The aftermath of the Pare-Taveta Malaria Scheme, an experiment to control malaria in rural East Africa, provided opportunities to study the recovery of malaria vectors after the suspension of the dieldrin spraying programme. The vector status of A. gambiae did not return until some 6 years after the final round of spraying; similarly, there was a delay of almost 8 years before A. funestus was able to re-establish itself in the Mkomazi valley of South Pare. These findings are tentatively attributed to recurrent potentiation of dieldrin remaining in the mud walls of huts treated during the Scheme, which seemed to take place each year at the onset of the wet season. The opportunity was taken to examine the effects of the resurgence of malaria on local vital rates. Through the generosity of the Nuffield Foundation, a 5-year programme for the collection of vital statistics was initiated in 1961 in two communities where these rates had recently improved, coincidentally with protection from malaria transmission. A parallel series of observations were made in a neighbouring upland community, that was malaria-free. The improvements in vital rates that occurred during the Malaria Scheme in the lowland communities have been well maintained among most age-groups, at least until the end of 1966, despite the progressive return of malaria. However, there was evidence of a rising death rate during this period among young children and infants, that could be confidently connected with malaria infections. No evidence has been found to indicate that the resumption of malaria transmission was interfering with fertility in these communities.
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