Pleuropulmonary paragonimiasis due to Paragonimus heterotremus: molecular diagnosis, prevalence of infection and clinicoradiological features in an endemic area of northeastern India

The role of helminths in the development of non-communicable diseases

Non-communicable diseases (NCDs) like cardiovascular disease, chronic respiratory diseases, cancers, diabetes, and neuropsychiatric diseases cause significant global morbidity and mortality which disproportionately affect those living in low resource regions including low- and middle-income countries (LMICs). In order to reduce NCD morbidity and mortality in LMIC it is imperative to understand risk factors associated with the development of NCDs. Certain infections are known risk factors for many NCDs. Several parasitic helminth infections, which occur most commonly in LMICs, have been identified as potential drivers of NCDs in parasite-endemic regions. Though understudied, the impact of helminth infections on the development of NCDs is likely related to helminth-specific factors, including species, developmental stage and disease burden. Mechanical and chemical damage induced by the helminth in combination with pathologic host immune responses contribute to the long-term inflammation that increases risk for NCD development. Robust studies from animal models and human clinical trials are needed to understand the immunologic mechanisms of helminth-induced NCDs. Understanding the complex connection between helminths and NCDs will aid in targeted public health programs to reduce helminth-induced NCDs and reduce the high rates of morbidity that affects millions of people living in parasite-endemic, LMICs globally.

Food safety in fisheries: Application of One Health approach

Fisheries comprise the fastest growing sector meeting the global protein requirements. Being an affordable enterprise, it is considered a safe source of food and the muscles of healthy fishes are almost sterile. However, a multitude of hazards (biological, chemical, and environmental) can be introduced into aquaculture throughout the production and supply chain. Also, it can originate from unsuitable farming practices, environmental pollution, and socio-cultural habits prevailing in various regions. Hence, with an increasing global population and demands for aquacultural products, assessment and regulation of food safety concerns are becoming significantly evident. Ensuring safe, secure, affordable, and quality food for all in a global context is pragmatically difficult. In this context, it is quite imperative to understand the ecology and dynamics of these hazards throughout the entire production chain in a One Health approach. Here, we discuss the issues and challenges faced in the fisheries sector as a whole and the need for a One Health approach to overcome such hurdles.

Genetic differentiation of Southeast Asian Paragonimus Braun, 1899 (Digenea: Paragonimidae) and genetic variation in the Paragonimus heterotremus complex examined by nuclear DNA sequences

Southeast Asian lung flukes, the causative agents of human and animal paragonimiasis, comprise at least 14 species. Of these, seven species; Paragonimus bangkokensis, P. harinasutai, P. macrorchis, P. siamensis, P. westermani, P. heterotremus and P. pseudoheterotremus were studied. Two regions of domain 1 of taurocyamine kinase; TkD1 (exon) and TkD1Int2 (intron 2), were used as genetic markers for elucidating their genetic differentiation, genetic variation, and heterozygosity. The TkD1 region was conserved between these species but can potentially be used to differentiate all seven species. However, the TkD1Int2 region had a high level of polymorphism, which is suitable for investigation of genetic variation within or between closely related species, especially P. heterotremus and P. pseudoheterotremus as well as for a phylogenetic analyses of the genus Paragonimus. Heterozygosity was mostly observed in DNA samples extracted from adult P. heterotremus including samples taken from sputum of paragonimiasis patients, whereas DNA extracted from metacercariae was not, except in the samples from Myanmar. Our findings provide evidence of DNA recombination and incomplete lineage sorting of P. heterotremus and P. pseudoheterotremus in TkD1Int2, which suggesting gene flow between these two species.

