Rapid assessment of malaria transmission using age-specific sero-conversion rates

Laveta Stewart, Roly Gosling, Jamie Griffin, Samwel Gesase, Joseph Campo, Ramadan Hashim, Paul Masika, Jacklin Mosha, Teun Bousema, Seif Shekalaghe, Jackie Cook, Patrick Corran, Azra Ghani, Eleanor M. Riley, Chris Drakeley

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Malaria transmission intensity is a crucial determinant of malarial disease burden and its measurement can help to define health priorities. Rapid, local estimates of transmission are required to focus resources better but current entomological and parasitological methods for estimating transmission intensity are limited in this respect. An alternative is determination of antimalarial antibody age-specific sero-prevalence to estimate sero-conversion rates (SCR), which have been shown to correlate with transmission intensity. This study evaluated SCR generated from samples collected from health facility attendees as a tool for a rapid assessment of malaria transmission intensity. Methodology and Principal Findings: The study was conducted in north east Tanzania. Antibodies to Plasmodium falciparum merozoite antigens MSP-119 and AMA-1 were measured by indirect ELISA. Age-specific antibody prevalence was analysed using a catalytic conversion model based on maximum likelihood to generate SCR. A pilot study, conducted near Moshi, found SCRs for AMA-1 were highly comparable between samples collected from individuals in a conventional cross-sectional survey and those collected from attendees at a local health facility. For the main study, 3885 individuals attending village health facilities in Korogwe and Same districts were recruited. Both malaria parasite prevalence and sero-positivity were higher in Korogwe than in Same. MSP-119 and AMA-1 SCR rates for Korogwe villages ranged from 0.03 to 0.06 and 0.07 to 0.21 respectively. In Same district there was evidence of a recent reduction in transmission, with SCR among those born since 1998 [MSP-119 0.002 to 0.008 and AMA-1 0.005 to 0.014] being 5 to 10 fold lower than among individuals born prior to 1998 [MSP-119 0.02 to 0.04 and AMA-1 0.04 to 0.13]. Current health facility specific estimates of SCR showed good correlations with malaria incidence rates in infants in a contemporaneous clinical trial (MSP-119 r2 = 0.78, p<0.01 & AMA-1 r2 = 0.91, p<0.001). Conclusions: SCRs generated from age-specific anti-malarial antibody prevalence data collected via health facility surveys were robust and credible. Analysis of SCR allowed detection of a recent drop in malaria transmission in line with recent data from other areas in the region. This health facility-based approach represents a potential tool for rapid assessment of recent trends in malaria transmission intensity, generating valuable data for local and national malaria control programs to target, monitor and evaluate their control strategies.

Original languageEnglish (US)
Article numbere6083
JournalPloS one
Volume4
Issue number6
DOIs
StatePublished - Jun 29 2009

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

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