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Malaria continues to be one of the most crucial infectious burdens in endemic areas worldwide, as well as for travelers visiting malaria transmission regions. It has been reported that 8-aminoquinolines are effective against the Plasmodium species, particularly primaquine, for anti-hypnozoite therapy in P. vivax malaria. However, primaquine causes acute hemolytic anemia in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Therefore, G6PD deficiency testing should precede hypnozoite elimination with 8-aminoquinoline. Several point-of-care devices have been developed to detect G6PD deficiency. The aim of the present study was to evaluate the performance of a novel, quantitative G6PD diagnostics based on a metagenomic blue fluorescent protein (mBFP). We comparatively evaluated the sensitivity and specificity of the G6PD diagnostic modality with standard methods using 120 human whole blood samples. The G6PD deficiency was spectrophotometrically confirmed. The performance of the G6PD quantitative test kit was compared with that of a licensed control medical device, the G6PD strip. The G6PD quantitative test kit had a sensitivity of 95% (95% confidence interval (CI): 89.3-100%) and a specificity of 100% (95% CI: 94.3-100%). This study shows that the novel diagnostic G6PD quantitative test kit could be a cost-effective and time-efficient, and universally mandated screening tool for G6PD deficiency.

An understanding of the knowledges, attitudes and perceptions of different populations is key for public health policy makers. Here, a survey was performed on knowledge, attitudes, and perceptions about malaria diagnosis, prevention, control, and treatment. The 407 survey participants included both uninfected inhabitants and patients from 2 cities (Gimpo- and Paju-si) of Northern Gyeonggi-do, known as high-risk areas for vivax malaria. We used community-based study design and non-probability sampling method using the primary data. Association between variables were tested using χ2-tests. In general, the information on malaria reported by the participants in this study was unsystematic and included inaccurate details. The knowledge of malaria symptoms, identified as headache, chills and fever, was high, but the surveyed community lacks knowledge of the specific medications used for malaria treatment, with a large number of respondents having no knowledge of any form of medication. Survey questions with high correct answer rates included questions about easy treatment of malaria in Korea, the high daytime activity of malaria-borne mosquitoes, and the infection risk posed by outdoor activities. However, a large portion of the respondents was unable to provide simple medical and biological information about the disease. This study aimed to comprehensively evaluate the knowledge, attitude, and practical behavior of the surveyed community with respect to malaria and the implications reported here could be applicable to other malaria endemic areas in Korea.

The prevalence and intensity of Opisthorchis viverrini metacercariae (OvMc) were investigated in fish from 3 southern administrative regions along the Mekong River in Cambodia, i.e., Phnom Penh, Takeo, and Kandal Provinces from 2017 to 2020. A total of 295 freshwater fish (24 species) were transported to our laboratory with ice and examined using the artificial digestion method. In Phnom Penh, among 4 fish species positive for OvMc, 9 (23.7%) of 38 specimens examined were infected, and their intensity of infection averaged 4.3 metacercariae per infected fish. In Takeo Province, among 10 fish species positive for OvMc, 24 (38.1%) out of 63 fish examined were infected, and their intensity of infection was av. 14.4 metacercariae per infected fish. In particular, all of 3 Osteochilus schlegelii fish examined were infected, and their infection intensity was high, 34.7 metacercariae per fish. In Kandal Province, among 6 fish species positive for OvMc, 46 (90.2%) out of 51 specimens examined were infected, and their infection intensity was 24.0 metacercaraie per infected fish. All fish of Systomus orphoides (n=17), Barbonymus altus (n=14), and Rasbora aurotaenia (n=2) were infected, and their intensity of infection averaged 37.7, 21.6, and 18.5 metacercariae per fish, respectively. Metacercariae of Haplochis yokogawai, Haplorchis taichui, and Centrocestus formosanus were detected in fish from Takeo and Kandal Provinces. From these results, it has been confirmed that a variety of fish species from Phnom Penh, Takeo, and Kandal Provinces are commonly infected with OvMc, and preventive measures to avoid human O. viverrini infection should be performed in Cambodia.

The endemicity of zoonotic trematode metacercariae (ZTM) was investigated with total 871 freshwater fishes (19 species) from Deokcheon-gang (a branch stream of Gyeongho-gang) in Sancheong-gun, Gyeongsangnam-do, Korea for 3 years (2018-2020). All fishes were examined with the artificial digestion method. The metacercariae of Clonorchis sinensis (CsMc) were detected in 233 (36.3%) out of 642 fish in 11 positive fish species (PFS), and their infection intensity was 27 per fish infected (PFI). Especially, in index fish, Puntungia herzi, of CsMc infection, prevalence was 64.2% and infection intensity was 37 PFI. Metagonimus spp. metacercariae (MsMc) were found in 760 (87.5%) out of 869 fish in 18 PFS and their infection intensity was 228 PFI. In sweet smelt, Plecoglossus altivelis, the prevalence of MsMc was 97.6% and their infection intensity was 3,570 PFI. Centrocestus armatus metacercariae were detected in 209 (29.4%) out of 710 fish in 8 PFS and their infection intensity was 1,361 PFI. Echinostoma spp. metacercariae were found in 293 (42.6%) out of 688 fish in 15 PFS and their infection intensity was 5 PFI. Metacercariae of Clinostomum complanatum and Metorchis orientalis were also detected in 2.7% and 21.2% fish in 4 PFS and their infection intensities were 3.1 and 3.4 PFI respectively. By the present study, it was confirmed that some species of ZTM including CsMc and MsMc are more or less prevalent in fishes from Deokcheon-gang in Sancheong-gun, Gyeongsangnam-do, Korea.

The incidence of vivax malaria in Korea was reduced to a low plateau. For successful elimination of vivax malaria, socio-behavioral changes in the communities are essential. This study aimed to figure out awareness of the inhabitants on the vivax malaria endemicity. The 407 participants including vivax malaria patients and uninfected inhabitants in Gimpo- and Paju-si, Gyeonggi-do, known as high-risk areas in Korea. We used a community-based study design and non-probability sampling method using primary data. Except for the perception about the public health facilities’ capability to cope with anti-malaria programs, the 2 groups of participants shared the same level of awareness about public promotional and educational measures and opinions for malaria elimination from the community. Thus, our future goals for malaria prevention and elimination are to develop more active and well-organized community-based education and evaluation programs collaborating with the community healthcare authorities and local governments.

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.

The infection status of zoonotic trematode metacercariae (ZTM) was investigated in total 568 freshwater fishes (19 species) from the irrigation canal of Togyo-jeosuji (Reservoir) in Cheorwon-gun, Gangwon-do, the Republic of Korea for 3 years (2018-2020). All fishes were examined using the artificial digestion method. The metacercariae of Clonorchis sinensis (CsMc) were detected in 180 (43.8%) out of 411 fish of positive species, and their infection intensity was 38 per fish infected (PFI). Especially, in 2 fish species, i.e., Pseudorasbora parva and Puntungia herzi, the prevalence was 82.1% and 31.3%, and the infection intensity with CsMc was 88 and 290 PFI, respectively. Metagonimus spp. metacercariae (MsMc) were found in 403 (74.1%) out of 544 fish of positive species, and their infection intensity was 62 PFI. In the pale chub, Zacco platypus, the prevalence of MsMc was 98.6%, and their infection intensity was 144 PFI. Centrocestus armatus metacercariae were detected in 171 (38.9%) out of 440 fish of positive species, and their infection intensity was 1,844 PFI. Echinostoma spp. metacercariae were found in 94 (19.6%) out of 479 fish of positive species, and their infection intensity was 3 PFI. Metorchis orientalis metacercariae were detected in 43 (29.3%) out of 147 fish of positive species, and their infection intensity was 4 PFI. By the present study, it has been confirmed that some species of ZTM, including CsMc and MsMc, are prevalent in fishes from the irrigation canal of Togyo-jeosuji in Cheorwon-gun, Gangwon-do, Korea.

