Mis à jour le 24/10/22

Malaria due to Plasmodium (P.) falciparum remains a major public health issue in much of the tropical and subtropical regions. In Ghana, malaria is the leading cause of morbidity and mortality in children, accounting for about 40% of all outpatient attendance at health facilities in 2017 and for 26 % of childhood deaths. Malaria related mortality has successfully been reduced in Ghana by multiple intervention strategies implemented after Ghana has committed itself to the Roll Back Malaria (RBM) initiative in 1999. However, malaria elimination may not be possible in the immediate future as the high levels of persistent asymptomatic Plasmodium carriage results in the continuous production of the transmissible sexual stage parasites (gametocytes) which in the presence of competent Anopheles vectors results in the endless spread of malaria. A thorough understanding of the human infectious reservoir and of the gametocyte formation is essential for developing interventions to be targeted to individuals who are most important for the transmission of infection to mosquitoes.

During malaria transmission, a female Anopheles mosquito picks up gametocytes from the human host in the course of a blood meal. The successful completion of the sporogonic life cycle of the parasite within the mosquito sustains malaria transmission. Factors including gametocyte prevalence and density as well as male to female gametocyte sex ratio and gametocyte infectiousness to the mosquito can interfere with the completion of the sporogonic life cycle of the parasite and enhance pathogen transmission. Mosquito saliva is known to generally increase the transmission of pathogens from the mosquito vector to the human host, however little is known about the role played by components of mosquito saliva in the transmission of Plasmodium to humans. We intend to adapt our novel ex vivo gametocyte conversion rate (GCR) assay to determine whether mosquito salivary gland extract directly or indirectly alter GCR and or gametocyte infectiousness to the mosquito. We also intend to use a natural field-based longitudinal study to identify how changes in mosquito biting rates alter gametocyte infectiousness and GCR. We will be following a cohort of adults and children to identify which age range are more at risk of serving as reservoirs for malaria transmission in Ghana as well as identify which season would be ideal to implement transmission blocking interventions. These results will be fed to the Ghana National Malaria Control Program as policy documents.

Understanding how mosquito saliva interacts with asymptomatic Plasmodium carriers could provide new insights for development of control tools to reduce malaria transmission and help achieve the goal of good health as well as malaria elimination in Ghana . Our strategy of using a combination of laboratory and field-based approaches represents an innovation that will provide useful information about this economically important disease.

Période de soutien janvier 2020 - Décembre 2022