An outbreak of Paragonimus westermani infection among Cambodian technical intern trainees in Japan, exhibiting various extrapulmonary lesions

We encountered an outbreak of paragonimiasis among Cambodian technical intern trainees (TITs) at a food-processing factory in Fukuoka, Japan. The patients were 20-28 years old, seven females and two males, who had been in Japan for one to four years. All of them had consumed raw or undercooked Japanese mitten crab they purchased at a local grocery store near their training place. CT images showed multiple lesions not only in the lungs but in the extrapulmonary organs as well, such as subcutaneous tissues, abdominal muscles, and mesentery, in most of the patients. Their medical records indicated that all of them acquired infection in Japan, not in Cambodia. Diagnosis was made serologically and the patients were treated with praziquantel successfully. Foreign workers and TITs are increasing in Japan so rapidly, that food borne-infections, including paragonimiasis, should be considered in people from developing countries who have exotic dietary habits.

Paragonimus heterotremus Chen et Hsia, 1964 (Digenea: Paragonimidae): species identification based on the biological and genetic criteria, and pathology of infection

As a result of the experimental infection of rats with metacercariae of Paragonimus heterotremus Chen et Hsia, 1964 from crabs (Potamiscus tannanti) caught in Yen Bai province, Vietnam, it was found that worms migrated into the lungs, to the liver and less frequently to the tissue that lines body cavities of the hosts, where they reached the adult stage, but in the muscles, worms stayed at the larval stage. Studies have shown that for P. heterotremus, rats can simultaneously play the role of the final and paratenic host; herewith, an infection with the trematode of this species can lead to the development of three forms of paragonimiasis: pulmonary, hepatic and muscular. Eggs from the adult worms localised in the liver, unlike eggs from the adult worms localised in the lungs, were not excreted into the external environment, but accumulated inside the organ. Histology and description of changes, which take place on the external surface of organs affected with P. heterotremus, are given in this study. Based on the behavioural characteristics of worms during rat infection and molecular genetic data, we established that worms from Vietnam and India should be assigned to different species of Paragonimus. P. heterotremus distribution is limited to the territory of the Southeast China, Northern Vietnam, Laos and Thailand.

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.

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver, and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods, and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In this chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

Diagnosis and surgical management of pericardial effusion due to paragonimiasis

OBJECTIVES

The pericardial effusion (PE) caused by paragonimiasis is rarely reported. This study aims to present experience in the diagnosis and surgical management of PE due to paragonimiasis.

METHODS

Medical records of 57 children who were diagnosed with PE due to paragonimiasis and underwent surgery at Children's Hospital of Chongqing Medical University between January 2012 and August 2018 were retrospectively reviewed.

RESULTS

The average age of this group was 7.6 ± 3.0 years. Patients were mainly from Chongqing and Sichuan areas. ELISA for Paragonimus skrjabini in all 57 patients showed positive results. Moderate or large PE were identified in 12 and 45 patients, respectively. All patients underwent surgery either by pericardectomy or thoracoscopic surgery. Pathological exams indicated massive eosinophil infiltration in all 57 specimens. After 3-4 courses of praziquantel therapy, the clinical outcomes were satisfactory.

CONCLUSIONS

Typical endemic history, eosinophilia and multiple serous effusion raise suspicions of paragonimiasis. Once moderate to large PE is identified in patients with paragonimiasis, surgical treatment is necessary.

Paragonimiasis

Paragonimiasis is a zoonotic disease caused by lung flukes of the genus Paragonimus. Humans usually become infected by eating freshwater crabs or crayfish containing encysted metacercariae of these worms. However, an alternative route of infection exists: ingestion of raw meat from a mammalian paratenic host. Adult worms normally occur in pairs in cysts in the lungs from which they void their eggs via air passages. The pulmonary form is typical in cases of human infection due to P. westermani, P. heterotremus, and a few other species (Table 5.1). Worms may occupy other sites in the body, notably the brain, but lung flukes have made their presence felt in almost every organ. Ectopic paragonimiasis is particularly common when infection is due to members of the P. skrjabini complex (Table 5.1). Human paragonimiasis occurs primarily in the tropics and subtropics of Asia, Africa, and the Americas, with different species being responsible in different areas (Table 5.1).

