Patterns of erythrocyte digestion by bloodsucking insects: constraints on vector competence.

Two general patterns of erythrocyte digestion were observed in representative species from four insect orders. Ingested erythrocytes were hemolyzed rapidly, and blood meals remained liquefied within body lice, Pediculus humanus L. and the fleas Ctenocephalides felis (Bouché) and Xenopyslla cheopis (Rothschild). Peritrophic membrane was absent. In contrast, there was a lag time of 6-18 h before substantial degradation of erythrocytes within the blood meals of bed bugs, Cimex lectularius L.; the sand fly Phlebotomus papatasi Scopoli; and the mosquitoes Anopheles stephensi Liston and Culex pipiens L. Blood meals of sand flies and mosquitoes were clotted and surrounded by peritrophic membrane at 18-24 h after feeding. Clotting and peritrophic membrane were less pronounced in bed bugs. It is proposed that acquisition and maintenance of pathogen types (i.e., prokaryotic versus eukaryotic) within insects are constrained by the general pattern of bloodmeal processing.