The infection status with Clonorchis sinensis metacercariae (CsMc) was examined in freshwater fishes from Yongjeon-cheon (a branch of Nakdong-gang) located in Cheongsong-gun, Gyeongsangbuk-do, the Republic of Korea (Korea). A total of 750 fishes in 19 species were examined by the artificial digestion method for 2 years (2019 and 2020). CsMc were detected in 378 (51.4%) out of 735 fishes in 14 species (73.7%), and the infection intensity was 666 per fish infected. In 2019, CsMc were found in 172 (68.0%) out of 253 fishes in 10 species, and the infection intensity was 565 per fish infected. In 2020, CsMc were detected in 206 (62.2%) out of 331 fishes in 10 species, and the infection intensity was 751 per fish infected. The other zoonotic trematode, ie. Metagonimus spp., Centrocestus armatus, Echinostoma spp. and Clinostomum complanatum, metacercariae were also detected in fishes from the survey streams, but their endemicities were relatively low. Conclusively, it was first confirmed that CsMc are highly endemic in fishes from Yongjeon-cheon in Cheongsong-gun, Gyeongsangbuk-do, Korea.

Heliminthic paramyosin is a multifunctional protein that not only acts as a structural protein in muscle layers but as an immune-modulatory molecule interacting with the host immune system. Previously, we found that paramyosin from Clonorchis sinensis (CsPmy) is bound to human complement C9 protein (C9). To analyze the C9 binding region on CsPmy, overlapping recombinant fragments of CsPmy were produced and their binding activity to human C9 was investigated. The fragmental expression of CsPmy and C9 binding assays revealed that the C9 binding region was located at the C-terminus of CsPmy. Further analysis of the C-terminus of CsPmy to narrow the C9 binding region on CsPmy indicated that the region flanking731Leu–780 Leu was a potent C9 binding region. The CsPmy fragments corresponding to the region effectively inhibited human C9 polymerization. These results provide a precise molecular basis for CsPmy as a potent immunomodulator to evade host immune defenses by inhibiting complement attack.

A survey was performed to investigate the infection status of zoonotic helminth larvae in fish from a local market of North Dagon District in Yangon City, Myanmar. A total of 486 fish in 13 species were collected 8 times from December 2015 to December 2019. All fish were transported under ice to a laboratory in Korea and examined for helminth larvae using artificial digestion method. Larval gnathostomes and metacercariae of more than 8 zoonotic trematode species, i.e., Opisthorchis viverrini, Haplorchis taichui, H. pumilio, H. yokogawai, Centrocestus spp., Stellantchasmus falcatus, Pygidiopsis cambodiensis, and Procerovum sp., were detected. Larval gnathostomes were found in 58 (16.0%) out of 362 fish of 6 species, with mean intensity of 2.8 per fish infected. Metacercariae of O. viverrini were detected in 10 (2.9%) out of 349 fish of 5 species, with mean intensity of 16.9 per fish infected. Metacercarial prevalences of 4 intestinal flukes, H. taichui, H. pumilio, H. yokogawai, and Centrocestus spp., were 16.8%, 26.0%, 12.5%, and 15.0% in the positive fish species, respectively, and mean metacercarial intensity was 63.3, 26.8, 86.2, and 8.7 per fish infected. Metacercariae of S. falcatus and P. cambodiensis were detected only from the mullet, Chelon macrolepis. Metacercariae of Procerovum sp. were found in Channa striata and Anabas testudineus. Collectively, it was confirmed that the fish were infected with gnathostome larvae and metacercariae of O. viverrini and intestinal flukes in Yangon City, Myanmar.

Knockdown resistance (kdr) mutations in the voltage-gated sodium channel (VGSC) of mosquitoes confer resistance to insecticides. Although insecticide resistance has been suspected to be widespread in the natural population of Aedes aegypti in Myanmar, only limited information is currently available. The overall prevalence and distribution of kdr mutations was analyzed in Ae. aegypti from Mandalay areas, Myanmar. Sequence analysis of the VGSC in Ae. aegypti from Myanmar revealed amino acid mutations at 13 and 11 positions in domains II and III of VGSC, respectively. High frequencies of S989P (68.6%), V1016G (73.5%), and F1534C (40.1%) were found in domains II and III. T1520I was also found, but the frequency was low (8.1%). The frequency of S989P/V1016G was high (55.0%), and the frequencies of V1016G/F1534C and S989P/V1016G/F1534C were also high at 30.1% and 23.5%, respectively. Novel mutations in domain II (L963Q, M976I, V977A, M994T, L995F, V996M/A, D998N, V999A, N1013D, and F1020S) and domain III (K1514R, Y1523H, V1529A, F1534L, F1537S, V1546A, F1551S, G1581D, and K1584R) were also identified. These results collectively suggest that high frequencies of kdr mutations were identified in Myanmar Ae. aegypti, indicating a high level of insecticide resistance.

Clonorchis sinensis is a food-borne trematode that infects more than 15 million people. The liver fluke causes clonorchiasis and chronical cholangitis, and promotes cholangiocarcinoma. The underlying molecular pathogenesis occurring in the bile duct by the infection is little known. In this study, transcriptome profile in the bile ducts infected with C. sinensis were analyzed using microarray methods. Differentially expressed genes (DEGs) were 1,563 and 1,457 at 2 and 4 weeks after infection. Majority of the DEGs were temporally dysregulated at 2 weeks, but 519 DEGs showed monotonically changing expression patterns that formed seven distinct expression profiles. Protein-protein interaction (PPI) analysis of the DEG products revealed 5 sub-networks and 10 key hub proteins while weighted co-expression network analysis (WGCNA)-derived gene-gene interaction exhibited 16 co-expression modules and 13 key hub genes. The DEGs were significantly enriched in 16 Kyoto Encyclopedia of Genes and Genomes pathways, which were related to original systems, cellular process, environmental information processing, and human diseases. This study uncovered a global picture of gene expression profiles in the bile ducts infected with C. sinensis, and provided a set of potent predictive biomarkers for early diagnosis of clonorchiasis.

Mosquitoes are globally distributed and important vectors for the transmission of many human diseases. Mosquito control is a difficult task and the cost of preventing mosquito-borne diseases is much lower than that for curing the associated diseases. Thus, chemical control remains the most effective tool for mosquito. Due to the long-term intensive use of insecticides to control mosquito vectors, resistance to most chemical insecticides has been reported. This study aimed to investigate the relationship between insecticide resistance and target site mutation of L1014 kdr and G119 ace alleles in 5 species/species group of mosquitoes (Aedes vexans, Ae. albopictus, Anopheles spp., Culex pipiens complex, and Cx. tritaeniorhynchus) obtained from 6 collection sites. For Anopheles spp., the proportion of mosquitoes with mutated alleles in L1014 was 88.4%, homozygous resistant genotypes were observed in 46.7%, and heterozygous resistant genotypes were observed in 41.8%. For the Cx. pipiens complex and Cx. tritaeniorhynchus species, homozygous resistant genotypes were found in 25.9% and 9.8%, respectively. However, target site mutation of L1014 in the Ae. vexans nipponii and Ae. albopictus species was not observed. Anopheles spp., Cx. pipiens complex, and Cx. tritaeniorhynchus mosquitoes were resistant to deltamethrin and chlorpyriphos, whereas Ae. vexans nipponii and Ae. albopictus were clearly susceptible. We also found a correlation between the resistance phenotype and the presence of the L1014 kdr and G119 ace mutations only in the Anopheles spp. population. In this study, we suggest that insecticide resistance poses a growing threat and resistance management must be integrated into all mosquito control programs.

Chinese edible frogs, Hoplobatrachus rugulosus, were examined to estimate the potential risks of human gnathostomiasis and sparganosis in Myanmar. A total of 20 frogs were purchased in a local market of Yangon and examined with naked eyes and the artificial digestion method after skin peeling in June 2018 and June 2019. Larvae of gnathostomes and Spirometra (=spargana) were detected in 15 (75.0%) and 15 (75.0%) frogs with average intensities of 10.5 and 6.3 larvae per infected frog, respectively. Gnathostome larvae were 2.75-3.80 (av. 3.30) mm long and 0.29-0.36 (0.33) mm wide. They had a characteristic head bulb with 4 rows of hooklets, a muscular long esophagus, and 2 pairs of cervical sac. The mean number of hooklets were 41, 44, 47, and 50 on the 1st, 2nd, 3rd, and 4th row, respectively. Collected spargana were actively moving, particularly with the scolex part, and have ivory-white color and variable in size. Conclusively, it has been first confirmed that Chinese edible frogs, H. rugulosus, are highly infected with larval gnathostomes and spargana in this study. Consuming these frogs is considered a potential risk of human gnathostomiasis and sparganosis in Myanmar.