Epidemiology of Trematode Infections: An Update

Digenetic trematodes infecting humans are more than 91 species which belong to 46 genera all over the world. According to their habitat in definitive hosts, they are classified as blood flukes (Schistosoma japonicum. S. mekongi, S. mansoni, S. haematobium, and S. intercalatum), liver flukes (Clonorchis sinensis, Opisthorchis viverrini, O. felineus, Metorchis conjunctus, M. bilis, M. orientalis, Fasciola hepatica, F. gigantica, Dicrocoelium dendriticum, and D. hospes), lung flukes (Paragonimus westermani, P. heterotremus, P. skrjabini, P. miyazakii, P. kellicoti, P. mexicanus, P. africanus, and P. uterobilateralis), throat fluke (Clinostomum complanatum), pancreatic fluke (Eurytrema pancreaticum), and intestinal flukes (Metagonimus yokogawai, M. miyatai, M. takahashii, Heterophyes nocens, H. heterophyes, Haplorchis taichui, H. pumilio, H. yokogawai, Centrocestus formosanus, Echinostoma revolutum, E. ilocanum, Isthmiophora hortensis, Echinochasmus japonicus, E. lilliputanus, Artyfechinostomum malayanum, A. sufrartyfex, A. oraoni, Fasciolopsis buski, Gymnophalloides seoi, Neodiplostomum seoulense, Caprimolgorchis molenkampi, Phaneropsolus bonnei, and Plagiorchis muris). The mode of transmission to humans includes contact with cercariae contaminated in water (schistosomes) and ingestion of raw or improperly cooked fish (liver and throat flukes, heterophyids, and echinostomes), snails (echinostomes and gymnophallids), amphibia, reptiles (neodiplostomes), aquatic vegetables (amphistomes), or insect larvae or adults (plagiorchiids, lecithodendriids, and pancreatic fluke). Praziquantel has been proved to be highly effective against most species of trematode infections except fascioliasis. Epidemiological surveys and detection of human infections are required for better understanding of the geographical distribution and endemicity of each trematode species.

Estimation of disability weight for paragonimiasis: a systematic analysis

Background

Paragonimiasis, caused by helminths of the genus Paragonimus spp., is a neglected tropical disease. Human suffering from paragonimiasis is often misunderstood and its quantification by the disability weight of the disability-adjusted life years largely varies in different global burden of disease (GBD) estimates. This paper is to systematically review clinical paragonimiasis cases and requantify the disability weight of human paragonimiasis.

Methods

A systematic analysis was conducted using articles from the following databases: PubMed, Institute for Scientific Information Web of Science, China National Knowledge Infrastructure, the Chinese scientific journal databases Wanfang Data and CQVIP, Africa Journal Online, and the System for Information on Grey Literature in Europe. Search terms were the combination of “paragonim*” with “clinical” or “infection”. Only articles fulfilling the following conditions were recruited for this study: the occurrence of clinical signs and symptoms of paragonimiasis in human beings were reported; diagnosis was confirmed; no comorbidities were reported; the reviewed clinical cases or epidemiological findings were not already included in any other articles. The information and frequencies of paragonimiasis outcomes from included articles using predefined data fields were extracted two times by two separate individuals. Outcome disability weights were selected mainly from the GBD 2004 and GBD 2013 datasets. Frequencies and disability weights of paragonimiasis outcomes were modelled into a decision tree using the additive approach and multiplicative approach, respectively. Monte Carlo simulations were run 5000 times for an uncertainty analysis.

Results

The disability weight estimates of paragonimiasis were simulated with 5302 clinical cases from 80 general articles. The overall disability weight was estimated at 0.1927 (median 0.1956) with a 95% uncertainty interval (UI) of 0.1632–0.2378 using the additive approach, and 0.1791 (median 0.1816) with a 95% UI of 0.1530–0.2182 using the multiplicative approach. The simulated disability weights of Paragonimus westermani cases were higher than that of P. skrjabini cases. Lung outcomes and headache were the top two contributors to disability weight for both species.

Conclusions

The use of paragonimiasis disability weight needs to be reconsidered with regard to availability of morbidity data and species variation. Calculating the disease burden of paragonimiasis requires further modification and thus has considerable implications for public health prioritization in research, monitoring, and control.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0485-5) contains supplementary material, which is available to authorized users.

