• Parasites, Hosts and Diseases
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• v.44 no.4 s.140
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• pp.285-294
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• 2006

Changing patterns of the reemerging Plasmodium vivax malaria in the Republic of Korea (South Korea) during the period 1993 to 2005 are briefly analyzed with emphasis on the control measures used and the effects of meteorological and entomological factors. Data were obtained from the Communicable Diseases Monthly Reports published by the Korea Center for Disease Control and Prevention, and webpages of World Health Organization and United Nations. Meteorological data of Kangwon-do (Province) were obtained from local weather stations. After its first reemergence in 1993, the prevalence of malaria increased exponentially, peaking in 2000, and then decreased. In total, 21,419 cases were reported between 1993 and 2005 in South Korea. In North Korea, a total of 916,225 cases were reported between 1999 and 2004. The occurrence of malaria in high risk areas of South Korea was significantly (P < 0.05) correlated with the mosquito population but not with temperature and rainfall, Control programs, including early case detection and treatment, mass chemoprophylaxis of soldiers, and international financial aids to North Korea for malaria control have been instituted. The situation of the reemerging vivax malaria in the Republic of Korea is remarkably improving during the recent years, at least in part, due to the control activities undertaken in South and North Korea.

• Parasites, Hosts and Diseases
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• v.41 no.4
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• pp.203-207
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• 2003

An ELISA was developed for the diagnosis of vivax malaria using multiple stage-specific recombinant antigens of Plasmodium vivax. The DNA from the whole blood of a malaria patient was used as template to amplify the coding regions for the antigenic domains of circumsporozoite protein (CSP-1), merozoite surface protein (MSP-1), apical merozoite antigen (AMA-1), serine repeat antigen (SERA), and exported antigen (EXP-1). Each amplified DNA fragment was inserted into pQE30 plasmid to induce the expression of His-tagged protein in Escherichia coli (M15 strain) by IPTG. His-tagged proteins were purified by Ni-NTA metal-affinity chromatography and used as antigens for ELISA with patient sera that were confirmed previously by blood smear examinations. When applied to patient sera, 122 (80.3%) out of 152 vivax malaria cases reacted to at least one antigen, while no reactions were observed with 128 uninfected serum samples. We applied this ELISA to the screening of 3,262 civilian residents in endemic regions near the DMZ, which resulted in 236 positively detected (7.2%) cases. This method can be applied to serological diagnosis and mass screening in endemic regions, or can be used as a safety test for transfusion blood in endemic areas.

• Parasites, Hosts and Diseases
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• v.52 no.2
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• pp.143-149
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• 2014

To evaluate the seroprevalence against circumsporozoite protein (CSP) of Plasmodium vivax in sera of Korean patients, the central repeating domain (CRD) of CSP was cloned and analyzed. From the genomic DNA of patient's blood, 2 kinds of CSPs were identified to belong to a VK210 type, which is the dominant repeating of GDRA(D/A)GQPA, and named as PvCSPA and PvCSPB. Recombinantly expressed his-tagged PvCSPA or PvCSPB in Escherichia coli reacted well against sera of patients in western blot, with the detecting rate of 47.9% (58/121), which included 15 cases positive for PvCSPA, 6 cases positive for PvCSPB, and 37 cases for both. The mixture of PvCSPA and PvCSPB was loaded to a rapid diagnostic test kit (RDT) and applied with the same set of patient sera, which resulted in detection rates of 57.0% (69/121). When the protein sequences of PvCSPA were compared with those of P. vivax in endemic regions of India and Uganda, they were compatibly homologous to PvCSPA with minor mutations. These results suggested that the recombinant PvCSPA and PvCSPB loaded RDT may be a milestone in latent diagnosis which has been a hot issue of domestic malaria and important for radical therapy in overlapped infections with P. falciparum in tropical and subtropical areas. During the biological process of malarial infection, exposure of CSP to antigen-antibody reaction up to 57.0% is the first report in Korea.