The infection status of digenetic trematode metacercariae (DTM) was investigated in fishes from coastal lakes in Gangwon-do, the Republic of Korea (Korea). All fishes collected in 5 lakes were examined with the artificial digestion method. More than 10 species, i.e., Metagonimus spp., Pygidiopsis summa, Centrocestus armatus, Metorchis orientalis, M. taiwanensis, Clinostomum complanatum, Echinostoma spp., Stictodora spp., Diplostomum sp. and Diplostomid No. 1. by Morita (1960), of DTM were detected in fishes from 5 coastal lakes in Gangwon-do. Metagonimus spp. metacercariae were found in 52 (41.3%) out of 126 sea rundace, Tribolodon hakonensis, from 5 lakes, and their density was 14.6 per fish infected. P. summa metacercariae were detected in 48 (84.2%) out of 57 mullets from 5 lakes, and their density was 316 per fish infected. C. armatus metacercariae were detected in 7 (14.6%) T. hakonensis and 3 (15.0%) Tridentiger brevispinis from Hyang-ho, and 5 (19.2%) Acanthogobius flavimanus from Gyeongpo-ho. Stictodora spp. metacercariae were found in 4 fish species, i.e., Tridentiger obscurus, Tridentiger trigonocephalus, Chelon haematocheilus, and Acanthogobius lactipes, from Gyeongpo-ho. Total 15 C. complanatum metacercariae were detected in 2 (9.1%) crucian carp, Carassius auratus, from Songji-ho. M. taiwanensis metacercariae were found in T. hakonensis from Hyang-ho and Gyeongpo-ho and in Pseudorasbora parva from Gyeongpo-ho. Total 11 M. orientalis metacercariae were detected in 3 (6.3%) T. hakonensis from Hyang-ho. From the above results, it was confirmed that various species of DTM are infected in fishes from coastal lakes in Gangwon-do, Korea.

Cathepsin D (CatD, EC 3.4.23.5) is a member belonging to the subfamily of aspartic endopeptidases, which are classified into the MEROPS clan AA, family A1. Helminth parasites express a large set of different peptidases that play pivotal roles in parasite biology and pathophysiology. However, CatD is less well known than the other classes of peptidases in terms of biochemical properties and biological functions. In this study, we identified 2 novel CatDs (CsCatD1 and CsCatD2) of Clonorchis sinensis and partially characterized their properties. Both CsCatDs represent typical enzymes sharing amino acid residues and motifs that are tightly conserved in the CatD superfamily of proteins. Both CsCatDs showed similar patterns of expression in different developmental stages of C. sinensis, but CsCatD2 was also expressed in metacercariae. CsCatD2 was mainly expressed in the intestines and eggs of C. sinensis. Sera obtained from rats experimentally infected with C. sinensis reacted with recombinant CsCatD2 beginning 2 weeks after infection and the antibody titers were gradually increased by maturation of the parasite. Structural analysis of CsCatD2 revealed a bilobed enzyme structure consisting of 2 antiparallel β-sheet domains packed against each other forming a homodimeric structure. These results suggested a plausible biological role of CsCatD2 in the nutrition and reproduction of parasite and its potential utility as a serodiagnostic antigen in clonorchiasis.

We are going to describe the female soboliphymid nematodes, which were recovered from the stomach of a Asian badger, Meles leucurus (Mammalia: Mustelidae), in Geochang-gun, Gyeongsangnam-do, Korea. In February 1998, we found 2 peculiar nematodes with a cup-like organ in the anterior end from the stomach of badger. Recovered worms were fixed with 10% formalin, cleared in glycerin-alcohol solution and observed under a light microscope with a micrometer. They were 34.46 (33.43-35.50) mm long by 2.13 mm at maximum width. Cephalic sucker cup-like, 3.34 (3.13-3.55) mm wide, 2.40 (2.25-2.55) mm long, with the oral aperture and meridionally striated on the buccal capsule. Oral aperture 2.38 mm in diameter. Circumoral membrane 0.41 (0.38-0.45) mm wide. Esophagus muscular, 4.81 (4.50-5.00) mm long by 0.80 (0.78-0.83) mm at maximum width. Vulva situated at 3.13 mm ventro-anterior level from the esophago-intestinal junction. Vagina anteriad, 3.38 mm long, making a canal from the uterus to the vulva opening. Uterus single, large. Tail 0.35 (0.33-0.38) mm long. Intrauterine eggs long elliptical, 0.058-0.065 (0.062) mm long and 0.030-0.033 (0.031) mm wide. Based on the some morphological characters and host-specificity, our specimens are nearly identical with S. baturini. Therefore, the present report describes S. baturini for the first time in Korea.

Toxoplasma gondii is an apicomplexan parasite that can cause toxoplasmosis in a wide range of warm-blooded animals including humans. In this study, we analyzed seroprevalence of T. gondii among 467 school children living in the rural areas of Pyin Oo Lwin and Naung Cho, Myanmar. The overall seroprevalence of T. gondii among school children was 23.5%; 22.5% of children were positive for T. gondii IgG, 0.4% of children were positive for T. gondii IgM, and 0.6% of children were positive for both T. gondii IgG and IgM. Geographical factors did not significantly affect the seroprevalence frequency between Pyin Oo Lwin and Naung Cho, Myanmar. No significant difference was found between males (22.2%) and females (25.0%). The overall seroprevalence among school children differed by ages (10 years old [13.6%], 11–12 years old [19.8%], 13–14 years old [24.6%], and 15–16 years old [28.0%]), however, the result was not significant. Polymerase chain reaction analysis for T. gondii B1 gene for IgG-positive and IgM-positive blood samples were negative, indicating no direct evidence of active infection. These results collectively suggest that T. gondii infection among school children in Myanmar was relatively high. Integrated and improved strategies including reinforced education on toxoplasmosis should be implemented to prevent and control T. gondii infection among school children in Myanmar.

The infection status with Clonorchis sinensis metacercariae (CsMc) was examined in freshwater fishes from Yangcheon (a branch of Gyeongho-gang), which is located in Sancheong-gun, Gyeongsangnam-do, the Republic of Korea. Total 2,201 fishes in 26 species were examined by the artificial digestion method through 7 years. CsMc were detected in 1,171 (53.2%) fishes in 21 spp. (80.8%) and their density was 85 per fish infected. Total 532 (99.6%) out of 534 Pungtungia herzi (index fish) examined were infected with 147 CsMc per fish infected. Metacercarial densities in this fish were highest in 2015 (179 CsMc), followed by 2012 (168), 2013 (152), 2016 (145), 2014 (114), and 2017 (89) respectively. In the gobioninid fish group, i.e., P. herzi, Sarcocheilichthys spp., Squalidus spp., Pseudogobio esocinus, Hemibarbus longirostris, and Hemibarbus labeo, 841 (92.7%) fishes were infected with 117 CsMc per fish infected. Total 250 (54.7%) acheilognathinid fish (bitterlings), Acheilognathus spp. and Acanthorhodeus spp. were infected with 5.8 CsMc. In the rasborinid fish (chubs) group, i.e., Zacco platypus, Zacco temminckii, and Zacco koreanus, 77 (13.7%) out of 563 fish examined were infected with 2.4 CsMc in average. The susceptibility indices of CsMc were 49.09 in the overall positive fish group, 104.15 in the gobioninid group, 3.17 in the acheilognathinid group and 0.35 in the rasborinid fish group respectively. Only 1 CsMc was detected in 3 fish species, Coreoperca herzi, Channa argus, and Lepomis macrochirus, respectively. Conclusively, it was confirmed that CsMc are moderately prevalent in fishes from Yangcheon in Sancheon-gun, Gyeongsangnam-do, Korea.

We surveyed on the infection status of zoonotic trematode metacercariae (ZTM) in freshwater fishes from Soyang-cheon (a branch stream of Mangyeong-gang) in Wanju-gun, Jeollabuk-do, the Republic of Korea. A total of 927 fishes were individually examined with the artificial digestion method during 2013-2015 (462 fish in 15 spp.) and 2018-2019 (465 fish in 25 spp.). Clonorchis sinensis metacercariae were detected in 207 (31.4%) out of 659 fishes in 14 positive fish species (PFS), and their mean intensity was 114 per fish infected (PFI). Metagonimus spp. metacercariae were found in 302 (37.4%) out of 808 fishes in 21 PFS, and their mean intensity was 12 PFI. Centrocestus armatus metacercariae were detected in 222 (59.0%) out of 376 fishes in 12 PFS, and their mean intensity was 383 PFI. Echinostoma spp. metacercariae were found in 139 (22.1%) out of 628 fishes in 10 PFS, and their mean intensity was 7 PFI. Clinostomum complanatum metacercariae were detected in 14 (6.5%) out of 214 fishes in 4 PFS, and their mean intensity was 2.4 PFI. Metorchis orientalis metacercariae were detected in 36 (13.5%) out of 267 fishes in 5 PFS, and their mean intensity was 4.3 PFI. Conclusively, the prevalence and infection intensity of ZTM is generally not so high in fishes from Soyang-cheon. However, those of C. sinensis metacercariae are more or less higher in 2 fish species, Pungtungia herzi and Sarcocheilichthys variegatus wakiyae.

