Danger: Plasmodium Crossing
It’s not easy to study and prevent malaria transmission because people are always on the move.
From home to work, or village to village, or country to country, they can pick up and carry the Plasmodium parasite. Traditional surveys often fail because they capture only what people remember and care to share. And public health programs often end abruptly at national borders not recognized by Anopheles mosquitoes. All this leads to glaring information gaps and sets the stage for malaria’s resurgence. Cross-border foot traffic, in particular, can reignite epidemics.
How big is this threat? And how can it be prevented? These are issues epidemiologist William Moss, MD, MPH, wants to investigate at three NIH-funded sites in sub-Saharan Africa that belong to the International Centers of Excellence for Malaria Research. Each site has a distinctive history that’s influenced by the presence—or absence—of cross-border foot traffic.
Recently, a tiny pocket of rural Zambia lit up with GPS signals. Each belonged to a community member going about everyday activities with a wristwatch-like GPS device in tow. Moss remembers how cautiously his colleagues approached study participants about the project. “It turns out that they thought it was really cool to wear [the devices],” Moss says. Before long, other people were asking to wear a bracelet. It was an auspicious start to a series of studies Moss plans to conduct, exploring how both small- and large-scale human movements impact malaria prevention efforts.
The GPS study is being run out of Choma District, a region in southern Zambia where recent antimalaria efforts have been successful. Yet even here, transmission hotspots remain, threatening to reverse the region’s gains. By tracking participants’ daily routines, and then overlaying them on a malaria risk map, Moss and his colleagues hope to discover how local travel can promote hotspots.
The program’s second site, Mutasa District, lies on Zimbabwe’s eastern border with Mozambique.
Family ties transcend these political boundaries, and cross-border trips are second nature to residents. For 40 years, public health programs in Zimbabwe loosened malaria’s grip. But since the programs ended in 1990, malaria’s made a comeback. Although cross-border transmission is frequently blamed, no one really knows if it’s playing a major role in the area. Using samples from 2012 and onward, Moss and colleagues plan to genotype the parasites found in patients, distinguishing “local” parasites from “imported” ones. Their results could benefit other border regions attempting to sustain public health gains in the face of dwindling budgets.
The third NIH-funded research site, in northern Zambia, also lies on an international border—this time with the Democratic Republic of Congo (DRC). For years, political instability has led the international community to steer clear of the DRC, leaving Africa’s fourth most populous country to fight malaria largely on its own. Despite the country’s violent reputation, Moss envisions creating a sister research program in the DRC to share ideas and information. Moss traveled with Peter Agre, MD, director of the Johns Hopkins Malaria Research Institute, to the DRC in February 2014. They found the country’s health minister and counterparts at Kinshasa’s Congo Protestant University eager to collaborate. Now the issue is finding funding for a DRC site. Moss is hopeful. “I think everyone recognizes that malaria can’t be controlled in sub-Saharan Africa without addressing malaria in the DRC. It’s a place where there are huge needs but also huge opportunities.”