DDT resistance in Anopheles gambiae declines with mosquito age
Article first published online: 7 MAR 2008
Medical and Veterinary Entomology
Volume 5, Issue 3, pages 261–265, July 1991
How to Cite
LINES, J. D. and NASSOR, N. S. (1991), DDT resistance in Anopheles gambiae declines with mosquito age. Medical and Veterinary Entomology, 5: 261–265. doi: 10.1111/j.1365-2915.1991.tb00550.x
- Issue published online: 7 MAR 2008
- Article first published online: 7 MAR 2008
- Accepted 14 September 1990
- Anopheles gambiae;
- malaria control;
- zageing effects;
Abstract. Adult Anopheles gambiae Giles mosquitoes from Zanzibar were tested on a standard discriminating dose of DDT which reliably kills susceptible mosquitoes. Adults from wild-caught larvae reared in the laboratory, and from the F1 progeny of wild-caught adults, showed less than 5% test mortality when newly-emerged, but mortality rose with age to over 90% when they were 12–14 days old. Wild-caught mixed-age adults showed an intermediate mortality rate of 25%, close to the rate predicted from laboratory results for a fully resistant population with an age-structure typical of this species in natural conditions.
It is inferred that older, genetically resistant insects may be scored as susceptible, so that routine susceptibility tests with wild-caught adults underestimate the frequency of resistance. In Zanzibar, such tests probably helped to persuade spraying authorities to continue spraying DDT in spite of resistance. Resistance which is restricted to younger insects may nonetheless reduce the effectiveness of spraying.