Emergence of Japanese encephalitis virus genotype V in the Republic of Korea

<p>Abstract</p> <p>Background</p> <p>Japanese encephalitis virus (JEV) genotype V reemerged in Asia (China) in 2009 after a 57-year hiatus from the continent, thereby emphasizing a need to increase regional surveillance efforts. Genotypic characterization was performed on 19 JEV-positive mosquito pools (18 pools of <it>Culex tritaeniorhynchus </it>and 1 pool of <it>Cx. bitaeniorhynchus</it>) from a total of 64 positive pools collected from geographically different locations throughout the Republic of Korea (ROK) during 2008 and 2010.</p> <p>Findings</p> <p>Two regions of the JEV genome were sequenced from 19 pools; the envelope gene and the nonstructural protein 5 (NS5)/3'-untranslated region (UTR). Eighteen pools of <it>Culex tritaeniorhynchus </it>and one pool of <it>Cx. bitaeniorhynchus </it>were positive for genotype I and genotype V, respectively. Sequence alignment of the complete E gene from <it>Cx. bitaeniorhynchus </it>showed high amino acid similarity (98.8%) to the Muar strain, characterized as the first report of genotype V, isolated from an encephalitis patient in Malaysia in 1952.</p> <p>Conclusion</p> <p>This study represents the first report of JEV genotype V in the ROK. The reemergence of genotype V in Asia (China and ROK) after more than a half-century and its discovery in <it>Cx. bitaeniorhynchus</it>, a mosquito species previously unknown to carry JEV in the ROK, emphasizes the need for enhanced JE surveillance to monitor the dynamics of JEV strains within the region. Future findings may have implications with regard to JEV vaccination/prevention strategies.</p

Comparison of PCR and microscopy for the detection of asymptomatic malaria in a <it>Plasmodium falciparum/vivax </it>endemic area in Thailand

<p>Abstract</p> <p>Objective</p> <p>The main objective of this study was to compare the performance of nested PCR with expert microscopy as a means of detecting <it>Plasmodium </it>parasites during active malaria surveillance in western Thailand.</p> <p>Methods</p> <p>The study was performed from May 2000 to April 2002 in the village of Kong Mong Tha, located in western Thailand. <it>Plasmodium vivax </it>(PV) and <it>Plasmodium falciparum </it>(PF) are the predominant parasite species in this village, followed by <it>Plasmodium malariae </it>(PM) and <it>Plasmodium ovale </it>(PO). Each month, fingerprick blood samples were taken from each participating individual and used to prepare thick and thin blood films and for PCR analysis.</p> <p>Results</p> <p>PCR was sensitive (96%) and specific (98%) for malaria at parasite densities ≥ 500/μl; however, only 18% (47/269) of <it>P. falciparum</it>- and 5% (20/390) of <it>P. vivax</it>-positive films had parasite densities this high. Performance of PCR decreased markedly at parasite densities <500/μl, with sensitivity of only 20% for <it>P. falciparum </it>and 24% for <it>P. vivax </it>at densities <100 parasites/μl.</p> <p>Conclusion</p> <p>Although PCR performance appeared poor when compared to microscopy, data indicated that the discrepancy between the two methods resulted from poor performance of microscopy at low parasite densities rather than poor performance of PCR. These data are not unusual when the diagnostic method being evaluated is more sensitive than the reference method. PCR appears to be a useful method for detecting <it>Plasmodium </it>parasites during active malaria surveillance in Thailand.</p