Filaria vector competence of some Anopheles species

The filaria vector competence of Anopheles stephensi was compared with Brugia-susceptible Aedes aegypti Liverpool strain, An. gambiae Badagry Lagos strain and An. dirus Perlis Malaysia strain. An. stephensi ingested more Brugia pahangi microfilariae, had the highest infectivity rate and yielded more infective mosquitoes than the other two anopheline species. The overall vector competence of An. stephensi was 0.13 times that of Ae. aegypti, 0.62 times that of An. gambiae and 2.17 times that of An. dirus. However, heavy mortality among infected An. stephensi in the present investigation indicates that the filaria vectorial capacity of the mosquito might be limited epidemiologically. The relationship between filaria vector competence and mosquito foregut armature is discussed. It was observed that the relative vector competence of the three anopheline species tested was in the same order as their relative degrees of armature elaboration. The converse would be expected if foregut armatures really give partial protection to the mosquitoes against filarial infection. It is suggested that high host microfilariae density favours larval survival proportional to the degree of armature development in Anopheles (Cellia) species.