Sleeping pods attached to the mosquito house in Macha, Zambia.Credit: Macha Research Trust
In tiny sleeping pods, separated from mosquitoes by a layer of mesh, human volunteers sacrifice a good night’s slumber in the name of science – to support innovative research that could turn the tide on the devastating malaria epidemic.
Connected to a large central mosquito house, or ‘flight cage’ in the remote village of Macha in southern Zambia, the unique body scents emitted by the sleeping volunteers provide data for what scientists have called “the world’s largest multi-choice smell test”, which asks why mosquitoes like some humans more than others.
The study, published in Current Biology, answered some of the questions.
The multi-faceted malaria research is a collaboration with Johns Hopkins Bloomberg School of Public Health, with scientists now leveraging the human scent findings to engineer synthetic blends of chemicals that best mimic the ones to which mosquitos are most attracted.
This new knowledge of how mosquitoes smell humans, explains Conor McMeniman, assistant professor in the Department of Molecular Biology at Johns Hopkins, can be utilised in two critical ways: “With this knowledge, we can now develop new, more effective repellents, but also potentially turn the mosquito’s sense of smell against them, by engineering synthetic blends to lure mosquitoes into traps for mass control purposes.”
Three-quarters of the 600 000 deaths from malaria each year occur in children under five, mostly in countries of sub-Saharan Africa, but also India and South-East Asia,” says Jane Carlton, director of the Johns Hopkins Malaria Research Institute.
Researcher Limonty Simubali, at work at the Macha Research Trust.Credit: Limonty Simubali
Fighting malaria is a complex challenge however, due to drug resistance in the malaria parasite, and insecticide resistance. Of particular concern, Carlton stresses, is that the invasive mosquitoes that transmit malaria, such as Anopheles stephensi, have also recently appeared in African cities, increasing urban malaria transmission.
“Humans that are most attractive to the malaria mosquito have body odour or human scent signatures that are enriched for a class of molecules called airborne carboxylic acids, and also other compounds that are produced by the bacteria that live on our skin,” explains McMeniman, the study’s lead author.
Diet, genetics and resulting physiology all play a role, along with the microbes that live on skin surfaces. But whether changes in diet can make humans less attractive to mosquitoes is an “exciting area for future research”, he adds.
Work is also continuing at the Malaria Institute to “build a better mosquito” to halt transmission of malaria through the application of cutting-edge genetic engineering. Scientists there have also developed a portable cost-effective device to determine mosquito resistance to insecticides.
Their field partners at the Macha Research Trust, as well as partners in Ethiopia and other countries outside Africa, have a critical role to play, McMeniman says. “One of our priorities is strengthening our commitment, working alongside them, to generate accelerated pipelines to take innovations from the laboratory to the field.”
“It’s very exciting for the Zambian scientists working on the project, who are not only advancing their skills, but potentially influencing policy that can move the continent closer to eliminating this major public health threat,” says researcher, Limonty Simubali, of the community-based Macha Research Trust.
Working with the hospital and the community, the trust has achieved significant improvements in health and well-being in the area. Malaria incidence in Macha has decreased by more than 95%.
For Simubali, the chance to play a role in science that could help end malaria is “an enormous privilege”. Although not one of Africa’s highest-burden malaria countries, the disease remains a significant cause of illness and death in Zambia.
“The flight cage is a unique, exciting experiment, and the collaboration has provided excellent opportunities for capacity-building that will have impacts for science in Zambia far into the future,” he says.