The infection status of zoonotic trematode metacercariae (ZTM) was surveyed in freshwater fishes from the water systems of Geum-gang (River) in the Republic of Korea (Korea). A total of 1,161 freshwater fishes from 6 local sites of Geum-gang were examined with the artificial digestion method for 4 years (2012-2015). Clonorchis sinensis metacercariae were detected in 122 (37.2%) out of 328 fishes in the positive fish species from 4 surveyed areas, and their mean intensity was 43 per fish infected. Metagonimus spp. metacercariae were found in 432 (51.7%) out of 835 fishes in the positive fish species from all 6 surveyed areas, and their mean intensity was 30 per fish infected. Centrocestus armatus metacercariae were detected in 285 (75.0%) out of 380 fishes in the positive fish species from 6 surveyed areas, and their mean intensity was 2,100 per fish infected. Echinostoma spp. metacercariae were found in 56 (19.7%) out of 284 fishes in the positive fish species from 5 surveyed areas, and their mean intensity was 10 per fish infected. Clinostomum complanatum metacercariae were detected in 98 (57.3%) out of 171 fishes in the positive fish species from only 2 surveyed areas, and their mean intensity was 11 per fish infected. Conclusively, the endemicity of ZTM is not so high in fishes from water systems of Geum-gang in Korea although it is more or less different by fish species, surveyed areas and ZTM species.

Present study was performed to know the infection status of Gnathostoma sp. larvae in swamp eels from Cambodia. We purchased total 30 Asian swamp eels, Monopterus albus, from local markets in Pursat and Takeo Provinces and Phnom Penh on May and November 2017 and May 2018. All collected eels were transferred to our laboratory with ice and each of them was examined by artificial digestion method. A total of 15 larval gnathostomes (1-5 larvae) were detected from 55.6% (5/9) swamp eels in Pursat Province. No larval gnathostomes were found in 21 swamp eels in Takeo Province and Phnom Penh. The advanced third-stage larvae (AdL3) detected were 2.575-3.825 (3.250) mm in length and 0.375-0.425 (0.386) mm in width. They had the characteristic head bulb (av. 0.104×0.218 mm) with 4 rows of hooklets, long muscular esophagus (1.048 mm), and 2 pairs of cervical sacs (0.615 mm). The number of hooklets in 4 rows on the head bulb was 41, 44, 47, and 50. In scanning electron microscopy, characteristic features were 4 rows of hooklets on the head bulb, cervical papillae, tegumental spines regularly arranged in transverse striations, and anus. The larval gnathostomes were identified as AdL3 of Gnathostoma spinigerum based on the morphological characters. By the present study, it has been confirmed that G. spinigerum larvae are infected in Asian swamp eels, M. albus, in Pursat Province, Cambodia.

Morphological and molecular characterization of clinostomid metacercariae (CMc) was performed with the specimens collected in fish from Korea and Myanmar. Total 6 batches of clinostomid specimens by the fish species and geographical localities, 5 Korean and 1 Myanmar isolates, were analyzed with morphological (light microscopy and SEM) and molecular methods (the cytochrome c oxidase 1 gene and internal transcribed spacer 1/5.8S rRNA sequence). There were some morphological variations among CMc specimens from Korea. However, some morphometrics, i.e., the size of worm body and each organ, ratio of body length to body width, and morphology of cecal lumens, were considerably different between the specimens from Korea and Myanmar. The surface ultrastructures were somewhat different between the specimens from Korea and Myanmar. The CO1 sequences of 5 Korean specimens ranging 728-736 bp showed 99.6-100% identity with Clinostomum complanatum (GenBank no. KM923964). They also showed 99.9-100% identity with C. complanatum (FJ609420) in the ITS1 sequences ranging 692-698 bp. Meanwhile, the ITS1 sequences of Myanmar specimen showed 99.9% identity with Euclinostomum heterostomum (KY312847). Five sequences from Korean specimens clustered with the C. complanatum genes, but not clustered with Myanmar specimens. Conclusively, it was confirmed that CMc from Korea were morphologically and molecularly identical with C. complanatum and those from Myanmar were E. heterostomum.

A small survey was performed to investigate the recent infection status of Clonorchis sinensis and other zoonotic trematode metacercariae in freshwater fish from a local market of Yen Bai city, Yen Bai province, northern Vietnam. A total of 118 fish in 7 species were examined by the artificial digestion method on March 2016. The metacercariae of 4 species of zoonotic trematodes, i.e., C. sinensis, Haplorchis pumilio, Haplorchis taichui, and Centrocestus formosanus, were detected. The metacercariae of C. sinensis were found in 62 (69.7%) out of 89 fish (5 species), and their intensity of infection was very high, 81.2 per fish infected. Prevalences of 3 intestinal flukes, H. pumilio, H. taichui and C. formosanus, were 75.0%, 47.6%, and 31.7% in positive fish species, respectively, with the metacercarial intensities of 15.5, 10.3, and 2.2 per fish infected. From the above results, it has been confirmed that various species of freshwater fish continue to play the role of the infection source of C. sinensis and other zoonotic trematodes in Yen Bai city, Yen Bai province, northern Vietnam. It is of particular note that the prevalence and intensity of C. sinensis metacercariae are much higher than those reported in previous studies in fish in northern Vietnam.

Historically, Plasmodium vivax malaria has been one of the most highly endemic parasitic diseases in the Korean Peninsula. Until the 1970s, vivax malaria was rarely directly lethal and was controlled through the Korean Government Program administered by the National Malaria Eradication Service in association with the World Health Organization's Global Malaria Eradication Program. Vivax malaria has re-emerged in 1993 near the Demilitarized Zone between South and North Korea and has since become an endemic infectious disease that now poses a serious public health threat through local transmission in the Republic of Korea. This review presents major lessons learned from past and current malaria research, including epidemiological and biological characteristics of the re-emergent disease, and considers some interesting patterns of diversity. Among other features, this review highlights temporal changes in the genetic make-up of the parasitic population, patient demographic features, and spatial distribution of cases, which all provide insight into the factors contributing to local transmission. The data indicate that vivax malaria in Korea is not expanding expo- nentially. However, continued surveillance is needed to prevent future resurgence.

Plasmodium vivax is more challenging to control and eliminate than P. falciparum due to its more asymptomatic infections with low parasite densities making diagnosis more difficult, in addition to its unique biological characteristics. The potential re-introduction of incidence cases, either through borders or via human migrations, is another major hurdle to sustained control and elimination. The Republic of Korea has experienced re-emergence of vivax malaria in 1993 but is one of the 32 malaria-eliminating countries to-date. Despite achieving successful nationwide control and elimination of vivax malaria, the evolutionary characteristics of vivax malaria isolates in the Republic of Korea have not been fully understood. In this review, we present an overview of the genetic variability of such isolates to increase understanding of the epidemiology, diversity, and dynamics of vivax populations in the Republic of Korea.

Acanthamoeba spp. are free-living protozoa that are opportunistic pathogens for humans. Cysteine proteases of Acanthamoeba have been partially characterized, but their biochemical and functional properties are not clearly understood yet. In this study, we isolated a gene encoding cysteine protease of A. castellanii (AcCP) and its biochemical and functional properties were analyzed. Sequence analysis of AcCP suggests that this enzyme is a typical cathepsin L family cysteine protease, which shares similar structural characteristics with other cathepsin L-like enzymes. The recombinant AcCP showed enzymatic activity in acidic conditions with an optimum at pH 4.0. The recombinant enzyme effectively hydrolyzed human proteins including hemoglobin, albumin, immunoglobuins A and G, and fibronectin at acidic pH. AcCP mainly localized in lysosomal compartment and its expression was observed in both trophozoites and cysts. AcCP was also identified in cultured medium of A. castellanii. Considering to lysosomal localization, secretion or release by trophozoites and continuous expression in trophozoites and cysts, the enzyme could be a multifunctional enzyme that plays important biological functions for nutrition, development and pathogenicity of A. castellanii. These results also imply that AcCP can be a promising target for development of chemotherapeutic drug for Acanthamoeba infections.

