Plasmodium falciparum sporozoites increase feeding-associated mortality oftheir mosquito hosts Anopheles gambiae s.l.

There is some evidence that pathology induced by heavy malaria infections ( many oocysts) increases mortality of infected mosquitoes. However, there is little or no published evidence that documented changes in feeding behavio ur associated with malaria infection also contribute to higher mortality of infected mosquitoes relative to uninfected individuals. We show here for t he first time that, in a natural situation, infection by the sporozoites of the malaria parasite Plasmodium falciparum significantly reduced survival of blood-feeding Anopheles gambiae, the major vector of malaria in sub-Saha ran Africa. To estimate feeding-associated mortality of infected mosquitoes , we compared the percentage of sporozoite infection in host-seeking mosqui toes caught before and after feeding. The infection rate was 12% for mosqui toes caught during the night as they were entering a tent to feed; however, only 7.5 % of the surviving members of the same cohort caught after they h ad had the opportunity to feed were infected. Thus, Plasmodium falciparum s porozoites increased the probability of dying during the night-time feeding period by 37.5 %. The increase in mortality was probably due to decreased efficiency in obtaining blood and by increased feeding activity of the spor ozoite-infected mosquitoes that elicited a greater degree of defensive beha viour of hosts under attack.