Blood Acquisition and Processing by Three Anopheles (Diptera: Culicidae) Species with Different Innate Susceptibilities to Plasmodium falciparum

Anopheles freeborni Aitken, An. gambiae Giles, and An. albimanus Weidemann exhibit excellent, good, and poor susceptibility to Plasmodium falciparum Welch, respectively. To determine why they differ, 5 variables relating to blood-feeding behavior and 10 variables associated with bloodmeal processing were evaluated for each species. The 3 Anopheles species did not differ in their probing behavior, but An. gambiae took 1.7 times longer to complete engorgement than either An. freeborni or An. albimanus. No interspecific differences were seen in patterns of prediuresis, blood compaction time, midgut pH, bloodmeal clearance, ovarian development, and peritrophic matrix formation. In prediuretic fluid and in blood obtained from midguts soon after mosquito feeding, erythrocytes were agglutinated heavily in An. albimanus, agglutinated moderately in An. freeborni, and unagglutinated in An. gambiae. Erythrocyte hemolysis was greatest in An. gambiae. The significant differences in patterns of blood-feeding behavior and bloodmeal processing among the 3 Anopheles species did not adequately explain interspecific differences in susceptibility to P. falciparum. Therefore, the primary mosquito-related determinants of sporogonic development may operate after bloodmeal processing, and during or after the ookinete-to-oocyst developmental transition.