• Parasites, Hosts and Diseases
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• v.54 no.6
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• pp.725-732
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• 2016

Plasmodium vivax produces numerous caveola-vesicle complex (CVC) structures beneath the membrane of infected erythrocytes. Recently, a member helical interspersed subtelomeric (PHIST) superfamily protein, $PcyPHIST/CVC-81_{95}$, was identified as CVCs-associated protein in Plasmodium cynomolgi and essential for survival of this parasite. Very little information has been documented to date about $PHIST/CVC-81_{95}$ protein in P. vivax. In this study, the recombinant $PvPHIST/CVC-81_{95}$ N and C termini were expressed, and immunoreactivity was assessed using confirmed vivax malaria patients sera by protein microarray. The subcellular localization of $PvPHIST/CVC-81_{95}$ N and C termini in blood stage parasites was also determined. The antigenicity of recombinant $PvPHIST/CVC-81_{95}$ N and C terminal proteins were analyzed by using serum samples from the Republic of Korea. The results showed that immunoreactivities to these proteins had 61% and 43% sensitivity and 96.9% and 93.8% specificity, respectively. The N terminal of $PvPHIST/CVC-81_{95}$ which contains transmembrane domain and export motif (PEXEL; RxLxE/Q/D) produced CVCs location throughout the erythrocytic-stage parasites. However, no fluorescence was detected with antibodies against C terminal fragment of $PvPHIST/CVC-81_{95}$. These results suggest that the $PvPHIST/CVC-81_{95}$ is localized on the CVCs and may be immunogenic in natural infection of P. vivax.

• Parasites, Hosts and Diseases
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• v.60 no.1
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• pp.15-23
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• 2022

Erythrocytes deficient in glucose-6-phosphate dehydrogenase (G6PD) is more susceptible to oxidative damage from free radical derived compounds. The hemolysis triggered by oxidative agents such as primaquine (PQ) is used for the radical treatment of hypnozoites of P. vivax. Testing of G6PD screening before malaria treatment is not a common practice in Thailand, which poses patients at risk of hemolysis. This retrospective study aimed to investigate the prevalence of G6PD in malaria patients who live in Southern Thailand. Eight hundred eighty-one malaria patients were collected for 8-year from 2012 to 2019, including 785 (89.1%) of P. vivax, 61 (6.9%) of P. falciparum, 27 (3.1%) of P. knowlesi, and 8 (0.9%) of mixed infections. The DiaPlexC genotyping kit (Asian type) and PCR-RFLP were employed to determine the G6PD variants. The result showed that 5 different types of G6PD variants were identified in 26 cases (2.9%); 12/26 (46.2%) had Mahidol (487G>A) and 11/26 (42.3%) had Viangchan (871G>A) variants, while the rest had Kaiping (1388G>A), Union (1360C>T), and Mediterranean (563C>T) variants. G6PD Songklanagarind (196T>A) variant was not found in the study. Our result did not show a significant difference in the malaria parasite densities in patients between G6PD-deficient and G6PD-normal groups. According to our findings, testing G6PD deficiency and monitoring the potential PQ toxicity in patients who receive PQ are highly recommended.

• Pediatric Infection and Vaccine
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• v.10 no.2
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• pp.200-207
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• 2003

Purpose : Malaria is known to have been eradicated for a few decades through persistent national health program in South Korea. However, malaria caused by Plasmodium vivax has started to reappear incidiously among military personnel near to DMZ since 1993. After then, the number of malarial cases have been increased abruptly year by year. We analyzed the children of indigenous malaria who were diagnosed by peripheral blood smear and malarial antibody test with regards to epidemiologic and clinical manifestations. Methods : The study 13 cases below 15 years of age, who were confirmed as vivax malaria during from January 2000 to August 2003. We retrospectively analyzed epidemiologic data, clinical manifestations, laboratory findings and therapeutic responses. Results : All of 13 cases were indigenous and tested positive for Plasmodium vivax. Of 13 patients, 9 were male and 4 were female. Mean age of onset was $9.5{\pm}3.6$ years old. Ilsan(n=9) was the most prevalent area, the most patients(n=11) were presented in summer (from June to August). A characteristic feature of periodic 3 day fever in patients with P.vivax infection was reported in only 2 among 13 cases. Thrombocytopenia was most prominent findings, which was accompanied by 12 of 13 patients and pancytopenia was appeared in 3 patients on this study. The therapeutic responses of hydroxycholoquine were very good in all cases, and abnormal laboratory findings were recovered and no relapse during follow-up period. Conclusion : Vivax malaria is indigenous in Korea near to DMZ, but recently endemic area seemed to be extended southward. Plasmodium vivax is the cause of indigenous malaria of children. As for children with high fever accompanying thrombocytopenia in endemic area of Korea, malaria must be included in differential diagnosis whether the type of fewer is periodic 3 day fever or not. Malaria antibody test is helpful as a screening test for malaria.

