Infection and biogeographical characteristics of Paragonimus westermani and P. skrjabini in humans and animal hosts in China: A systematic review and meta-analysis.

BACKGROUND: Paragonimiasis, primarily caused by Paragonimus westermani and P. skrjabini in China, is a common food-borne parasitic zoonosis. However, the national distribution of Paragonimus spp. infection and its associated environmental determinants remain poorly understood. In this paper, we summarize the infection of P. westermani and P. skrjabini and describe key biogeographical characteristics of the endemic areas in China. METHODS: Data on Paragonimus infection in humans and animal hosts were extracted from eight electronic databases, including CNKI, CWFD, Chongqing VIP, SinoMed, Medline, Embase, PubMed, and Web of Science. A random-effects meta-analysis model was used to estimate the pooled prevalence. All survey locations were georeferenced and plotted on China map, and scatter plots were used to illustrate the biogeographical characteristics of regions reporting Paragonimus infection. RESULTS: A total of 28,948 cases of human paragonimiasis have been documented, with 2,401 cases reported after 2010. Among the 11,443 cases with reported ages, 88.05% were children or adolescents. The pooled prevalence of P. skrjabini is 0.45% (95% CI: 0.27-0.66%) in snails, 31.10% (95% CI: 24.77-37.80%) in the second intermediate host, and 20.31% (95% CI: 9.69-33.38%) in animal reservoirs. For P. westermani, the pooled prevalence is 0.06% (95% CI: 0.01-0.13%) in snails, 52.07% (95% CI: 43.56-60.52%) in the second intermediate host, and 21.40% (95% CI: 7.82-38.99%) in animal reservoirs. Paragonimus are primarily distributed in regions with low altitude, high temperature, and high precipitation. In northeastern China, only P. westermani infections have been documented, while in more southern areas, infections of both P. westermani and P. skrjabini have been reported. CONCLUSIONS: Paragonimiasis remains prevalent in China, particularly among children and adolescents. Variations exist in the intermediate hosts and geographical distribution of P. westermani and P. skrjabini. Additionally, altitude, temperature, and precipitation may influence the distribution of Paragonimus.

A record of juvenile Paragonimus skrjabini miyazakii from the urinary bladder of the Japanese toad, Bufo japonicus formosus.

We found juveniles of Paragonimus in the urinary bladder of a Japanese toad (Bufo japonicus formosus) captured in Kyoto. These were molecularly identified as Paragonimus skrjabini miyazakii Kamo, Nishida, Hatsushika et Tomimura 1961. This is the first report of P. s. miyazakii found in anuran hosts in Japan, indicating that anurans can be paratenic hosts of P. s. miyazakii, as is also the case for Paragonimus skrjabini skrjabini in China. This finding suggests that definitive hosts of P. s. miyazakii can be infected by eating not only crabs or mammal paratenic hosts, but also anurans.

Dynamic transcriptome landscape of Paragonimus proliferus developmental stages in the rat lungs.

Paragonimus proliferus, a lung fluke of the genus Paragonimus, was first reported in Yunnan province, China. P. proliferus can infect Sprague-Dawley (SD) rats and cause lung damage, but there is still no direct evidence of human infection. Until now, there has been a lack of studies on P. proliferus parasitism and development in mammalian lung tissue. The aim of this study was to perform transcriptomic profiling of P. proliferus at different developmental stages. SD rats were infected with P. proliferus metacercariae obtained from crabs; worms isolated from the lungs at different time points as well as metacercariae were subjected to whole transcriptome sequencing. Overall, 34,403 transcripts with the total length of 33,223,828 bp, average length of 965 bp, and N50 of 1833 bp were assembled. Comparative analysis indicated that P. proliferus, similar to other Paragonimus spp., expressed genes related to catabolism, whereas P. proliferus-specific transcripts were related to the maintenance of cellular redox homeostasis, sensitivity to bacteria, and immune response. Transcriptional dynamics analysis revealed that genes involved in the regulation of catabolism and apoptosis had stable expression over the P. proliferus life cycle, whereas those involved in development and immune response showed time-dependent changes. High expression of genes associated with immune response corresponded to that of genes regulating the sensitivity to bacteria and immune protection. We constructed a P. proliferus developmental model, including the development of the body, suckers, blood cells, reproductive and tracheal systems, lymph, skin, cartilage, and other tissues and organs, and an immune response model, which mainly involved T cells and macrophages. Our study provides a foundation for further research into the molecular biology and infection mechanism of P. proliferus.

