Differential attractiveness of humans to the African malaria vector Anopheles gambiae Giles: Effects of host characteristics and parasite infection.

Introduction:

Malaria in man is caused by four species of protozoan parasites1 belonging to the genus Plasmodium. Plasmodium parasites exhibit a complex life cycle involving development through two host2 species: an insect vector3 (definitive host4) and a vertebrate species (intermediate host5). Humans serve as intermediate hosts for several Plasmodium species (P. falciparum, P. vivax, P. ovale and P. malariae) whilst female mosquitoes of the genus Anopheles serve as the definitive hosts (Figure 1). Plasmodium parasites are transmitted between humans through the periodic blood-feeding behaviour of female Anopheles mosquitoes. Thus, humans also serve as hosts for female anophelines which, in turn, constitute (temporary) ectoparasites6. The Plasmodium parasite initiates its sexual cycle of development within a freshly ingested blood meal present inside the mosquito midgut, when male and female gametocytes shed their erythrocyte membranes. Exflagellation, fertilisation and ookinete formation take place thereafter. Motile ookinetes penetrate the midgut wall and peritrophic membrane, come to lie under the basal lamina and oocysts are formed.