Using serological measures to monitor changes in malaria transmission in Vanuatu

• Main Authors: Clements Archie, Taleo George, Kuwahata Melissa, Iavro Jennifer, Reid Heidi, Cook Jackie, McCarthy James, Vallely Andrew, Drakeley Chris
• Format: Article
• Language: English
• Published: BMC 2010-06-01
• Series: Malaria Journal
• Online Access: http://www.malariajournal.com/content/9/1/169

<p>Abstract</p> <p>Background</p> <p>With renewed interest in malaria elimination, island environments present unique opportunities to achieve this goal. However, as transmission decreases, monitoring and evaluation programmes need increasingly sensitive tools to assess <it>Plasmodium falciparum </it>and <it>Plasmodium vivax </it>exposure. In 2009, to assess the role of serological markers in evaluating malaria transmission, a cross-sectional seroprevalence study was carried out in Tanna and Aneityum, two of the southernmost islands of the Vanuatu archipelago, areas where malaria transmission has been variably reduced over the past few decades.</p> <p>Methods</p> <p>Malaria transmission was assessed using serological markers for exposure to <it>P. falciparum </it>and <it>P. vivax</it>. Filter blood spot papers were collected from 1,249 people from Tanna, and 517 people from Aneityum to assess the prevalence of antibodies to two <it>P. falciparum </it>antigens (MSP-1₁₉and AMA-1) and two <it>P. vivax </it>antigens (MSP-1₁₉and AMA-1). Age-specific prevalence was modelled using a simple catalytic conversion model based on maximum likelihood to generate a community seroconversion rate (SCR).</p> <p>Results</p> <p>Overall seropositivity in Tanna was 9.4%, 12.4% and 16.6% to <it>P</it>. <it>falciparum </it>MSP-1₁₉, AMA-1 and Schizont Extract respectively and 12.6% and 15.0% to <it>P. vivax </it>MSP-1₁₉and AMA-1 respectively. Serological results distinguished between areas of differential dominance of either <it>P. vivax </it>or <it>P. falciparum </it>and analysis of age-stratified results showed a step in seroprevalence occurring approximately 30 years ago on both islands, indicative of a change in transmission intensity at this time. Results from Aneityum suggest that several children may have been exposed to malaria since the 2002 <it>P. vivax </it>epidemic.</p> <p>Conclusion</p> <p>Seroepidemiology can provide key information on malaria transmission for control programmes, when parasite rates are low. As Vanuatu moves closer to malaria elimination, monitoring changes in transmission intensity and identification of residual malaria foci is paramount in order to concentrate intervention efforts.</p>