Fig. 7.

Three different experimental setups for assessing malaria transmission and TRA. In direct skin feeding assays, reared (malaria-free) mosquitoes are allowed to feed directly on blood through the skin of a naturally infected individual. Oocysts can be detected on the mosquito midgut after dissection of the mosquito. This is mostly done 7 to 9 days after feeding. The presence of oocysts confirms infection; TRA cannot be determined by direct skin feeding. In the direct membrane feeding assay (DMFA), a venous blood sample is taken from a naturally infected individual. This blood sample forms the source of gametocytes and test plasma. Samples are centrifuged, and the red blood cells that contain gametocytes are subsequently mixed with autologous plasma or malaria-naïve control serum. This mixture is kept at 37°C and offered to reared mosquitoes through a membrane, commonly Parafilm. Seven days after feeding, mosquitoes are dissected. The prevalence or density of infection in mosquitoes can be compared in pairwise comparisons between the batch of mosquitoes that fed on gametocytes in combination with control serum and the batch of mosquitoes that fed on gametocytes with autologous plasma. In the standard membrane feeding assay (SMFA), cultured gametocytes are offered to mosquitoes in the presence of test or control sera. The prevalence or density of infection in batches of mosquitoes feeding on gametocytes with control serum is compared to that in batches with test serum. In the SMFA, a large number of test sera can be tested simultaneously.