Impact of indoor residual spraying of lambda-cyhalothrin on malaria prevalence and anemia in an epidemic-prone district of Muleba, north-western Tanzania.

The Government of Tanzania introduced indoor residual spraying (IRS) in Muleba district in north-western Tanzania after frequent malaria epidemics. Malaria parasitological baseline and two cross-sectional follow-up surveys were conducted in villages under the IRS program and those not under IRS to assess the impact of IRS intervention. After two rounds of IRS intervention there was a significant reduction of malaria parasitological indices in both two villages. In IRS villages overall, parasitemia prevalence was reduced by 67.2%, splenomegaly was reduced by 75.8%, whereas anemia was reduced by 50.5%. There was also a decline of malaria parasite density from 896.4 at baseline to 128.8 at second follow-up survey. Similarly, there was also a reduction of malaria parasitological indices in non-IRS villages; however, parasitological indices in IRS villages remained far below the levels in non-IRS villages. The reduction of malaria parasitological indices in non-IRS villages might have been contributed by interventions other than IRS.