Behaviour of Anopheles arabiensis and An. quadriannulatus sp. B mosquitoes and malaria transmission in southwestern Ethiopia

Mosquito collections were carried out in four villages of southwestern Ethiopia to determine the resting sites, host preference and sporozoite infection rate in members of the Anopheles gambiae complex in the region. Catches of mosquitoes resting indoors were carried out in three types of dwelling: houses, mixed human and cattle habitations, and cattle sheds. Polymerase chain reaction assays showed that 737 of the 800 specimens of An. Gambiae complex mosquitoes that were collected indoors were either Anopheles arabiensis (55.5 %) or An. Quadriannulatus sp. B (44.5 %). The other 63 specimens were not identifiable due to either DNA degradation or technical problems during tests. The majority of indoor-resting An. Arabiensis (74.9 %) and An. Quadriannulatus sp. B (94.8 %) were caught in cattle sheds. The proportion of An. Arabiensis captured in human dwellings, mixed habitations and cattle sheds was significantly different, indicating strong zoophilic behaviour in this malaria-vector species. The human blood index of An. Arabiensis was 7.3 % and only one specimen was positive for Plasmodium parasites, having both P. falciparum and P. vivax sporozoites and giving a sporozoite rate of 0.24 %. The proportion of An. Quadriannulatus sp. B captured in human dwellings, mixed habitations and cattle sheds was also significantly different in accordance with the known behaviour of this non-vector species which is predominantly cattle-feeding. The human blood index of An. Quadriannulatus sp. B was 1.1 % which was significantly different from that of An. Arabiensis. Positive reactions for Plasmodium circumsporozoite proteins were not observed in the An. Quadriannulatus sp. B that were tested. Very few mosquitoes were collected in pit traps, indicating that both species are not attracted to pits as outdoor resting places.