LEUKOCYTES IN A PLASMODIUM-FALCIPARUM-INFECTED BLOOD MEAL REDUCE TRANSMISSION OF MALARIA TO ANOPHELES MOSQUITOS

Mosquitoes are infected with Plasmodium falciparum by taking a blood m eal from a gametocyte carrier. Since a mosquito takes a volume of 1 to 2 mu l, a blood meal may contain 1 x 10(4) to 3 x 10(4) leukocytes (W BC). The majority of WBC are composed of neutrophils which may phagocy tose and kill developing gametes inside the mosquito midgut, Phagocyto sis was measured in vitro by a luminol-dependent chemiluminescence (CL ) assay. In the presence of P. falciparum gametes, sera from areas of endemicity had an increased CL response compared to controls, In mosqu ito membrane feeding experiments some such sera showed a transmission reduction which was related to the presence of viable WBC, The results of this study suggest that phagocytosis of opsonized gametes inside t he mosquito midgut occurs and can contribute to a reduction in the tra nsmission of P. falciparum parasites.