• Parasites, Hosts and Diseases
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• v.44 no.3
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• pp.187-196
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• 2006

The mammalian trematode Paragonimus westermani is a typical digenetic parasite, which can cause paragonimiasis in humans. Host tissues and blood cells are important sources of nutrients for development, growth and reproduction of P. westermani. In this study, a cDNA clone encoding a 47 kDa hemoglobinase of P. westermani was characterized by sequencing analysis, and its localization was investigated immunohistochemically. The phylogenetic tree prepared based on the hemoglobinase gene showed high homology with hemoglobinases of Fasciola hepatica and Schistosoma spp. Moreover, recombinant P. westermani hemoglobinase degradaded human hemoglobin at acidic pH (from 3.0 to 5.5) and its activity was almost completely inhibited by E-64, a cysteine proteinase inhibitor. Immunohistochemical studies showed that P. westermani hemoglobinase was localized in the epithelium of the adult worm intestine implying that the protein has a specific function. These observations suggest that hemoglobinase may act as a digestive enzyme for acquisition of nutrients from host hemoglobin. Further investigations may provide insights into hemoglobin catabolism in P. westermani.

• Parasites, Hosts and Diseases
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• v.41 no.1
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• pp.47-55
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• 2003

We compared patterns of intraspecific polymorphism of two markers with contrasting modes of evolution, nuclear ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA), in the lung fluke, diploid and triploid Paragonimus westermani from three geographical regions of Korea. The genetic distances between three populations of Korean diploid and triploid P. westermani showed no significant difference in the nucleotide sequences of the mitochondrial cytochrome c oxidase subunit 1 (mtCOI) and ribosomaal second internal transcribed spacer (ITS2) genes. A highly resolved strict-consensus tree was obtained that illustrated phylogenetically useful information of the ITS2 and mtCOI sequences from diploid and triploid P. westermani.

• Parasites, Hosts and Diseases
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• v.37 no.1
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• pp.55-57
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• 1999

During the period from October 1996 to November 1998, the infection status of Paragonimus westermani metacercariae in freshwater crayfish (Cambaroides similis) collected from Bogildo (islet), Wando-gun, Chollanam-do, which is known for an endemic area of P. westermani in Korea, were examined. The average infection rate of Paragonimus metacercariae in crayfish was 88.6%, and mean number of metacercariae per infected crayfish was 30.2. This metacercarial density was the highest in the group of weight in 7.1-9.0 g. These results suggest that the natural life cycle of P. westermani is still well-preserved in Bogildo.

• Parasites, Hosts and Diseases
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• v.51 no.6
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• pp.621-627
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• 2013

Paragonimiasis is a food-borne parasitic zoonosis caused by infection with lung flukes of the genus Paragonimus. In Vietnam, research on Paragonimus and paragonimiasis has been conducted in northern and central regions of the country. Using a combination of morphological and molecular methods, 7 Paragonimus species, namely P. heterotremus, P. westermani, P. skrjabini, P. vietnamensis, P. proliferus, P. bangkokenis, and P. harinasutai, have been identified in Vietnam. Of these, the first 3, P. heterotremus, P. westermani, and P. skrjabini, are known to infect humans in other countries. However, in Vietnam, only P. heterotremus, found in some northern provinces, has been shown to infect humans. Even nowadays, local people in some northern provinces, such as Lai Chau and Yen Bai, are still suffering from P. heterotremus infection. In some provinces of central Vietnam, the prevalence and infection intensity of P. westermani metacercariae in freshwater crabs (the second intermediate hosts) are extremely high, but human cases have not been reported. Likewise, although P. skrjabini was found in Thanh Hoa Province, its pathogenicity to humans in Vietnam still remains uncertain. The results of molecular phylogenetic analyses of Vietnamese Paragonimus species provides new insights on the phylogeny and taxonomy of the genus Paragonimus. Comprehensive molecular epidemiological and geobiological studies on the genus in Vietnam and adjacent countries are needed to clarify the biodiversity and public health significance of the lung flukes.

• Parasites, Hosts and Diseases
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• v.30 no.1
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• pp.43-48
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• 1992

Paragonimus westermani is a common fluke in Uorea. The present study aimed to observe the cell mediated immune response in experimental paragonimiasis of mice. The mouse (BALB/c) was orally inoculated with 40 metacercariae of P. westermani from Cambaroides similis. During the infection (1, 2, 4, 6 weeks) of mouse, blastogenic response of splenic Iymphocytes to P. westermani adult antigen, metacercaria antigen, and PHA were observed. Sera from infected and noninfected mice added to normal mouse splenic Lymphocytes with or without PHA. The blastogenic response of splenic Lymphocytes to PHA was reduced after 1 week of infection. However after 6 weeks of infection, the response was restored to the control level. The blastogenic response of splenic Iymphocytes to P. westermani adult or metacercaria antigen increased significantly on 1 week after infection, and maintained up to 6 weeks after infection. The response of non-infected mice was suppressed by addition of the infected mouse serum. The present results suggested that cellular immunity was involved in P. westermani infected mice and that P. westermani anti.serum inhibited proliferation of T Iymphocytes.