• Parasites, Hosts and Diseases
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• v.42 no.2
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• pp.61-66
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• 2004

The plasmepsins are the aspartic proteases of malaria parasites. Treatment of aspartic protease inhibitor inhibits hemoglobin hydrolysis and blocks the parasite development in vitro suggesting that these proteases might be exploited their potentials as antimalarial drug targets. In this study, we determined the genetic variations of the aspartic proteases of Plasmodium vivax (PvPMs) of wild isolates. Two plasmepsins (PvPM4 and PvPM5) were cloned and sequenced from 20 P. vivax Korean isolates and two imported isolates. The sequences of the enzymes were highly conserved except a small number of amino acid substitutions did not modify key residues for the function or the structure of the enzymes. The high sequence conservations between the plasmepsins from the isolates support the notion that the enzymes could be reliable targets for new antimalarial chemotherapeutics.

• Parasites, Hosts and Diseases
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• v.53 no.2
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• pp.169-175
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• 2015

The relationship between anti-Plasmodium vivax circumsporozoite protein (CSP) antibody levels and the prevalence of malaria in epidemic areas of South Korea was evaluated. Blood samples were collected from inhabitants of Gimpo-si (city), Paju-si, and Yeoncheon-gun (county) in Gyeonggi-do (province), as well as Cheorwon-gun in Gangwon-do from November to December 2004. Microscopic examinations were used to identify malaria parasites. ELISA was used to quantitate anti-circumsporozoite protein (CSP) antibodies against P. vivax. A total of 1,774 blood samples were collected. The overall CSP-ELISA-positive rate was 7.7% (n=139). The annual parasite incidences (APIs) in these areas gradually decreased from 2004 to 2005 (1.09 and 0.80, respectively). The positive rate in Gimpo (10.4%, 44/425) was the highest identified by CSP-ELISA. The highest API was found in Yeoncheon, followed by Cheorwon, Paju, and Gimpo in both years. The positive rates of CSP-ELISA were closely related to the APIs in the study areas. These results suggest that seroepidemiological studies based on CSP may be helpful in estimating the malaria prevalence in certain areas. In addition, this assay can be used to establish and evaluate malaria control and eradication programs in affected areas.

• Parasites, Hosts and Diseases
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• v.59 no.4
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• pp.415-419
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• 2021

The circumsporozoite protein (CSP) of Plasmodium spp. is a diagnostic antigen and useful biomarker for monitoring short-term/seasonal changes to malaria transmission. Using P. vivax CSP antibody ELISA, epidemiological characteristics were analyzed in the residents of Ganghwa, Cheorwon, Paju, and Goseong from 2017 to 2018. In Ganghwa and Cheorwon, 1.6% and 1.2% of residents, respectively, were PvCSP-antibody-positive in 2018, which indicates a decrease of 0.4% in the positive rate compared to 2017. The annual parasite incidence (API) in Ganghwa and Cheorwon was 24.9 and 10.5 in 2017 and 20.3 and 10.7 in 2018, respectively. Although the changes were not significant, the API in Ganghwa decreased slightly by 4.5 in 2018 compared to the previous year. In Paju and Goseong, 3.9% and 2.0% of residents were positive for the PvCSP antibody. The API in Paju was 13.1 in 2017 and 16.0 in 2018, although no malaria patients were reported for the 2 years. Therefore, the results suggest that PvCSP is a useful antigen for confirming initial malaria infection. Additionally, considering that the antibody is relatively transient, it can be employed for sero-epidemiological studies to determine the extent of malaria transmission in the current year.

• Parasites, Hosts and Diseases
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• v.51 no.5
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• pp.557-562
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• 2013

In contrast to the gradual reduction in the number of locally transmitted malaria cases in China, the number of imported malaria cases has been increasing since 2008. Here, we report a case of a 39-year-old Chinese man who acquired Plasmodium ovale wallikeri infection while staying in Ghana, West Africa for 6 months in 2012. Microscopic examinations of Giemsa-stained thin and thick blood smears indicated Plasmodium vivax infection. However, the results of rapid diagnostic tests, which were conducted 3 times, were not in agreement with P. vivax. To further check the diagnosis, standard PCR analysis of the small-subunit rRNA gene was conducted, based on which a phylogeny tree was constructed. The results of gene sequencing indicated that this malaria is a variant of P. ovale (P. ovale wallikeri). The infection in this patient was not a new infection, but a relapse of the infection from the one that he had contracted in West Africa.