Prompt diagnosis of malaria cases with rapid diagnostic tests (RDTs) has been widely adopted as an effective malaria diagnostic tool in many malaria endemic countries, primarily due to their easy operation, fast result output, and straightforward interpretation. However, there has been controversy about the diagnostic accuracy of RDTs. This study was conducted to evaluate the diagnostic performances of the 2 commercially available malaria RDT kits, RapiGEN Malaria Ag Pf/Pv (pLDH/pLDH) and Asan EasyTestTM Malaria Ag Pf/Pv (HRP-2/pLDH) for their abilities to detect Plasmodium species in blood samples collected from Ugandan patients with malaria. To evaluate the diagnostic performances of these 2 RDT kits, 229 blood samples were tested for malaria infection by microscopic examination and a species-specific nested polymerase chain reaction. The detection sensitivities for P. falciparum of Malaria Ag Pf/Pv (pLDH/pLDH) and Asan EasyTestTM Malaria Ag Pf/Pv (HRP-2/pLDH) were 87.83% and 89.57%, respectively. The specificities of the 2 RDTs were 100% for P. falciparum and mixed P. falciparum/P. vivax infections. These results suggest that the 2 RDT kits showed reasonable levels of diagnostic performances for detection of the malaria parasites from Ugandan patients. However, neither kit could effectively detect P. falciparum infections with low parasitaemia (lt;500 parasites/μl).

To grasp the infection status of Metagonimus spp. metacercariae (MsMc), the freshwater fishes were surveyed from Seomjin-gang (river) and Tamjin-gang in the Republic of Korea. Total 1,604 fishes from 7 local sites of Seomjin-gang and 1,649 fishes from 2 sites of Tamjin-gang were examined for 6 years (2012–2017) by the artificial digestion method. MsMc were detected in fishes from 7 sites, i.e., Osucheon in Imsil-gun (36.3% fish in 6 spp.), Seomjin-gang in Sunchanggun (49.8% in 18 spp.), Songdaecheon in Namwon-si (64.5% in 8 spp.), Seomjin-gang in Gokseong-gun (72.4% in 14 spp.) and in Gurye-gun (78.8% in 17 spp.), Hoengcheon (75.9% in 11 spp.) and Namsancheon (58.9% in 7 spp.) in Hadong-gun. Their average densities were 4.2, 86.8, 39.9, 43.1, 246.5, 173.6 and 67.5 per fish infected respectively. Prevalence with MsMc in rasborinid fish from Seomjin-gang was 89.2% and their intensity was 73.6 per fish infected. Endemicities of MsMc in rasborinid fish from Seomjin-gang were significantly higher in fishes from the lower reaches (prevalence: 98.7%; density: 137) rather than in fishes from the middle (93.5%; 38) and upper (72.4%; 13) reaches. MsMc were also detected in 56.1% and 66.4% fishes from 2 surveyed areas, i.e., the middle reaches in Jangheung-gun and the lower reaches in Gangjin-gun, of Tamjin-gang, and their densities were 147 and 121 per fish infected. In susceptible fishes from Tamjin-gang, the prevalence was 84.1% and density was 227 per fish infected. By the present study, it was confirmed that MsMc is highly prevalent in the fishes from Seomjin-gang and Tamjin-gang in Korea.

This study was conducted to investigate the prevalence of intestinal parasites among students from Goseong-gun, Gangwon-do and Hadong-gun, Gyeongsangnam-do as typical low and high endemic counties. From May to July 2017, a total of 2,033 fecal samples were collected at 27 elementary, 10 junior high, and 8 high schools from 2 counties and examined by the Kato-Katz technique for egg-positive surveys (Collection rate: 37.02% [2,033/5,492]). Of the participants examined, 13 (0.64%) were found to harbor eggs of 3 parasitic species, Trichuris trichiura, Clonorchis sinensis and Metagonimus yokogawai. Based on the regional distribution, the egg-positive rate in Goseong-gun was 0% (0/550) and that in Hadong-gun was 0.88% (13/1,483). The positive rates for C. sinensis, M. yokogawai, and T. trichiura in Hadong-gun were 0.20% (3/1,483), 0.61% (9/1,483), and 0.07% (1/1,483), respectively. The present survey showed that the prevalence of parasitic infection among students is currently very low even in remote, previously endemic areas, and the present status of parasitic diseases can be summarized as some transmission of fish/food-borne trematodes. Thus, it is necessary to carefully, continuously monitor the trematode infection status, particularly of C. sinensis and M. yokogawai.

The present study was performed to investigate the infection status with Clonorchis sinensis metacercariae (CsMc) in fishes from 2 sites, the middle and lower reaches, of Tamjin-gang (River) in Jeollanam-do, the Republic of Korea. Total 1,132 fishes in 22 species were collected from the middle reaches in Jangheung-gun for 4 years (2014-2017) and 517 fishes in 17 species were also collected from the lower reaches in Gangjin-gun in 2014 and 2017. They were all individually examined with the artificial digestion method in our laboratory. CsMc were detected in 322 (28.5%) out of 1,132 fishes from Jangheung-gun, and in 161 (31.1%) out of 517 fishes from Gangjin-gun, and their densities were 51 and 57 per fish infected each. In the fish species with CsMc, positive rates were 61.5% in Jangheung-gun and 62.7% in Gangjin-gun. A total of 222 Pungtungia herzi were examined and they were all infected with CsMc. The average intensity was 103 CsMc in the index fish, P. herzi (95 in Jangheung-gun and 121 in Gangjin-gun). In P. herzi bimonthly examined in 2017, the intensity was commonly most higher in March in 2 surveyed sites, however the significant seasonal endemicity was not showed. Conclusively, it was confirmed that CsMc is more or less prevalent in fishes from Tamjin-gang and their endemicity is higher in fish from the lower reaches in Gangjin-gun than the middle reaches in Jangheung-gun in Jeollanam-do, Korea.

The infection status of Clonorchis sinensis metacercariae (CsMc) was examined in freshwater fish from a highly prevalent site, Wicheon (a branch of Nakdong-gang), which is located in Gunwi-gun, Gyeongsangbuk-do, the Republic of Korea. Total 1,162 fish in 32 species were examined by the artificial digestion method through 6 years. CsMc were detected in 720 (67.5%) out of 1,067 fish (26 spp.) and their density was 610 per fish infected. In the susceptible gobioninid fish group, i.e., Pungtungia herzi, Squalidus gracilis majimae, Squalidus japonicus coreanus, Sarcocheilichthys variegatus wakiyae and Pseudorasbora parva, all of 323 fish were infected with an average of 1,310 CsMc. Total 23 (95.8%) gobioninid fish, i.e., Pseudogobio esocinus, Abbottina springeri, Hemibarbus longirostris, Microphysogobio koreensis, and Microphysogobio jeoni, were infected with 127 CsMc in average. In the acheilognathinid fish (bitterlings) group, the prevalence was 77.0%, and the density was 50 CsMc per fish infected. In the rasborinid fish (chubs) group, i.e., Zacco platypus, Zacco temminckii, Zacco koreanus, and Opsariichthys uncirostris amurensis, 147 (36.5%) out of 403 fish examined were infected with 15 CsMc in average. The susceptibility indices of CsMc were 412 in the overall positive fish group, 1,310 in the gobioninid group-1, 122 in the gobioninid group-2, 38.5 in the acheilognathinid group, and 5.5 in the rasborinid fish group. Conclusively, it was confirmed that CsMc are highly prevalent in fish from Wicheon, and their infection tendency varied according to the subfamily groups in Cyprinidae fish hosts.

