Microsatellite DNA Analysis Revealed a Drastic Genetic Change of Plasmodium vivax Population in the Republic of Korea During 2002 and 2003

Abstract

Background

Vivax malaria was successfully eliminated in the Republic of Korea (South Korea) in the late 1970s, but it was found to have re-emerged from 1993. In order to control malaria and evaluate the effectiveness of malaria controls, it is important to develop a spatiotemporal understanding of the genetic structure of the parasite population. Here, we estimated the population structure and temporal dynamics of the transmission of Plasmodium vivax in South Korea by analyzing microsatellite DNA markers of the parasite.

Methodology/Principal Findings

We analyzed 14 microsatellite DNA loci of the P. vivax genome from 163 South Korean isolates collected from 1994 to 2008. Allelic data were used to analyze linkage disequilibrium (LD), genetic differentiation and population structure, in order to make a detailed estimate of temporal change in the parasite population. The LD analysis showed a gradual decrease in LD levels, while the levels of genetic differentiation between successive years and analysis of the population structure based on the Bayesian approach suggested that a drastic genetic change occurred in the South Korean population during 2002 and 2003.

Conclusions/Significance

Although relapse and asymptomatic parasite carriage might influence the population structure to some extent, our results suggested the continual introduction of P. vivax into South Korea through other parasite population sources. One possible source, particularly during 2002 and 2003, is North Korea. Molecular epidemiology using microsatellite DNA of the P. vivax population is effective for assessing the population structure and temporal dynamics of parasite transmission; information that can assist in the elimination of vivax malaria in endemic areas.

Author Summary

Vivax malaria is widely prevalent, predominantly in Asia and South America. There were 390 million cases reported in 2009. Worldwide, in the same year, 2.85 billion people were at risk of infection. Plasmodium vivax is not limited to tropical and subtropical regions; it also appears in temperate areas. We previously examined the characteristics of P. vivax in South Korea, a temperate area, temporally, using 10 microsatellite DNA (a short tandem repeat DNA sequence) in the parasite genome and found the population to have low genetic diversity and a low recombination rate in comparison to tropical areas. In the present study, we examine the successive changes of the South Korean populations from 1994 to 2008, and the reasons for the lack of success in eliminating vivax malaria in this country. We found that, in spite of a low recombination rate, outbreeding between different genotypes seemed to increase gradually, and that the genetic composition of the population drastically changed during 2002 and 2003. This suggests that the parasite is continually introduced from other populations, probably from North Korea. The present study also demonstrated the utility of polymorphic DNA markers of P. vivax for the estimation of the transmission situation in endemic areas.