Squashing Malaria: Advances in Research and Prevention [Slide Show]
From satellites to bacteria, researchers are searching high and low for the best tools to eradicate malaria
![Squashing Malaria: Advances in Research and Prevention [Slide Show]](https://www.scientificamerican.com/sciam/cache/file/BF500A41-5D85-495B-9EE140D325DC847E.jpg?w=590&h=393)
Squashing Malaria: Advances in Research and Prevention [Slide Show]
- MAPPING A MOVING TARGET Satellite data is now being tapped to track a number of vector-borne diseases, such as avian flu and rodent-spread hantavirus. And malaria researchers have put it to work to keep track of Plasmodium-carrying mosquitoes now, too. As Gregory Glass of Johns Hopkins Bloomberg School of Public Health joked at the summit about how he doesn't have clearance to use satellites that would allow him to see the mosquitoes (or small puddles that they breed in), the data he does get, however, is enough to help map ideal mosquito-breeding conditions.
"The ultimate goal is to identify when and where people are at risk for the disease," he said. By studying various regions and analyzing data about habitat, water, mosquitoes, infection rates, etcetera, his group has developed models to predict the locales where human infection is most likely to occur.
Given the limited resources (for prevention and treatment of malaria), such satellite mapping is helpful in pinpointing the populations at highest risk. This image, from the NASA Earth Observatory, shows extensive flooding in Kenya, which could prime the area for outbreaks of the mosquito-borne disease. NASA - NET GAINS Insecticide-treated bed nets currently are one of the most effective weapons in the war on malaria because they are physical barriers, rather than a biological or chemical obstacle that mosquitoes can mutate to overcome (short of shrinking to penetrate the weave). Years of free bed-net distribution have protected many in Africa, but still haven't gotten everyone covered.
A study published in April in Malaria Journal found that "marked inequity persists with the poorest households still experiencing the highest risk of malaria and the lowest insecticide-treated bed net coverage." Increasing free distribution promises to reach more families but it also "risks damaging what is otherwise an effective commercial market."
With an ever-present demand, the bed-net market could become a local economic booster. The cost of producing and distributing a net rated to last five years and likely to protect two sleeping children is about $10, according to an August 2009 article in Scientific American by Jeffrey Sachs, director of The Earth Institute and a professor of sustainable development and of health policy and management at Columbia University in New York City. P SKOV VESTERGAARD FRANDSEN/JH CENTER FOR COMMUNICATIONS PROGRAMS - VACCINE TRIALS Malaria, which has many strains across the globe, has proved a difficult target for vaccines. Early trials in the 1980s and 1990s of the vaccine SPf66 saw diminishing returns, and other candidates are in testing.
Still, an effective vaccine for malaria could provide a simple eradication strategy, and one vaccine has just entered phase III clinical trials. RTS,S/AS01, made by GlaxoSmithKline and part of the nonprofit PATH Malaria Vaccine Initiative, is now being tested in seven African countries and has already enrolled 5,000 children. Research on RTS,S began some 20 years ago in Belgium, and early testing was conducted in the U.S. in the 1990s. RTS,S works by inducing an antibody response and is being packaged with a hepatitis B antigen in hopes of protecting individuals from both infections. If the phase III trial goes according to plan the vaccine could be ready for regulatory approval in three years, which means shots could start going out before 2014. Pictured here is the first child to be vaccinated in the phase III RTS,S trials, photographed in Tanzania. DAVE POLAND/PATH MALARIA VACCINE INITIATIVE - SPIT TEST Testing for malaria has long required a blood sample, which necessitates not only trained medical personnel and sanitary equipment, but also people who are willing to have their blood drawn. "There's obviously a problem with the method we're using," Sungano Mharakurwa, scientific director of the Malaria Institute at Macha (MIAM) in Zambia, said at the summit. Testing is even tougher in communities where there is suspicion of health workers or a taboo against taking blood, he noted.
Mharakurwa is part of a team that is working to create a saliva-based test for malaria. Researchers have found that they can use genetic and antigen tests to find the infection in saliva. Mharakurwa hopes to eventually decentralize testing and train lay people locally—even mothers who could test their families—to collect samples during the off-season (when mosquitoes are dormant). By testing and treating those who are carriers off-season, fewer people will present infected blood for mosquitoes to carry when the insects emerge.
An easy and painless saliva test would also help increase the amount of screening in people who don't present symptoms of the illness. "We need screening for asymptomatic carriers," he said. A boy (pictured) gives blood for a malaria test in an Ethiopian village. BONNIE GILLESPIE/VOICES FOR A MALARIA FREE FUTURE/JH CENTER FOR COMMUNICATIONS PROGRAMS - BUILDING A BETTER MOSQUITO It only requires one broken link to break the mosquito-to-human-to-mosquito cycle of malaria transmission. "Imagine if we could cure the mosquito of malaria," said George Dimopoulos, an associate professor of molecular microbiology and immunology at the Johns Hopkins Malaria Research Institute (JHRMI), at Thursday's summit. Researchers have been working for years to find the right combination of genes to make the mosquitoes bad hosts for the parasite. Some have been trying to change the bacteria that reside in the insect's stomach to kill the invader. Others, including Dimopoulos, are working to use the mosquitoes' own immune system to resist the parasite. They have found one pathway, in particular, that would prevent the development of the protozoan.
Genetically modified mosquitoes won't be taking over the world any time soon, though. Dimopoulos noted that, "the idea is not to replace an existing population…[but] to spread genes." These so-called genetic drive-system insects are far from ready for release. "At this time it's really difficult to predict if there would be any side effects" of this genetic tinkering, he said, but later generations of lab insects might make it out for field testing.
Others, however, argue that like other blockers—such as pesticides or drugs—genetically modified mosquitoes might only serve to make the disease stronger. The transgenic Anopheles gambiae mosquito (pictured) has been made to express via red fluorescence a protein in its eyes that can spread Plasmodium, the parasite responsible for malaria. JASON L RASGON/JOHNS HOPKINS MALARIA RESEARCH INSTITUTE