• Parasites, Hosts and Diseases
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• v.37 no.4
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• pp.285-287
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• 1999

Changes in the expression level of splenocyte $IFN-{\gamma}$mRNA of Sprague-Dawley (SD) rats infected with Paragonimus westermani were analyzed by competitive reverse transcription-polymerase chain reaction (RT-PCR) followed by southern blot. The template RNA was extracted from the splenocytes of rats infected with 20 metacercariae of P. westermani. The products of competitive RT-PCR were subjected to southern blot and enhanced chemiluminescence (ECL), and analyzed with a densitometer. In comparison with that of uninfected control rat splenocytes (value of 1), the levels of mRNA expression of $IFN-{\gamma}$had changed to 0.747 at 1 week post infection (PI), 0.00175 at 2 week PI, 0.0217 at 3 week PI, 0.194 at 4 week PI and then to 0.537 at 5 week PI. The level at 7 week PI had returned to 1.25, comparable with that of uninfected rats. These results show that, when infected with p. westermani, the levels of $IFN-{\gamma}$ mRNA of SD rat splenocytes were remarkably reduced by more than 500 times at 2 week PI and restored to normal level at 7 week PI.

• Parasites, Hosts and Diseases
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• v.47 no.4
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• pp.425-426
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• 2009

The present study investigated the infection status of Paragonimus westermani metacercariae in freshwater crabs (n = 363) and crayfish (n = 31) from October 2007 to October 2008 using the crush method. All of the freshwater crabs, Eriocheir japonicus, were negative for P. westermani metacercariae while 10 (32.3%) of the 31 examined crayfish were positive. The 10 positive crayfish were caught in Haenam, Jeollanam-do, and there were 8-59 (mean 28.4) metacrcariae per infected crayfish. These results suggest that P. westermani metacerariae are still transmitted by crayfish enzootically in southern Korea, and that freshwater crabs may transmit metacercariae only on rare occasions.

• Parasites, Hosts and Diseases
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• v.29 no.4
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• pp.397-402
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• 1991

Paragonimus westermani is a common fluke in Korea. The present study aimed to determine serum total IgE and specific IgG levels in experimental paragonimiasis of rats. Each Wistar rat was inoculated orally with 20~25 metacercariae of P. westermani from Cambaroides similis. Before and after infection(1,2,3,4,6,8 weeks) of P. westermani, the blood was collected from the retro- orbital venous plexus of rats and kept serum at $-70^{\circ}C$. Serum total IgE and specific IgG levels were determined by the capture and conventional enzyme-linked immunosorbent assay, respectively. The results were as follows; 1. Serum IgE values were increased to 0. 18${\pm}$0.042 at 2 weeks, $0.28{\pm}0.151$ at 4 weeks and 0.43${\pm}0.055$ at 8 weeks after infection. The absorbances of non-infected rats ranged $0.07{\pm}0.021~0.12{\pm}0.025$. 2. Specific IgG values were slightly increased at 3 weeks ($0.20{\pm}$0.032) and gradually increased up to 8 weeks($0.31{\pm}0.067$) after infection. The absorbances of non-infected rats ranged $0.11{\pm}0.035~0.18{\pm}0.019$. The present results suggested that p. westermani could elevate serum IgE and specific IgG antibodies in Wistar rats which were not a good definitive host.

• Parasites, Hosts and Diseases
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• v.29 no.1
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• pp.43-54
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• 1991

An in vitro immune effector mechanism against the target encysted metacercariae of Paragonimus westermani was demonstrated in the rat system. Peritoneal exudate cells, mainly macrophages from normal rats, showed adherence to and killing of encysted metacercariae of p. westermani in the presence of complement-independent serum from rats infected with Paragonimus metacercariae. These reactions were specific for the excysted metacercariae, as tissue-migrating juvenile worms were not affected. Damage of encysted metacercariae of p. westermani due to antibody and macrophages was assessed by morphological observation, by cell adherence reaction and by the use of vital dyes. frypan blue dye exclusion proved to be a reliable indicator of judging metacercarial viability. Electron microscopic studies demonstrated that macrophages reacted with fusty material on the tegumental surface and fine structures in the syncytium of the parasites. The tubular tunnels formed between the basement membrane and muscle layers of the damaged parasites were also noticeable. The relevance of these findings to cellular immunity in the early paragonimiasis was discussed.

• Parasites, Hosts and Diseases
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• v.40 no.2
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• pp.89-92
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• 2002

The cysteine proteases of Paragonimus westermani metacercariae are involved in metacercarial excystment, host immune modulation, and possibly in tissue penetration. In order to clarify the origin of the enzymes, 28 and 27 kDa cysteine proteases in metacercarial excretory-secretory products were purified through the FPLC system using Mono Q column chromatography. The polyclonal antibodies to the enzymes were produced in BALB/c mice. Immunolocalization studies revealed that both cysteine proteases were distributed at the linings of excretory bladder and excretory concretions of the metacercariae. It was suggested that the excretory epithelium of P. westermani undertake the secretory function of metacercarial cysteine proteases, in addition to its role as a route for eliminating waste products.