Molecular identification of morphologically similar microcercous cercariae of two trematode families, Paragonimidae and Troglotrematidae, concurrently found in the same snail species of the subfamily Triculinae.

Microcercous cercariae possess a very short tail and are produced by digenean species of several families including medically important species, such as members of the genera Paragonimus Braun, 1899, Nanophyetus Chapin, 1927 and Troglotrema Odhner, 1914. During our survey of cercariae of Paragonimus spp. in Vietnam, we found microcercous cercariae from ten (0.29%) out of 3,400 snails of Triculinae gen. sp. 2. They were morphologically and molecularly analysed for species identification. The molecular analysis, based on ITS2 sequences, revealed two distinct species: four specimens were identical to Paragonimus proliferus Hsia et Chen, 1964 (Paragonimidae Dollfus, 1939), and the other six specimens were closest to members of the family Troglotrematidae Odhner, 1914 and were temporarily named Troglotrematidae gen. sp. Morphologically, cercariae of the two species found in this study are similar to each other in their gross characteristics but can be distinguished from one another by subtle morphological details. The cercaria of P. proliferus has an I-shaped excretory bladder and does not have mucous gland cells. In contrast, that of Troglotrematidae gen. sp. has a Y-shaped excretory bladder and mucous gland cells. Besides, the redia of P. proliferus is elongate with a short intestine and contains 5-6 cercariae whereas that of Troglotrematidae gen. sp. is more round with a longer intestine and harbours 3-4 cercariae. Our results have shown the importance of the shape of the excretory bladder and the presence/absence of mucous gland cells of the cercaria as well as the shape and size of the redia, and its intestinal length as valuable taxonomic characters of intramolluscan trematode larvae. In addition, the finding of similar microcercous cercariae of different species in the same snail species suggests that careful attention to morphological details is required in the differentiation of Paragonimus cercariae and those of closely related species.

Asymptomatic Human Paragonimiasis among the Karen People in Tak Province, Thailand: A Case Report.

During the mobile clinic activities in Tak Province, Thailand, Paragonimus sp. eggs were found in a fecal sample of a 72-year-old Karen resident. Paragonimus DNA was amplified from the stool sample and identified to P. heterotremus. The patient did not have any symptoms. Apparent pulmonary lesion was not found on the chest X-ray. The patient admitted habitual consumption of semi-cooked or roasted waterfall crabs for several years. The waterfall crabs collected from stream near the village were found negative for Paragonimus metacercariae. In northern Thailand, paragonimiasis remains as one of the public health concerns and should be ruled out for asymptomatic pulmonary patients.

Identification of suspected paragonimiasis-endemic foci using a questionnaire and detection of Paragonimus ova using the Ziehl-Neelsen technique in Zamboanga Region, the Philippines.

Improving paragonimiasis surveillance, which is crucial for disease control, requires adopting new tools and techniques useful in mapping endemic areas. This study aimed to (1) develop a questionnaire to identify suspected paragonimiasis-endemic foci, (2) describe the epidemiology of paragonimiasis, and (3) evaluate Ziehl-Nielsen Staining technique (ZNS) in detecting Paragonimus ova. The questionnaire, which municipal health officers filled out, was based on proposed site inclusion criteria utilized in the integrated tuberculosis (TB)-paragonimiasis surveillance and control project. Newly deployed medical technologists in Zamboanga Region underwent training, which included laboratory diagnosis of paragonimiasis using preserved and fresh specimens and an integrated tuberculosis-paragonimiasis survey in nine selected barangays (villages). Paragonimiasis cases were found in seven out of the nine barangays identified by the questionnaire. Of the 373 patients, three (0.80%) were TB-positive, and 29 (7.77%) were paragonimiasis-positive. The highest paragonimiasis prevalence (27%) was found in Barangay Libato. Ziehl-Neelsen Staining technique (ZNS) correctly detected 8 out of the 29 samples positive (sensitivity - 27.59%; 95% CI: 12.73-47.24%) and all the 334 samples negative (specificity - 100%; 95% CI: 98.90-100%) for Paragonimus ova. The questionnaire may be improved by refining the inclusion criteria. In paragonimiasis-endemic areas, the ZNS and the NaOH concentration technique may be used for detecting Paragonimus ova. Modifying the ZNS, for instance by including a concentration step, may improve its sensitivity. The model for the integrated capacity building of health workers and surveillance and research demonstrated in this project may contribute to improving surveillance and control of paragonimiasis and other neglected tropical diseases.

