquitoes exposed to it. The Permanet 3.0 differs from the Permanet 2.0 in that in addition to the insecticide deltamethrine, it is also treated with a synergist, Piperonyl Butoxide, intended to increase its potency.
“Laboratory tests have shown that it has done better [than Permanet 2.0] in the laboratory,” Lugemwa said. But he still wanted to test how the newer brand performed with live mosquitoes in Uganda, under conditions as close as possible to those in the field.
The final results would come from comparing the length of time, and the consistency, in which the net killed the mosquitoes. After three minutes of exposure, Bakabulindi aspirated the mosquitoes back out of the plastic cone. He then transferred them into a paper cup covered with an untreated section of netting. The cup would be checked 30 minutes, 60 minutes and 24 hours after the exposure to see how many of the mosquitoes had died.
The results would be compared with mosquitoes exposed to the Permanet 2.0 and to a control group that was left alone in a paper cup nearby.
Along one wall of the laboratory, a long countertop was covered with dozens of paper cups lined up and labeled in small clusters. The results of the experiment would not be final until the next day, when the mosquitoes could be checked 24 hours after their initial exposure.
The success of the country's 21 million net distribution campaign will depend on a multiplicity of factors: coordination between government and donors, demand among the population, and the massive logistical challenge of delivering the nets to the isolated rural villages that need them the most.
But in a good sign for the children of Uganda – and anyone else wishing for revenge against nature’s most ubiquitous bloodsuckers – the bottoms of the cups in the laboratory were littered with the bodies of silent, lifeless mosquitoes.
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