Study of the genetic discrimination between imported and autochthonous cases of malaria in South Korea.

There has been a great increase of Plasmodium vivax incidences in the Republic of Korea and the genetic diversity of the parasite became more complex with the rapid dissemination of newly introduced genotypes. Surveillance of imported malaria is very important, but there is no good way to determine imported vs. internal cases. In this study, we characterized imported vivax cases, analyzed the genetic sequence of three imported vivax malaria cases for the merozoite surface protein-1 (MSP-1) and circumsporozoite protein (CSP) genes, and clearly discriminated an imported vivax case that was misdiagnosed as indigenous by genetic analysis. PCR reaction for the merozoite surface protein-1 (MSP-1) and circumsporozoite protein (CSP) genes from three imported vivax cases were amplified and sequenced. The genetic variations were compared with a previously constructed database of South Korean isolates. The imported vivax cases showed various patterns on incubation period before onset. Most cases were from other parts of Asia. The MSP-1 gene sequence analysis of three imported cases showed that the imported cases had completely different sequences from any subtypes from Korean isolates. Case-1 and Case-2 exact match with an Indian isolate, and Case-3 had great similarity with isolates from countries neighboring Indonesia. CSP gene analysis based on the repeat patterns showed similar results that the sequences from the imported cases well matched with the patient's traveled countries and completely discriminated with indigenous cases. AMA-1 gene analysis also supported these results. We were able to clearly distinguish three imported vivax cases from indigenous by using a genetic database of Korean isolates and were able to suspect its origin by genotyping. This study demonstrated the usefulness of genetic survey on imported malaria cases.