Paragonimiasis: Neglected, Re-Emerging or Expanding Frontiers. Lessons from a Case Presenting in Jos, Plateau State.

BACKGROUND AND OBJECTIVES: Paragonimiasis is endemic in Eastern Nigeria. An upsurge was recorded after the Nigeria/Biafra war as protein lack in Biafra forced people to eat fresh water crabs. Its protean manifestations create confusion with several diseases. Elimination was assumed after a while and suspicion index fell. The interest in reporting this case follows its presentation outside the traditional endemic zone. RESULTS: The patient, though living in Eastern Nigeria and manifesting several pointers of Paragonimiasis, was treated as tuberculosis despite negative sputum AFB; without improving. He then presented up-country in Jos where history led to suspicion and confirmation of Paragonimiasis. By this time he had severe cor-pulmonale and died despite treatment. CONCLUSION: In this current economic downturn in Nigeria which may drive people to cheaper protein sources, a high index of suspicion should be raised for paragonimiasis when a patient presents with chronic cough productive of AFB-negative sputum and haemoptysis.

Paragonimiasis pulmonar. Reporte de caso pediátrico / Pulmonary paragonimiasis. Pediatric case report

La paragonimiasis es una parasitosis provocada por varias especies de Paragonimus, un trematodo que se transmite a través del consumo de cangrejos poco cocidos o crudos y que se ha encontrado en áreas tropicales y subtropicales de América, Asia y África. Esta infección afecta, principalmente, los pulmones y provoca manifestaciones clínicas y radiológicas muy similares a la tuberculosis pulmonar, por lo cual siempre debe incluirse dentro del diagnóstico diferencial. Se presenta el caso de una niña escolar de 7 años de edad, hospitalizada con el diagnóstico de paragonimiasis pulmonar, quien presentó evolución favorable luego de recibir tratamiento con triclabendazol.

Paragonimiasis is a parasite infection caused by several species of Paragonimus, a trematode that is transmitted through the consumption of raw or undercooked crabs and that has been found in the subtropical areas of America, Asia and Africa. This infection mainly affects the lungs, causing clinical and radiological manifestations very similar to pulmonary tuberculosis, so it should always be included in the differential diagnosis. We present the case of a 7-year-old school patient, hospitalized with the diagnosis of pulmonary paragonimiasis, who had a favorable evolution after receiving treatment with triclabendazole.

[Pulmonary paragonimiasis. Pediatric case report]. / Paragonimiasis pulmonar. Reporte de caso pediátrico.

Paragonimiasis is a parasite infection caused by several species of Paragonimus, a trematode that is transmitted through the consumption of raw or undercooked crabs and that has been found in the subtropical areas of America, Asia and Africa. This infection mainly affects the lungs, causing clinical and radiological manifestations very similar to pulmonary tuberculosis, so it should always be included in the differential diagnosis. We present the case of a 7-year-old school patient, hospitalized with the diagnosis of pulmonary paragonimiasis, who had a favorable evolution after receiving treatment with triclabendazole.

La paragonimiasis es una parasitosis provocada por varias especies de Paragonimus, un trematodo que se transmite a través del consumo de cangrejos poco cocidos o crudos y que se ha encontrado en áreas tropicales y subtropicales de América, Asia y África. Esta infección afecta, principalmente, los pulmones y provoca manifestaciones clínicas y radiológicas muy similares a la tuberculosis pulmonar, por lo cual siempre debe incluirse dentro del diagnóstico diferencial. Se presenta el caso de una niña escolar de 7 años de edad, hospitalizada con el diagnóstico de paragonimiasis pulmonar, quien presentó evolución favorable luego de recibir tratamiento con triclabendazol.

Paragonimus and paragonimiasis in Asia: An update.

