Dr. Gerry F. Killeen
Vector control with long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), accounts for most of the unprecedented malaria burden reductions achieved in Tanzania and elsewhere across Africa over the past decade. While these interventions are highly effective, they are however insufficient to eliminate malaria transmission for a number of reasons.
First, these current front-line vector control technologies have several practical operational limitations, not least of which are cost and the fact that they only directly protect people when they are indoors or asleep.
Second, some important mosquito species avoid contact with insecticides delivered in this way, by attacking people outdoors, resting outdoors, or feeding upon animals.
Third, because of safety and cost limitations, it is currently impractical to use more than one insecticide at a time with these delivery methods, so mosquitoes find it easy to adapt by becoming tolerant to the insecticides used. Growing resistance to available insecticides is therefore already undermining the impacts of LLINs and IRS upon malaria transmission.
Progress towards elimination of malaria has therefore slowed recently, and only limited further progress can be realistically expected in the years ahead if LLINs and IRS remain the only widely-used vector control tools.
So while LLINs and IRS have had massive impacts upon malaria disease burden, and restored confidence in vector control generally, much more can and should be done to supplemented or even replace these approached with better methods over the longer term. In recent years, the Ifakara Health Institute has led the way in developing and evaluating of such additional malaria vector control options.
Mosquito control in America, Europe and Australia is predominantly achieved with a combination of long-standing high coverage with mosquito-proofed housing and environmental management, supplemented with pro-active, large-scale insecticide applications to larval habitats and outdoor spaces that kill off entire vector populations.
These more aggressive, area-wide population suppression practices are specifically tailored to local conditions by decentralized mosquito abatement programmes, which are governed, funded and managed at local level.
The Ifakara Health Institute (IHI), in partnership with the Ministry of Health, Community Development, Gender, Elderly and Children, as well as the district and city councils of Dar es Salaam, have previously developed effective management and implementation structures for routine application of environmentally-friendly biological insecticides that kill mosquitoes while they are still larvae living in water bodies.
These practical municipal systems for applying insecticide application to water bodies where mosquitoes breed were successful scaled up across the city, resulting in reductions of malaria prevalence by 74%. Furthermore, these delivery mechanisms could be readily adapted to a range of other available vector control methods that are widely used elsewhere, but need sustainable systems for routine, pro-active application by dedicated teams of technical specialists.
Furthermore, a number of new malaria vector control technologies have been pioneered at IHI. These re-purposed and emerging technologies target mosquitoes when they enter houses, feed outdoors, attack livestock, feed on sugar or aggregate into mating swarms, and all these options could well be developed into practical vector control tools for nation-wide use within the decade ahead.
Many of these technologies, such as repellent emanators, insecticide-treated clothes, attractive toxic sugar baits, insecticide treatments for livestock, mosquito-proofed housing and housing modifications that kill mosquitoes trying to enter them, could be delivered directly to individuals and households through existing distribution systems for LLINs and IRS. These approaches could therefore be scaled up relatively easily and rapidly once these technologies have been optimized and proven effective in representative rural and urban settings.
On this year’s World Malaria Day, the Ifakara Health Institute is proud to advance the ongoing development, refinement and evaluation of this new second generation of malaria vector control tools for Africa.
As an institute, we are committed to the innovation, development and evaluation processes required to make these second generation vector control approaches available to national programmes in Tanzania and beyond, and to bring the ambition of malaria elimination feasibly within our grasp.
Dr Killeen leads projects to develop new Transfluthrin Emanators for protecting against outdoor mosquito bites and Insecticide-Treated Eave Baffles for killing house-entering mosquitoes. He has been based at the Ifakara Health Institute (IHI) in Tanzania for the last 13 years, during which time he established the Environmental Health and Ecological Sciences Thematic Group.