Detection of antibodies against the CB9 to ICB10 region of merozoite surface protein-1 of Plasmodium vivax among the inhabitants in epidemic areas

BACKGROUND: The purpose of this study was to examine the usefulness of the conserved block 9 (CB9) to interspecies conserved block (ICB10) region of Plasmodium vivax merozoite surface protein-1 (MSP-1 (ICB910)) as a serodiagnostic tool for understanding malaria transmission. METHODS: Antibody titre in the blood samples collected from the inhabitants of Gimpo city, Paju city and Yeoncheon county of Gyeonggi Province, as well as Cheorwon county of Gangwon Province, South Korea were determined by enzyme-linked immunosorbent assay (ELISA). Microscopic examination was performed to identify malarial parasites. RESULTS: MSP-1(ICB910) is encoded by a 1,212-bp sequence, which produced a recombinant protein with a molecular weight of approximately 46 kDa. Antibody titres in 1,774 blood samples were determined with the help of ELISA using purified recombinant MSP-1(ICB910). The overall ELISA-positive rate was 8.08% (n = 146). The annual parasite incidences (APIs) in the regions where the blood sampling was carried out gradually decreased from 2004 to 2005 (1.09 and 0.80, respectively). Yeoncheon county had the highest ELISA-positive rate (10.20%, 46/451). Yeoncheon county also had the highest API both in 2004 and 2005, followed by Cheorwon county, Paju city and Gimpo city. CONCLUSIONS: The MSP-1 (ICB910)-ELISA-positive rates were closely related to API in the geographic areas studied. These results suggest that sero-epidemiological studies employing MSP-1 (ICB910)-ELISA may be helpful in estimating the prevalence of malaria in certain geographic areas. MSP-1(ICB910)-ELISA can be effectively used to establish and evaluate malaria control and eradication programmes in the affected areas.