Studies on the Breeding Places and Control of Anopheles gambiae and A. gambiae var. melas in Coastal Districts of Sierra Leone

Abstract

The eggs of A. gambiae var. melas are distinctly different from those of typical gambiae, and it is now regarded as a distinct species, A. melas. Other workers have found that the larvae also differ, physiologically and structurally. All adults with an extra dark band on the palps—4-banded forms— are known to be melas, but those adults with normal 3-banded palps can so far only be distinguished from typical gambiae by egg characters.A. melas is now known to be an important vector of malaria in coastal districts in West Africa. In some estuarine and mangrove swamp areas it may be even more important than typical gambiae. In melas caught in Freetown estuary (mostly from Wellington village), 42 out of 1,000 glands dissected were positive, giving a sporozoite rate of 4·2 per cent. for all months of the year. The oocyst rate was 4·7 per cent., and the total infection rate was 7·8 per cent.In Freetown estuary melas is rare in Freetown itself, and in the adjoining village of Kissy, but in all other parts of the estuary is at least as important as typical gambiae. In many places it is the dominant vector. In Wellington to the east of Kissy, and on the Bullom shore which forms the north shore of the estuary, melas forms about 90 per cent. of Anophelines caught in houses.