Paragonimiasis, or lung fluke disease, is a typical food-borne parasitic zoonosis caused by infection with trematodes belonging to the genus Paragonimus. More than 50 species of Paragonimus have been reported throughout the world, of which seven valid species infect humans, an estimated one million people annually worldwide. Among the seven species, P. westermani, P. heterotremus, and P. skrjabini/P. s. miyazakii, distributed in Asia, are the most important species as the cause of paragonimiasis. Humans acquire infection through the ingestion of raw, pickled or undercooked freshwater crustaceans, 2nd intermediate hosts, or consuming raw meat of wild boar or deer, paratenic hosts. Infections often occur clustered in foci where dietary habits allow transmission of the parasites. Paragonimiasis typically causes a subacute to chronic inflammatory disease of the lungs. The symptoms, including chronic cough, chest pain, dyspnea and hemoptysis, mimic those of tuberculosis and lung cancer. Serologic tests are commonly used for the diagnosis of paragonimiasis, and Praziquantel is the treatment of choice. In this review, the current status of Paragonimus and paragonimiasis in Asia is outlined based on the latest information and findings. We also summarize current trends of paragonimiasis in Japan, which is one of the most endemic area of paragonimiasis in the world, for the better understanding and control of paragonimiasis.

First report of Paragonimus skrjabini miyazakii metacercariae in Geothelphusa dehaani (Sawagani) occurring in Iwate Prefecture, Japan.

Paragonimiasis is an important food-borne zoonosis caused by Paragonimus flukes and is endemic to western Japan. However, there have been few epidemiological studies in the Tohoku district of northeastern Japan. In this study, Paragonimus metacercariae (mc) was detected in Geothelphusa dehaani (Japanese freshwater crab or Sawagani) in Iwate Prefecture. Out of the 207 Sawagani collected from 35 localities, 12 individuals from six localities were infected with Paragonimus mc. The mc were identified as P. skrjabini miyazakii based on the sequences of nuclear ribosomal internal transcribed spacer 2 and mitochondrial cytochrome c oxidase I. This is the first report of P. s. miyazakii mc infection in Sawagani in Iwate Prefecture.

First intermediate hosts of Paragonimus spp. in Vietnam and identification of intramolluscan stages of different Paragonimus species.

BACKGROUND: Members of the genus Paragonimus require at least three hosts in their life-cycles. The obligatory first intermediate hosts are freshwater snails. In Vietnam, although seven Paragonimus species have been recorded, the natural first intermediate hosts of almost all species have not been confirmed. The aim of this study was, therefore, to investigate snail hosts of Paragonimus species in Vietnam, and to identify Paragonimus species at intramolluscan stages. METHODS: Freshwater snails were collected from streams in Yen Bai and Quang Tri Provinces, where high prevalences of Paragonimus metacercariae in crab hosts have been reported. Snails were morphologically identified and then examined individually for Paragonimus cercariae using shedding and crushing methods. Chaetomicrocercous cercariae, the morphological class to which Paragonimus cercariae belong, were collected for morphological description and molecular species identification by analyses of ITS2 sequences. The infected snail species were identified based on analyses of nucleotide sequences of the cox1 gene. RESULTS: Three snail species were found to be infected with Paragonimus cercariae at low infection rates, ranging between 0.07-1.0%. The molecular analyses identified them as Sulcospira quangtriensis and 2 species of subfamily Triculinae. In a phylogenetic tree, these two triculine snails were related to the genera Gammatricula and Tricula with low posterior probabilities. Thus we named them as Triculinae sp. 1 and Triculinae sp. 2. Cercariae from the three snail species, Sulcospira quangtriensis, Triculinae sp. 1 and Triculinae sp. 2, were molecularly identified as Paragonimus westermani, P. heterotremus and P. proliferus, respectively. The cercariae of the three species are morphologically similar to each other, but their daughter rediae can be distinguished by the length of the intestine and the number of cercariae per redia. The rediae of P. westermani have a long intestine and each contain 6-8 cercariae. In contrast, those of P. heterotremus and P. proliferus have a short intestine and each redia contain 10-12 and 5-6 cercariae, respectively. CONCLUSIONS: Three snail species, Sulcospira quangtriensis, Triculinae sp. 1 and Triculinae sp. 2, serve as the first intermediate hosts of P. westermani, P. heterotremus and P. proliferus, respectively, in Vietnam. The length of the intestine of rediae and the number of cercariae per redia are valuable characteristics for distinguishing between larvae of these Paragonimus species.

Hypolobocera guayaquilensis (Decapoda: Pseudothelphusidae): A New Crab Intermediate Host of Paragonimus mexicanus in Manabí Province, Ecuador.

