Sero-epidemiological evaluation of changes in Plasmodium falciparum and Plasmodium vivax transmission patterns over the rainy season in Cambodia

Malaria Journal

Research

Michael Theisen¹  Irene S Soares²  Nico Speybroeck³  Kristel Lemmens⁴  Annette Erhart⁴  Filip Claes⁴  Jackie Cook⁴  Marc Coosemans⁴  Umberto D'Alessandro⁵  Heng Somony⁶  Tho Sochanta⁶  Mao Sokny⁶ 

[1] Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark;Departamento de Análises Clínicas e Toxicológicas, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, São Paulo State, Brazil;Ecole de santé publique, Université Catholique de Louvain, Clos Chapelle-aux-Champs, 1200, Brussels, Belgium;Institute of Tropical Medicine, Nationalestraat 155, 2000, Antwerp, Belgium;Institute of Tropical Medicine, Nationalestraat 155, 2000, Antwerp, Belgium;Disease Control and Elimination, Medical Research Council Unit, Fajara, The Gambia;Parasitology and Entomology, National Center for Malaria Control, Phnom Penh, Cambodia;

关键词: Malaria;    Serology;    Classification and regression tree;    Elimination;    Cambodia;   

DOI  :  10.1186/1475-2875-11-86

 received in 2012-01-27, accepted in 2012-03-25,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundIn Cambodia, malaria transmission is low and most cases occur in forested areas. Sero-epidemiological techniques can be used to identify both areas of ongoing transmission and high-risk groups to be targeted by control interventions. This study utilizes repeated cross-sectional data to assess the risk of being malaria sero-positive at two consecutive time points during the rainy season and investigates who is most likely to sero-convert over the transmission season.MethodsIn 2005, two cross-sectional surveys, one in the middle and the other at the end of the malaria transmission season, were carried out in two ecologically distinct regions in Cambodia. Parasitological and serological data were collected in four districts. Antibodies to Plasmodium falciparum Glutamate Rich Protein (GLURP) and Plasmodium vivax Merozoite Surface Protein-119 (MSP-119) were detected using Enzyme Linked Immunosorbent Assay (ELISA). The force of infection was estimated using a simple catalytic model fitted using maximum likelihood methods. Risks for sero-converting during the rainy season were analysed using the Classification and Regression Tree (CART) method.ResultsA total of 804 individuals participating in both surveys were analysed. The overall parasite prevalence was low (4.6% and 2.0% for P. falciparum and 7.9% and 6.0% for P. vivax in August and November respectively). P. falciparum force of infection was higher in the eastern region and increased between August and November, whilst P. vivax force of infection was higher in the western region and remained similar in both surveys. In the western region, malaria transmission changed very little across the season (for both species). CART analysis for P. falciparum in the east highlighted age, ethnicity, village of residence and forest work as important predictors for malaria exposure during the rainy season. Adults were more likely to increase their antibody responses to P. falciparum during the transmission season than children, whilst members of the Charay ethnic group demonstrated the largest increases.DiscussionIn areas of low transmission intensity, such as in Cambodia, the analysis of longitudinal serological data enables a sensitive evaluation of transmission dynamics. Consecutive serological surveys allow an insight into spatio-temporal patterns of malaria transmission. The use of CART enabled multiple interactions to be accounted for simultaneously and permitted risk factors for exposure to be clearly identified.

【 授权许可】

CC BY   
© Cook et al; licensee BioMed Central Ltd. 2012