Susceptibility of the autogenous group of the Aedes scutellaris complex of mosquitoes to infection with Brugia malayi and Brugia pahangi.

Four species of mosquitoes which represent the Tonga group of the Aedes scutellaris complex (Ae. cooki, Ae. kesseli, Ae. tongae tabu and an undescribed Aedes sp. NUAOFO'OU) were tested for susceptibility to infection with Brugia malayi and B. pahangi. All tested strains were genetically fully (100%) susceptible to infection with both parasitic helminths. Higher survival of females harboring low quantities of infective larvae (1-9 L3/male) indicates a weak adaptation of the host to the parasite. Further analysis showed that in frequency distribution of infective larvae of B. malayi and B. pahangi, the most frequent category was 1-5 infective larvae per mosquito female. Distribution of te infective larvae into various parts of the mosquito body is a dynamic process. After development of L3 larvae in the thoracic muscles is completed, infective larvae migrate predominantly to the abdomen. From day 10 to 18 after an infective blood meal, L3 larvae migrate back to the thorax and head proboscis area. Low density of microfilariae in gerbils (5 mf/20 microliters) is sufficient for good infection in any of the tested mosquito species and strains. If a laboratory model with high susceptibility of mosquitoes to Brugia filarial worms is required, the autogenous group of mosquitoes of Tonga will serve as an excellent laboratory model. High susceptibility of the autogenous mosquito species to B. malayi and B. pahangi and absence of Brugian filariasis in the Polynesian region of the South Pacific is discussed.