Assessment of the Impact of Chlorpyrifos Resistance in Culex Quinquefasciatus on a Control Scheme

  • C. F. Curtis
  • A. Keto
  • B. D. Ramji
  • I. Iosson


A high level of resistance to chlorpyrifos has been detected in Culex quinquefasciatus larvae from Dar es Salaam. To study the impact of this resistance on the routine anti-larval spraying programme with this chemical, pit latrines, cess pits and soakage pits were examined regularly after spraying. Larvae were eliminated immediately after spraying, but in most cases they re-appeared about 2 weeks later. Bio-assays with susceptible and resistant larvae in water samples from the pits showed that in most cases there would have been sufficient insecticide residue for at least 10 weeks to kill a susceptible population, but resistant larvae could survive in the water from about 2 weeks after spraying. Chemical analysis showed that the water was toxic to resistant larvae so long as it contained about 0.02 mg/1 chlorpyrifos. These observations might have suggested that the routine spraying programme every 10 weeks would be having very little impact on the population now that resistance has evolved. However, in fact, adult densities in houses in a year with spraying on schedule were much less than in years when many sprayings were missed owing to shortage of supplies. Thus the regular spraying programme still apppears to have a beneficial effect.


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  1. Bang Y. H., Sabuni I. B. and Tonn R. T. (1975) Integrated control of urban mosquitoes in Dar es Salaam using community sanitation supplemented by larviciding. E. Afr. med. J. 52, 578–588.Google Scholar
  2. Curtis C. F. (1980) Insect traps for pit latrines. Mosq. News 40, 626–628.Google Scholar
  3. Curtis C. F. and Pasteur N. (1981) Organophosphate resistance in vector populations of the complex of Culex pipiens L. Bull. ent. Res. 71, 153–161.CrossRefGoogle Scholar
  4. Curtis C. F. and Suya T. B. (1981) Variations in cytoplasmic incompatibility properties in Tanzanian populations of Culex quinquefasciatus. Ann. trop. Med. Parasit. 75, 101–106.CrossRefGoogle Scholar
  5. Reiter P. (1978) Expanded polystyrene balls: an idea for mosquito control. Ann. trop. Med. Parasit. 72, 595–596.CrossRefGoogle Scholar
  6. Schaefer C. H. and Dupras E. F. (1970) Factors affecting the stability of Dursban in polluted waters. J. econ. Ent. 63, 701–705.CrossRefGoogle Scholar
  7. Sinègre G., Jullien J. L. and Gaven B. (1977) Acquisition progressive de la résistance au chlorpyrifos chez les larves de Culex pipiens dans le midi de la France. Parassitologia 19, 79–94.PubMedGoogle Scholar
  8. Villani F., White G. B., Curtis C. F. and Miles S. J. (1983) Inheritance and activity of some esterases associated with organophosphate resistance in mosquitoes of the complex of Culex pipiens L. Bull. ent. Res. 73, 153–166.CrossRefGoogle Scholar

Copyright information

© Pergamon Press LId 1984

Authors and Affiliations

  • C. F. Curtis
    • 1
  • A. Keto
    • 2
  • B. D. Ramji
    • 3
  • I. Iosson
    • 4
  1. 1.London School of Hygiene and Tropical MedicineLondonEngland
  2. 2.Dar es Salaam City CouncilDar es SalaamTanzania
  3. 3.Muhimbili Medical CentreDar es SalaamTanzania
  4. 4.Dow Chemical Co.NorfolkEngland

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