Studies on multiple feeding by Anopheles gambiae s.l. in a Sudan savanna area of north Nigeria.

The detection of haptoglobins in Anopheles gambiae s.l. has been used to obtain an estimate of the incidence of multiple feeding for the village of Barmawa, Garki District, Kano State, Nigeria. The results indicated that the incidence of multiple feeding was approximately 10% but problems were encountered by the high incidence of ahaptoglobinaemia in the population. In four villages in Garki District the incidence of ahaptoglobinaemia varied between 65 and 76% while in young children and personnel under constant malaria chemoprophylaxis it was less than 30%. A strong correlation between ahaptoglobinaemia and malaria infections was seen. The results show evidence of selection of hosts by mosquitoes at Barmawa although this does not necessarily imply a preference per se. The results provide evidence of movement of blood-fed mosquitoes, between houses and from houses to resting sites.

The impact of propoxur on Anopheles gambiae s.1. and some other anopheline populations, and its relationship with some pre-spraying variables.

A significant and stable difference in the residual night-biting collection (NBC, observed/expected) of A. gambiae s.l. was observed among different villages of the West African savannah when sprayed for 2 years with propoxur. The residual mosquito density of a given village was positively associated with some of its pre-spraying characteristics: the NBC/PSC (pyrethrum spray collections) ratio, the median biting hour, and possibly the proportion of species B. It was not significantly associated with several other pre-spraying characteristics (absolute mosquito density, the ratios between NBC indoors and NBC outdoors, between ETC (exit-trap collections) and PSC, between fed and gravid in the PSC or ETC, between males and females in the PSC), and was not associated with variations in recorded coverage, with latitude, or with distance from unsprayed villages.In a comparison between A. gambiae s.l., A. funestus, and A. pharoensis, the residual NBC (observed/expected) was positively associated with the pre-spraying NBC/PSC ratio, and was negatively associated with the median biting hour.The pre-spraying NBC/PSC ratio thus appears to be a predictor of the variation, between villages or species, in the reduction of the NBC by residual spraying, and may assist in forecasting the effect of a residual insecticide. The limitations of any absolute prediction must, however, be kept in mind.