To determine that Paragonimus sp. is actively transmitted in a tropical area of the Pacific region of Ecuador where human cases of pulmonary paragonimiasis have recently been documented, a total of 75 freshwater crabs were collected from 2 different streams in the Pedernales area of Manabí Province, Ecuador. All collected crabs were identified as Hypolobocera guayaquilensis based on morphological characteristics of the male gonopods. The hepatopancreas of each crab was examined by compressing it between 2 glass plates followed by observation under a stereomicroscope. Excysted Paragonimus metacercariae were detected in 39 (52.0%) crabs and their densities varied from 1 to 32 per infected crab. There was a positive relationship between crab size and metacercarial density. Sequences of the second internal transcribed spacer region of the ribosomal RNA gene of the Paragonimus metacercariae obtained in this study were identical to those of Paragonimus mexicanus deposited in the DDBJ/EMBL/GenBank database. Thus, the present study is the first to confirm that the crab species H. guayaquilensis is the second intermediate host of P. mexicanus in Manabí Province, Ecuador. Because this crab might be the possible source of human infections in this area, residents should pay attention to improper crab-eating habits related with a neglected parasitic disease, i.e., paragonimiasis.

Incidence of paragonimiasis in Chongqing China: a 6-year retrospective case review.

Paragonimiasis is an important infectious disease in Chongqing, China. However, no epidemiological surveys of paragonimiasis have been carried out in Chongqing since it became a municipality in 1997. We conducted a retrospective case review of 683 patients who were referred to our laboratory and diagnosed as having paragonimiasis during 2010-2015. Patients were diagnosed with paragonimiasis based on immunodiagnostic tests in addition to clinical and laboratory findings. Patient data extracted from the epidemiologic form were analysed. The majority of patients were distributed on the east side of the Wujiang River, which belongs to the Three Gorges Reservoir region. Consumption of raw or undercooked freshwater crab or crayfish in the family Cambaridae was the main reason for infection. Notably, more than 50·0% of patients were diagnosed between March and July, indicating that serious clinical symptoms only appear approximately 6 months post-infection. Paragonimiasis remains a public health issue in Chongqing, and an epidemiological study of Paragonimus in the Three Gorges region is strongly recommended.

Infection with Paragonimus westermani of boar-hunting dogs in Western Japan maintained via artificial feeding with wild boar meat by hunters.

Infection of boar-hunting dogs with Paragonimus westermani was investigated in Western Japan. Blood and rectal feces were collected from 441 dogs in the three districts (205 in Kinki, 131 in Chugoku and 105 in Shikoku District). In a screening ELISA for serum antibody against P. westermani antigen, 195 dogs (44.2%) showed positive reaction. In the 195 dogs, 8 dogs were found excreting P. westermani eggs after molecular analysis of fecal eggs, and additional 7 were identified serologically for the parasite infection because of their stronger reactivity against P. westermani antigen than against antigens of other species of Paragonimus. A spatial analysis showed that all of the P. westermani infections were found in Kinki and Chugoku Districts. In this area, dogs' experience of being fed with raw boar meat showed high odds ratio (3.35) to the sero-positivity in the screening ELISA, and the frequency of such experiences was significantly higher in sero-positive dogs. While clear relationship was not obtained between predation of boars by dogs during hunting and their sero-positivity. Therefore, it is suggested that human activity of feeding with wild boar meat is the risk factor for P. westermani infection in boar-hunting dogs. Considering that hunting dogs could play as a major definitive host and maintain the present distribution of P. westermani in Western Japan, control measures for the infection in hunting dogs, such as prohibition of raw meat feeding and regular deworming, should be undertaken.

A Case of Ectopic Paragonimiasis in a 17th Century Korean Mummy.

Archaeoparasitological studies on fossilized feces obtained from Joseon Dynasty (1392-1910 CE) mummies have provided invaluable data on the patterns of parasitic infection in pre-modern Korean societies. In our recent radiological investigation of a 17th century Joseon mummy discovered in Cheongdo (South Korea), we located a liver mass just below the diaphragm. Anatomical dissection confirmed the presence of a mass of unknown etiology. A subsequent parasitological examination of a sample of the mass revealed a large number of ancient Paragonimus sp. eggs, making the current report the first archaeoparasitological case of liver abscess caused by ectopic paragonimiasis.