A High Incidence of Dieldrin-resistance in Anopheles gambiae Giles from an Unsprayed Area in Northern Nigeria

Abstract

IN the course of recent investigations in the northern Guinea savannah of Nigeria on the ecology¹ of Anopheles gambiae Giles and A. funestus Giles and on their behaviour in huts sprayed with insecticides², determinations were made of the susceptibility of both species to DDT and to dieldrin in a area near the town of Kaduna. Apart from very small-scale trials in which a total of 8 village huts were sprayed with DDT and a mixture of DDT and malathion, and apart from the fairly regular use of DDT (but not dieldrin or BHC) as a larvicide on streams in the township of Kaduna, the whole of the northern Guinea savannah can be considered an unsprayed area. The nearest area receiving regular insecticidal house-spraying is the Western Sokoto area, about 200 miles north-west, where DDT has been used since 1957. Prior to this both BHC and dieldrin had been used and dieldrin-resistance in A. gambiae shown to be prevalent from 1955³. Dieldrin-resistance was also found in A. gambiae in 1956⁴ in the township of Kano, some 150 miles north-east of Kaduna, and was attributed to the use of BHC mainly for agricultural purposes.