a1 Ifakara Centre, Tanzania
a2 Ifakara Centre, Tanzania & Department of Public Health and Epidemiology, Swiss Tropical Institute, Basel, Switzerland
a3 Ifakara Centre, Tanzania
a4 Department of Public Health and Epidemiology, Swiss Tropical Institute, Basel, Switzerland
a5 Department of Biology, Imperial College of Science, Technology and Medicine, London, UK
a6 Department of Entomology, Wageningen Agricultural University, The Netherlands
The possibility of density dependent feeding success in the African malaria vectors Anopheles gambiae Giles (sensu lato) and A. funestus Giles was investigated by examining the gonotrophic status of mosquitoes from 423 collections made in a Tanzanian village. Up to 500 mosquitoes were caught in any single 35 minute indoor resting collection. Estimates of the total numbers of mosquitoes resting were made by removal sampling. These indicated that the efficiency of resting collections decreased with increasing mosquito population. Of 1904 mosquito blood meals tested by ELISA, 95% were of human origin. There was no decrease in the proportion of mosquitoes fully fed at high population densities and the only demonstrable avoiding action by hosts in response to high densities of mosquitoes was the increased use of bednets during the wet season. The late biting cycle of these mosquitoes precludes many other density-dependent host defence mechanisms because the hosts are asleep at the time of attack. African malaria vectors have evolved with man and perhaps their evasion of density-dependent host responses has reinforced their preference for human blood.
(Accepted September 12 1994)
c1 Dr. T Smith, Dept. Public Health & Epidemiology, Swiss Tropical Institute, PO Box, CH-4002 Basel, Switzerland.