Detection of an antibody against Plasmodium vivax in residents of Gimpo-si, South Korea, using an indirect fluorescent antibody test

BACKGROUND: First reemerged malaria case was reported in 1993 after two decades absent in South Korea. Thereafter, Plasmodium vivax spreads out near demilitarized zone (DMZ). This study investigated the prevalence of P. vivax after the malaria transmission season in Gimpo-si where adjacent to DMZ of South Korea. An indirect fluorescent antibody test (IFAT) was performed to evaluate anti-malaria antibodies in blood samples. METHODS: Microscopic examinations were performed to identify the presence of malaria parasites. Antibodies against P. vivax were detected using IFAT, and blood samples from antibody-positive cases were tested using a polymerase chain reaction (PCR) assay that detects malaria parasites. RESULTS: A total of 5,797 blood samples were collected from residents in Gimpo-si. The positivity rate by IFAT was 2.16% (n = 125). Yangchon-myeon (3.28%) had the highest positivity rate of the seven administrative districts tested. Positivity rates increased with age (P < 0.05). Sixteen of the IFAT positive samples (12.80%, n = 125) were positive for malaria DNA according to PCR. Blood samples with an antibody titer over 1:256 had high positivity rates in the PCR analysis (P < 0.05). CONCLUSIONS: These results indicate that antibody titers obtained using IFAT may provide useful information about the prevalence of P. vivax in low endemic areas and could be used to detect asymptomatic patients. Finding asymptomatic patients is important in eliminating vivax malaria in South Korea.