Although malaria still contributes significantly to both morbidity and mortality in sub-Saharan Africa, the last decade has seen major progress in the fight against malaria as the burden has substantially decreased.
The Gambia is one of the African countries where a substantial decline has been observed. This decline is the result of the scaling-up of malaria control interventions, which include: increased availability and access to long-lasting insecticide bed nets (LLINs), integrated vector control interventions such as indoor residual spraying (IRS), strengthened case management with rapid diagnostic tests (RDTs), and artemisinin combination therapy (ACT). Despite the scaling-up of these interventions, malaria transmission, which is highly seasonal, has not been interrupted.
The contribution of infected but not sick people to maintain malaria transmission is still unclear. Being able to understand it would provide the necessary information to design new interventions aiming at interrupting malaria transmission, and thus eliminate malaria. The Malaria Programme Grant (MPG) at MRC Unit the Gambia in partnership with the National Malaria Control Programme and other Northern institutions such as the London School of Hygiene and Tropical Medicine, UK, and the Institute of Tropical Medicine, Antwerp, Belgium, seeks to understand why there are huge variations in the malaria burden between neighbouring villages.
To understand how many apparently healthy people carry a malaria infection, a nationwide malaria survey in primary schools at the end of 2012 allowed the team to select 6 locations across the country with marked heterogeneity in malaria prevalence. In each of them, a village with a relatively low malaria transmission and a neighbouring village with a high malaria transmission were identified. For the period 2013-2015, data that would help us understand the difference in malaria transmission between villages was collected. One of the factors examined was whether people who sleep outdoors are more exposed to malaria. Blood samples were collected monthly, from all residents, to identify those who are infected and understand which of these people maintain malaria transmission.
As the country aims for pre-elimination status, this requires an in-depth understanding of the current burden of Plasmodium falciparum infection. Mosquitoes were captured and data is being currently analysed to understand their biting behaviour and the influence of human behaviour on malaria transmission, both critical for targeting control efforts. The malaria team will continue to work on asymptomatic malaria infection and try to understand how they can survive within the human population from one transmission season to the other.