A survey was performed to investigate the infection status of zoonotic trematode (ZT) metacercariae in fish from a local market in Yangon City, Myanmar. A total of 264 fish (12 species) were collected through 4 times from December 2013 to June 2015. All collected fish were transferred to our laboratory on ice and examined by the artificial digestion method. More than 7 species of ZT metacercariae, i.e., Haplorchis taichui, H. pumilio, H. yokogawai, Centrocestus spp., Stellantchasmus falcatus, Pygidiopsis cambodiensis, and Procerovum sp. were detected. Metacercariae of H. taichui were collected in 58 (42.3%) out of 137 fish (5 species), and their average density was 42.9 per fish infected. Metacercariae of H. pumilio were detected in 96 (49.0%) out of 196 fish (9 species), and their average density was 23.6 per fish infected. H. yokogawai metacercariae were found in 40 (50.0%) out of 80 fish (5 species), and Centrocestus spp. metacercariae in 91 (50.8%) out of 179 fish (8 species), and their densities were 306 and 25.8 per fish infected, respectively. Metacercariae of S. falcatus and P. cambodiensis were detected only in mullets, Chelon macrolepis. A total of 280 Procerovum sp. metacercariae were found in 6 out of 12 climbing perch, Anabas testudineus. Morphological characteristics of adult flukes recovered from experimental animals were described. It has been first confirmed that fish from Yangon, Myanmar are commonly infected with various species of ZT metacercariae.

A survey was performed to know the infection status of echinostome metacercariae in Cipangopaludina chinensis malleata snails from Korea. Total 75 snails collected in 5 localities, i.e., Imsil-gun, Jeollabuk-do, Hwasun-gun and Shinan-gun (Aphae and Jido), Jeollanam-do, and Jinju-si, Gyeongsangnam-do, were examined for metacercariae by the artificial digestion method. Infection rates of metacercariae were 80.0%, 66.7%, 100%, 60.0%, and 73.3%, and their densities were 39, 32, 183, 19, and 30 per snail infected, respectively. The metacercariae were round, 105-118×105-118 μm in size, with a thin cyst wall, collar spines on the head collar, and excretory granules in 2 canals of excretory tube. Adult flukes were elongated, ventrally curved, and 5,167×939 μm in average size. Head collar distinct, bearing 45 collar spines with 5 end groups on each side. Oral sucker subterminal, pharynx well developed, and esophagus somewhat short. Cirrus sac well developed, with a saccular seminal vesicle, and ventral sucker very large. Ovary elliptical and on the median line of the body. Testes tandem and slightly lobed. Eggs operculated, elliptical, and 90-103×55-60 μm in size. By scanning electron microscopy, the head collar was prominent with 45 collar spines resembling horns of younger stags. Scale-like tegumental spines were densely distributed on the body surface between the head collar and ventral sucker. Conclusively, it has been first confirmed that the life cycle of E. macrorchis is indigenously maintained in Korea, and C. chinensis malleata snails are popularly infected with the metacercariae of this echinostome.

A survey was performed to know the recent infection status of digenetic trematode metacercariae in clams and oysters from 4 sites in western coastal regions of the Republic of Korea (=Korea). Four species of clams (Mactra veneriformis, Ruditapes philippinarum, Cyclina sinensis, and Saxidomus purpuratus) were collected from Taean-gun, Chungcheongnam-do (Province), Buan-gun (County) and Gochang-gun, Jeollabuk-do, and oysters, Crassostrea gigas, from Shinan-gun, Jeollanam-do were transferred to our laboratory on ice and examined by the artificial digestion method. The metacercariae of Himasthla alincia were detected in 3 species of clams, M. veneriformis, R. philippinarum, and C. sinensis from the 3 surveyed areas. The positive rate and the mean density per clam infected were 98.9% (30.8 metacercariae) in M. veneriformis, 60.0% (5.0) in R. philippinarum, and 96.0% (28.4) in C. sinensis. The positive rate (mean density) of Acanthoparyphium tyosenense metacercariae in M. veneriformis was 50.0% (2.1) from Taean-gun and 70.0% (2.8) from Gochang-gun. The metacercariae of Parvatrema spp. were detected in M. veneriformis and R. philippinarum from Taean-gun and Gochang-gun; the positive rate (mean density) was 63.3% (4,123) and 50.0% (19) in M. veneriformis, and 6.7% (126) and 100% (238) in R. philippinarum from the 2 regions, respectively. The metacercariae of Gymnophalloides seoi were detected in all 30 oysters from Shinan-gun, and their average density per oyster was 646. From the above results, it has been confirmed that more than 3 species of metacercariae are prevalent in clams from the western coastal regions, and G. seoi metacercariae are still prevalent in oysters from Shinan-gun, Jeollanam-do, Korea.

The present study was performed to record new definitive hosts of Isthmiophora hortensis, and to describe morphological characteristics derived from a variety of worm samples for clarification of its taxonomic validity. Morphological characteristics with dimensions were observed in worm samples (n=21) from naturally infected wild animals, including a raccoon dog Nyctereutes procyonoides from Gimhae-si (City), Gyeongsangnam-do, stray cats and a striped field mouse from several localities, and a wild boar Sus scrofa, from Gurye-gun (County), Jeollanam-do. In addition, adult flukes (n=45) recovered in albino rats experimentally infected with the metacercariae from a freshwater fish species were also subjected to morphological studies. The mean ratios of the body length (BL) to body width (BW) were 5.86 and 5.76 in worms from wild animals and experimental rats, respectively. Those of the ventral sucker to oral sucker were 2.92 and 3.01 in worms from 2 groups. The mean percentages of the hindbody length (HBL) to BL were 42.1 and 41.2 in 2 groups. Those of uterine fields to BL were 9.8 and 12.2 in the 2 worm groups. By the present study, the 2 species of wild animals, the raccoon dog and wild boar, have been added as new definitive hosts for I. hortensis. The morphological characteristics of adult flukes derived from a variety of host source were redescribed to support the taxonomic validity of this echinostome species.

The prevalence of Clonorchis sinensis metacercariae (CsMc) was examined in freshwater fish from the water systems of Seomjin-gang (River), the Republic of Korea. Total 1,604 fish from 7 local sites of Seomjin-gang were examined by artificial digestion methods. The metacercariae of C. sinensis were detected in 102 (39.8%) out of 256 fish (14 species) from the upper reaches of Seomjin-gang, i.e., Osucheon (22.3% in 6 fish species) in Imsil-gun, and Seomjin-gang (63.9% in 9 fish species) in Sunchang-gun, Jeollabuk-do. Their average density was 9.0 per infected fish. They were also found in 132 (48.0%) out of 275 fish (12 spp.) from the middle reaches of Seomjin-gang, i.e., Songdaecheon (58.9% in 4 fish species) in Namwon-si, Jeollabuk-do, and Seomjin-gang (45.2% in 10 fish species) in Gokseong-gun, Jeollanam-do. Their average density was 21.0 per infected fish. CsMc were detected in 77 (56.6%) out of 136 fish (11 species) from the lower reaches of Seomjin-gang, i.e., Seomjin-gang (73.3% in 11 fish species) in Gurye-gun, Jeollanam-do, and Namsancheon (8.6% in 1 fish species) in Hadong-gun, Gyeongsangnam-do. Their average density was 64.9 per infected fish. The metacercariae of Metorchis orientalis were also detected in 6 fish species from 4 sites of Seomjin-gang. Conclusively, it has been confirmed that CsMc are more or less prevalent in fish from some water systems of Seomjin-gang in Korea.

Vivax malaria reemerged in Korea in 1993 and the outbreak has been continued with fluctuating numbers of annual indigenous cases. Understanding the nature of the genetic population of Plasmodium vivax circulating in Korea is beneficial for the knowledge of the nationwide parasite heterogeneity and in the implementation of malaria control programs in the country. Previously, we analyzed polymorphic nature of merozoite surface protein-1 (MSP-1) and MSP-3α in Korean P. vivax population and identified the Korean P. vivax population has been diversifying rapidly, with the appearance of parasites with new genetic subtypes, despite the recent reduction of the disease incidence. In the present study, we developed simple PCR-RFLP methods for rapid subtyping of MSP-1 and MSP-3α of Korean P. vivax isolates. These PCR-RFLP methods were able to easily distinguish each subtype of Korean P. vivax MSP-1 and MSP-3α with high accuracy. The PCR-RFLP subtyping methods developed here would be easily applied to massive epidemiological studies for molecular surveillance to understand genetic population of P. vivax and to supervise the genetic variation of the parasite circulating in Korea.

