DDT resistance in Anopheles gambiae declines with mosquito age

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 new...

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Bibliographic Details
Published inMedical and veterinary entomology Vol. 5; no. 3; pp. 261 - 265
Main Authors Lines, J.D, Nassor, N.S
Format Journal Article
LanguageEnglish
Published England 01.07.1991
Subjects
Age Factors
aging
Animals
Anopheles - genetics
Anopheles gambiae
DDT
DDT (pesticide)
disease vectors
Female
insecticide resistance
Insecticide Resistance - genetics
malaria
Male
mortality
Sex Factors
Tanzania
Zanzibar
Tanzania
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Summary: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.
ISSN:0269-283X
1365-2915
DOI:10.1111/j.1365-2915.1991.tb00550.x