Evaluation of malaria transmission intensity using antibody responses to Plasmodium falciparum merozoite surface protein-119 after vector control in western Kenya
The scale up of malaria control strategies like insecticide-treated bednets (ITNs) and indoor residual spraying (IRS) have reduced malaria cases and deaths in endemic countries. However, as the common methods of assessing transmission intensity are imprecise and unreliable, there is need to evaluate better alternatives. Serum from 5,839 participants collected during cross-sectional surveys conducted before and after vector control were tested for anti-MSP-119 immunoglobulin G antibodies by enzyme-linked immunosorbent assay (ELISA). The prevalence of antibodies to P. falciparum MSP-119 were significantly reduced in the ITNs+IRS district from 60.5 % (95% CI: 57.7 - 62.8) to 48.7% (95% CI: 44.9 - 49.5) after the intervention. In contrast, there was only marginal reduction in sero-prevalence in the control ITNs+No-IRS district, from 48.3% (95% CI: 44.5 - 51.0) to 47.2% (95% CI: 46.1 - 50.7). There was a reduction in the age-specific sero-conversion rates from λ = 0.1272 to λ = 0.0571 in ITNs+IRS district and from λ = 0.1070 to λ = 0.0607 in the ITNs+No-IRS district at the two time points. Parasite prevalence reduced from 8.6% (95% CI: 7.2 - 10.1) to 6.9% (95% CI: 5.8 - 8.2) in the ITNs+IRS district following the intervention. In contrast, it increased significantly in ITNs+No-IRS district from 10.4 % (95% CI: 8.5 - 12.5) at baseline to 20.4% (95% CI: 18.5 - 22.3) at the second survey. This study validates the use of antibody responses to MSP-119 to monitor and evaluate the effectiveness of malaria control interventions in malaria endemic areas.