Negligible Impact of Mass Screening and Treatment on Mesoendemic Malaria Transmission at West Timor in Eastern Indonesia: A Cluster-Randomized Trial

Abstract

Background: Mass screening and treatment (MST) aims to reduce malaria risk in communities by identifying and treating infected persons without regard to illness.

Methods: A cluster-randomized trial evaluated malaria incidence with and without MST. Clusters were randomized to 3, 2, or no MST interventions: MST3, 6 clusters (156 households/670 individuals); MST2, 5 clusters (89 households/423 individuals); and MST0, 5 clusters (174 households/777 individuals). All clusters completed the study with 14 residents withdrawing. In a cohort of 324 schoolchildren (MST3, n = 124; MST2, n = 57; MST0, n = 143) negative by microscopy at enrollment, we evaluated the incidence density of malaria during 3 months of MST and 3 months following. The MST intervention involved community-wide expert malaria microscopic screening and standard therapy with dihydroartemisinin-piperaquine and primaquine for glucose-6 phosphate dehydrogenase-normal subjects. All blood examinations included polymerase chain reaction assays, which did not guide on-site treatment.

Results: The risk ratios for incidence density of microscopically patent malaria in MST3 or MST2 relative to that in MST0 clusters were 1.00 (95% confidence interval [CI], .53-1.91) and 1.22 (95% CI, .42-3.55), respectively. Similar results were obtained with molecular analysis and species-specific (P. falciparum and P. vivax) infections. Microscopically subpatent, untreated infections accounted for 72% of those infected.

Conclusions: Two or 3 rounds of MST within 3 months did not impact the force of anopheline mosquito-borne infection in these communities. The high rate of untreated microscopically subpatent infections likely explains the observed poor impact.

Clinical trials registration: NCT01878357.

Figure 1.

Map of the study site. Abbreviation: MST, mass screening and treatment.

Figure 2.

Trial profile. Abbreviations: GPS, Global Positioning System; MST, mass screening and treatment.

Figure 3.

Malaria prevalence by microscopy and polymerase chain reaction (PCR), and Plasmodium falciparum gametocyte rate by microscopy at the cluster (A–D) and individual levels (E–H). Cluster level showed significant decrease of P. falciparum infections based on microscopic and PCR examinations at the last survey (B). Individual level demonstrated this change with PCR (F). Similarly, gametocytes of P. falciparum that was detected by microscopy demonstrated significant decrease in cluster level (C). In Plasmodium vivax infections, neither change was detected in the cluster and individual levels (D and H). The χ² test was used for individual level, and generalizing estimating equations was used for cluster level. Abbreviation: MST, mass screening and treatment.

Figure 4.

Microscopic (A–C) and polymerase chain reaction (D–F) based individual malaria incidence density of schoolchildren in all arms within 6 months. No significant difference of incidence density in all malaria, Plasmodium falciparum, and Plasmodium vivax infections between arms. Hazard ratios were estimated using Cox regression analysis. Abbreviations: CI, confidence interval; HR, hazard ratio; MST, mass screening and treatment.