We identified the echinostome metacercariae in Chinese mystery snails, Cipangopaludina chinensis malleata, from Xiengkhuang Province, Lao PDR with morphologies of adult worms recovered. Total 20 snails were examined with artificial digestion method and then the collected metacercariae were orally infected to a mouse and a rat. Adult worms recovered from experimental animals were observed with a light microscope and a SEM. The metacercariae were round, 125×123 µm in average size, with a moderately thick cyst wall, collar spines distributed in the head collar and excretory granules in 2 canals of excretory tube. Adult flukes (3-week-old in a rat) were elongated, ventrally curved and 5.310×1.023 mm in average size. Head collar distinct, bearing 43 collar spines with 5 end group ones on each side. Oral sucker subterminal, prepharynx very short, pharynx well developed, and esophagus relatively short. Cirrus sac well developed, with a saccular seminal vesicle, and ventral sucker very large. Ovary round and on the median line of the body. Testes tandom and elongated. Eggs operculated, elliptical and 90×57 µm in average size. In the SEM observation, the head crown prominent, with 43 collar spines resembled with horns of younger stag. Scale-like tegumental spines were densely distributed on the surface between the head collar and ventral sucker, and their densities were decreased posteriorly. Conclusively, the metacercariae detected in C. chinensis malleata from Lao PDR were identified as those of Echinostoma macrorchis based on the morphological characteristics of adult worms.

The infection status of Clinostomum complanatum metacercariae (CcMc) was broadly surveyed in fishes from water systems of Nakdong-gang (River) in the Republic of Korea (Korea) for 5 years. All 4,468 fishes collected were individually examined by the artificial digestion methods. No CcMc were detected in fishes from Naeseongcheon in Yecheon-gun, Gigyecheon in Gyeongju-si, Gyeongsangbuk-do, and Hamancheon in Haman-gun, Gyeongsangnam-do. In fishes from Wicheon in Gunwi-gun, Gyeongsangbuk-do, CcMc were detected in 180 (15.4%) out of 1,168 fishes and their intensity was 5.8 per fish infected. The prevalences with CcMc in positive fish species from 3 other surveyed areas, i.e., Banbyeoncheon in Yeongyang-gun, Nakdong-gang in Sangju-si and Hoecheon in Goryeong-gun, in Gyeongsangbuk-do were 19.3%, 33.3%, and 19.0% and their intensities were 1.5, 17.6, and 2.6 per fish infected respectively. In fishes from Yangcheon in Sancheong-gun, Gyeongsangnam-do, CcMc were detected in 811 (45.6%) out of 1,779 fishes examined and their intensity was 9.8 per fish infected. The prevalence was most high in Squalidus spp. (97.7%) and followed by acheilognathinid fish (66.8%), Pungtungia herzi (52.0%), rasborinid fish (39.6%) and Hemibarbus spp. (25.9%) from Yangcheon. The intensity was also most high in Squalidus spp. (27.0). The endemicity with CcMc was very low in fishes from water systems of Nakdong-gang in the east coast of Korea. Conclusively, it is confirmed that various fish species act as the second intermediate hosts of C. complanatum, and the endemicities of CcMc are more or less different by the fish species and group from Yangcheon, in Sancheong-gun, Gyeongsangnam-do, Korea.

The infection status of digenetic trematode metacercariae (DTM) was investigated in fishes from 2 representative visiting sites of migratory birds in Gyeongsangnam-do, the Republic of Korea (Korea). A totaly 220 freshwater fishes (7 species) were collected from Junam-jeosuji (reservoir), and 127 fishes (7 species) were also collected from Woopo-neup (swamp) in June and October 2017. As the control group, total 312 fish (22 spp.) from Yangcheon in Sancheong-gun, Gyeongsangnam-do were also collected in June and October 2017. All fishes collected in 3 sites were examined with the artificial digestion method. In the fishes from Junam-jeosuji, more than 4 species, i.e., Clonorchis sinensis, Echinostoma spp., Diplostomum spp. and Cyathocotyle orientalis, of DTM were detected and their endemicy was very low, 0.70. More than 6 species, i.e., C. sinensis, Echinostoma spp., Metorchis orientalis, Clinostomum complanatum, Diplostomum spp. and C. orientalis, of DTM were found in the fishes from Woopo-neup, and their endemicy was low, 5.16. In the fishes from Yangcheon, more than 8 species, i.e., C. sinensis, Metagonimus spp., Centrocestus armatus, C. complanatum, C. orientalis, M. orientalis, Echinostoma spp., and Diplostomum spp., of DTM were detected, and their endemicity was relatively high, 95.48. The percentages of avian trematode metacercariae (ATM) were 99.6% and 94.7% in fishes from Junam-jeosuji and Woopo-neup whereas it was 74.1% in the control site, Yangcheon. The above findings suggested that migratory birds partly affect in endemicity of DTM in the fish in the 2 visiting sites in Gyeongsangnam-do, Korea.

To know the infection status of zoonotic trematode metacercariae in brackish water fish, we surveyed mullets collected from 18 coastal areas in the Republic of Korea. The metacercariae of Pygidiopsis summa were detected in 236 (68.2%) out of 346 mullets examined. They were found in mullets from 15 areas except for those from Boseong-gun (Jeollanam-do), Pohang-si, and Uljin-gun (Gyeongsangbuk-do). Especially in mullets from Taean-gun (Chungcheongnam-do) and Geoje-si (Gyeongsangnam-do), their prevalences were 100% and 95.5%, and the average metacercarial density was more than 1,000 per fish. They were also detected in mullets from 3 coastal lakes, Gyeongpoho, Songjiho, and Hwajinpoho, in Gangwon-do, and their average densities were 419, 147, and 672 per infected fish, respectively. The metacercariae of 5 other heterophyid species, including Heterophyes nocens, Heterophyopsis continua, Metagonimus sp., Stictodora fuscata, and Stictodora lari, were found in the mullets examined. The metacercariae of H. nocens were detected in 66.7, 100, 28.6, 81.6, 3.9, 61.5, and 27.3% of mullets from Muan-gun, Shinan-gun, Haenam-gun, Gangjin-gun, and Boseong-gun (Jeollanam-do), Hadong-gun, and Geoje-si (Gyeongsangnam-do), and their metacercarial intensities were 64, 84, 119, 99, 1, 24, and 24 per fish infected, respectively. From the above results, it has been confirmed that P. summa metacercariae are heavily infected in mullets from coastal areas of Korea. It is suggested that residents who frequently consume raw mullet dish can be easily infected with heterophyid flukes.

We describe here the mass death of predatory carp, Chanodichthys erythropterus, in Korea induced by plerocercoid larvae of Ligula intestinalis as a result of host manipulation. The carcasses of fish with ligulid larvae were first found in the river-edge areas of Chilgok-bo in Nakdong-gang (River), Korea at early February 2016. This ecological phenomena also occurred in the adjacent areas of 3 dams of Nakdong-gang, i.e., Gangjeong-bo, Dalseong-bo, and Hapcheon-Changnyeong-bo. Total 1,173 fish carcasses were collected from the 4 regions. To examine the cause of death, we captured 10 wondering carp in the river-edge areas of Hapcheon-Changnyeong-bo with a landing net. They were 24.0-28.5 cm in length and 147-257 g in weight, and had 2-11 plerocercoid larvae in the abdominal cavity. Their digestive organs were slender and empty, and reproductive organs were not observed at all. The plerocercoid larvae occupied almost all spaces of the abdominal cavity under the air bladders. The proportion of larvae per fish was 14.6-32.1% of body weight. The larvae were ivory-white, 21.5-63.0 cm long, and 6.0-13.8 g in weight. We suggest that the preference for the river-edge in infected fish during winter is a modified behavioral response by host manipulation of the tapeworm larvae. The life cycle of this tapeworm seems to be successfully continued as the infected fish can be easily eaten by avian definitive hosts.

Present study was performed to survey on infection status of Isthmiophora hortensis (formerly Echinostoma hortense) metacercariae (IhMc) in dark sleepers, Odontobutis spp., from some water systems of the Republic of Korea. A total of 237 Odontobutis spp. was collected in the water systems of 5 rivers, i.e., Mangyeong-gang (gang means river), Geum-gang, Tamjin-gang, Seomjin-gang, and Nakdong-gang. They were all examined with artificial digestion method for 5 years (2013-2017). A total of 137 (57.8%) Odontobutis spp. were infected with 14.8 IhMc in average. The prevalence was the highest in Nakdong-gang areas (62.9%) and followed by in Mangyeong-gang (57.1%), Geum-gang (56.3%), Tamjin-gang (54.8%), and Seomjin-gang (53.9%) areas. Metacercarial densities were 28.1 (Geum-gang), 13.9 (Mangyeong-gang), 13.3 (Nakdong-gang), 13.1 (Tamjin-gang), and 2.3 (Seomjin-gang) per infected fish. Especially, in case of Yugucheon (cheon means stream), a branch of Geum-gang, IhMc were detected in all fish (100%) examined and their density was about 48 per fish. By the present study, it was confirmed that the infection status of IhMc is more or less different by the surveyed areas and the dark sleepers, Odontobutis spp., are suitable fish hosts of I. hortensis.

