Asymptomatic Plasmodium falciparum Infections as Obstacle for Malaria Elimination: A Case Study from The Gambia
PhD summary
The majority of Plasmodium falciparum malaria infections in both high and low transmission settings are asymptomatic. As asymptomatic infections typically remain untreated and could persist for long, they serve as a major source of infection to mosquitoes thereby playing a significant role in maintaining transmission and initiating seasonal malaria epidemics in the communities. Asymptomatic malaria infections are therefore a major obstacle for malaria elimination. In light of the current malaria elimination efforts, many unanswered questions about asymptomatic malaria infections have now become compelling.
Interrupting malaria transmission will require targeting the asymptomatic parasite reservoir. In most settings however, the burden of asymptomatic infection is described from routine surveys in which microscopy or rapid diagnostic tests were used as diagnostic methods. Consequently, the extent and dynamics of the submicroscopic fraction of the asymptomatic parasite reservoir is mostly unknown. Furthermore, it is currently unclear if these submicroscopic infections constitute a significant infectious reservoir. As a result, the diagnostic detection threshold required for transmission-reducing interventions to be effective is still not clearly defined. In settings where malaria elimination is the focus, there is therefore an urgent need to further understand the dynamics of submicroscopic infections and whether they substantially contribute to transmission.
Onward malaria transmission is dependent on the ingestion of gametocytes by the mosquito, yet little is known about epidemiology of gametocytes even in settings gearing for malaria elimination. Despite historical evidence of increased gametocyte prevalence following reduction in transmission intensity by control interventions, data on how current interventions deployed at the community level could influence gametocyte carriage is almost non-existen.
Within the context of declining malaria transmission of The Gambia and the drive towards elimination, this proposed doctoral work will focus on addressing some of the above highlighted knowledge gaps.