To investigate the infection status of zoonotic trematode metacercariae in yellowfin goby, Acanthogobius flavimanus, from coastal areas of the Republic of Korea (Korea), we examined total 344 gobies from 21 localities with an artificial digestion method from 2013 to 2017. The metacercariae of Stictodora lari were most frequently detected in 45.3% goby from 7 localities, i.e., Taean-gun (Chungcheongnam-do), Gochang-gun (Jeollabuk-do), Muan-gun, Shinan-gun, Haenam-gun (Jeollanam-do), Hadong-gun and Goseong-gun (Gyeongsangnam-do). Their infection rates were 90.0%, 66.7%, 46.7%, 8.0%, 3.3%, 26.7%, and 86.7% and intensities were 1,090, 6.2, 1.6 1.0, 2.0, 2.0, and 7.2 metacercariae per fish infected respectively. Heterophyopsis continua metacercariae were found in 38.2% goby from 6 localities, i.e., Gochang-gun, Muan-gun, Shinan-gun, Gangjin-gun, Boseong-gun (Jeollanam-do) and Goseong-gun, and their intensities were relatively low, 1-21 metacercariae. Stictodora fuscata metacercariae were detected in 61.3% goby from 4 localities, i.e., Taean-gun, Gochang-gun, Hadong-gun and Goseong-gun. Their infection rates were 90.0%, 53.3%, 5.9%, and 73.3% and intensities were 1,081, 3.1, 3.0, and 10.2 metacercariae per fish infected respectively. Heterophyes nocens metacercariae were found in 55.0% goby from Muan-gun and Shinan-gun. Total 3 metacercariae of Isthmiophora hortensis were detected in 2 (8.0%) gobies from Shinan-gun. Total 15 metacercariae of Centrocestus armatus were detected in 5 gobies (33.3%) from Gyeongpo-ho (ho means lake) in Gangneung-si, Gangwon-do. The present study suggests that yellowfin goby, A. flavimanus, acts as the infection sources of zoonotic intestinal flukes in western and southern coastal areas than in eastern coastal areas of Korea.

The present study was performed to determine the infection status of swamp eels with Gnathostoma sp. larvae in Myanmar. We purchased total 37 Asian swamp eels, Monopterus albus, from a local market in Yangon in June and December 2013 and 2014. All collected eels were transferred with ice to our laboratory and each of them was examined by the artificial digestion technique. A total of 401 larval gnathostomes (1-96 larvae/eel) were detected in 33 (89.2%) swamp eels. Most of the larvae (n=383; 95.5%) were found in the muscle. The remaining 18 larvae were detected in the viscera. The advanced third-stage larvae (AdL3) were 2.3-4.4 mm long and 0.25-0.425 mm wide. The characteristic head bulb (0.093 × 0.221 mm in average size) with 4 rows of hooklets, muscular long esophagus (1.025 mm), and 2 pairs of cervical sacs (0.574 mm) were observed by light microscopy. The average number of hooklets in the 1st, 2nd, 3rd, and 4th rows was 41, 45, 48, and 51, respectively. As scanning electron microscopic findings, the characteristic 4-5 rows of hooklets on the head bulb, a cervical papilla, tegumental spines regularly arranged in the transverse striations, and an anus were well observed. Based on these morphological characters, they were identified as the AdL3 of Gnathostoma spinigerum. By the present study, it has been confirmed for the first time that Asian swamp eels, M. albus, from Yangon, Myanmar are heavily infected with G. spinigerum larvae.

The present study was performed to report 15 anisakiasis cases in Korea and to review the Korean cases reported in the literature. Total 32 Anisakis type I larvae were detected in the stomach of 15 patients by the endoscopy. Single worm was detected from 12 cases, and even 9 larvae were found from 2 cases. Epigastric pain was most commonly manifested in almost all cases, and hemoptysis and hematemesis were seen in 1 case each. Symptom manifestations began at 10-12 hr after eating fish in 73.3% cases. Endoscopy was performed 1-2 days after the symptom onset in most cases. The common conger, Conger myriaster, was the probable infection source in 7 cases. In the review of Korean anisakiasis cases, thus far, total 645 cases have been reported in 64 articles. Anisakis type I larva was the most frequently detected (81.3%). The favorable infection site of larvae was the stomach (82.4%). The common conger was the most probable source of human infections (38.6%). Among the total 404 cases which revealed the age and sex of patients, 185 (45.8%) were males, and the remaining 219 (54.2%) were female patients. The age prevalence was the highest in forties (34.7%). The seasonal prevalence was highest in winter (38.8%). By the present study, 15 cases of gastric anisakiasis are added as Korean cases, and some epidemiological characteristics of Korean anisakiasis were clarified.

The infection status of freshwater fish with digenetic trematode metacercariae was examined in water systems of Hantangang and Imjingang (River), the Republic of Korea. A total of 877 (594 from Hantangang and 283 from Imjingang) fishes were examined by the artificial digestion methods. Clonorchis sinensis metacercariae were detected in 7 (1.2%) fishes (in 3 spp.) from Hantangang in Cheorwon-gun, Gangwon-do, and 40 (14.1%) fishes (in 7 spp.) from Munsancheon in Paju-si, Gyeonggi-do. The average densities were 1.9 and 35.6 per fish infected, respectively. Metagonimus spp. metacercariae were detected in 312 (52.5%) and 113 (39.9%) fishes from Hantangang and Imjingang, and their average densities were 47.5 and 9.6 per fish infected, respectively. Centrocestus armatus metacercariae were found in 161 (27.1%) and 70 (24.7%) fishes from Hantangang and Imjingang, and their average number per fish infected was 694 and 82, respectively. Echinostoma spp. metacercariae were detected in 50 (8.4%) and 94 (33.2%) fishes from Hantangang and Imjingang, and their average densities were 9.6 and 23.1 per fish infected, respectively. The infection status of fishes with metacercariae of Stephanoprora spp., Diplostomum spp., Clinostomum complanatum, Metorchis orientalis, and Metorchis taiwanensis were analyzed by surveyed regions. Conclusively, it was confirmed that C. sinensis metacercariae were quite commonly detected in fishes from Munsancheon but rarely from other localities, whereas the metacercariae of other digenetic trematodes were relatively prevalent in fishes from water systems of Hantangang and Imjingang in Korea.

The present study was performed to survey the infection status of zoonotic intestinal trematode (ZIT) in stray cats from 5 major riverside areas in the Republic of Korea. Total 400 stray cats were captured with live-traps in riverside areas of Seomjingang (‘gang’ means river) (203 cats) from June to October 2010, and of Yeongsangang (41), Nakdonggang (57), Geumgang (38), and Hangang (61 cats) from June to October 2011, respectively. Small intestines resected from cats were opened with a pair of scissors in a beaker with 0.85% saline and examined with naked eyes and under a stereomicroscope. More than 16 ZIT species were detected in 188 (92.6%) cats from Seomjingang areas, and the number of worms recovered was 111 per cat infected. In cats from riverside areas of Yeongsangang, Nakdonggang, Geumgang, and Hangang, more than 9, 8, 3, and 5 ZIT species were recovered, and the worm burdens were 13, 42, 11, and 56 specimens per infected cat, respectively. As the members of family Heterophyidae, more than 10 species, i.e., Metagonimus spp., Pygidiopsis summa, Heterophyes nocens, Stellantchasmus falcatus, Heterophyopsis continua, Acanthotrema felis, Centrocestus armatus, Procerovum varium, Cryptocotyle concava, and Stictodora lari, were recovered. More than 5 species of echinostomes, i.e., Echinostoma hortense, Echinochasmus japonicus, Echinochasmus sp., Echinoparyphium sp., and unidentified larval echinostomes, were collected. Plagiorchis spp. were detected in cats from areas of Seomjin-gang and Yeongsangang. From the above results, it has been confirmed that stray cats in 5 major riverside areas of Korea are highly infected with various species of ZITs.

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.