Paragonimiasis in Children in Southwest China: A retrospective case reports review from 2005 to 2016

BACKGROUND

Paragonimiasis infection has no specific symptoms or typical radiologic findings, leading to the possibility of misdiagnosis. Thus, the objective of this study was to analyze clinical and radiological features, and treatment outcome of paragonimiasis in children in Southwest China to improve the awareness of this disease.

METHODS

We retrospectively reviewed the records of children diagnosed with paragonimiasis in West China Second University Hospital between 2005 and 2016. The confirmed diagnosis of paragonimiasis was based on epidemiology history and seropositivity for paragonimiasis and/or detection of paragonimus eggs. Clinical, laboratory, and imaging findings of patients were examined in order to summarize risk factors, clinical characteristics, and treatment outcomes of these patients.

RESULTS

A total of 123 patients were included; of them 112 (91.1%) lived in villages and 72 (58.5%) had a history of consuming freshwater crabs. Patients with paragonimiasis most frequently showed respiratory symptoms, including cough (26.0%, 32/123) and tachypnea (16.3%, 20/123), and gastrointestinal symptoms, including abdominal pain (26.8%, 33/123), abdominal distention (22.8%, 28/123), and vomiting (13.0%, 16/123). Laboratory examination showed elevated white blood cell (WBC) counts in the peripheral blood in 89 (72.4%) patients and eosinophilia in 102 (82.9%) patients. Tuberculosis (TB) coinfection was found in 4 (3.3%) patients. Main imaging findings included: effusions (90.4%), lymphadenopathy (40.4%), pulmonary ground-glass opacities (36.2%), cystic lesions (18.1%), and pleural thickening (17.0%). Twenty-nine patients (23.6%) received more than 1 course of praziquantel (PZQ). Additionally, 4 (19.0%) of 21 patients who were discharged from the hospital without complete treatment required rehospitalization for residual serous effusions. Moreover, patients from pericardial effusion group showed longer hospital stays and less elevated WBC counts than those from nonpericardial effusion group.

CONCLUSION

Paragonimiasis should be considered in patients from endemic areas, especially in those with gastrointestinal and/or respiratory symptoms, elevated WBC count, eosinophilia, and serous effusions. Additionally, longer hospital stay may be necessary in cases of paragonimiasis associated with pericardial effusions.

A singleplex real-time fluorescence resonance energy transfer PCR with melting curve analysis for the differential detection of Paragonimus heterotremus, Echinostoma malayanum and Fasciola gigantica eggs in faeces

BACKGROUND

Because the eggs of Paragonimus, Echinostoma and Fasciola are very similar in size and shape, it is difficult to distinguish and accurately identify species by the morphology of their eggs, which is a standard diagnostic method.

METHODS

In this study, a novel assay combining a real-time fluorescence resonance energy transfer PCR and melting curve analysis using one set of primers and fluorophore-labelled hybridization probes specific for the 28S rDNA region was developed for the molecular detection of Paragonimus heterotremus, Echinostoma malayanum and Fasciola gigantica eggs.

RESULTS

This assay could detect and distinguish P. heterotremus, E. malayanum and F. gigantica DNA with the distinct melting temperature (Tm) values of 57.99±0.08, 62.12±0.15 and 74.10±0.18, respectively. The assay can also be used to detect and distinguish DNA from P. bangkokensis, P. harinasutai, P. machorchis, E. revolutum, Hypodereum conoideum and F. hepatica, which have different Tm values. The sensitivity of this assay enabled the detection of one egg of P. heterotremus, E. malayanum or F. gigantica per 100 mg of faeces. In addition, the specificity testing showed no fluorescence signal for other parasites.

CONCLUSIONS

Due to the sensitivity and specificity of our assay in detecting P. heterotremus, E. malayanum and F. gigantica, our method could be used to accurately diagnose these three medically important parasitic groups and has potential implications for molecular epidemiological investigations of human and/or animal infections.

Declining prevalence of pulmonary paragonimiasis following treatment & community education in a remote tribal population of Arunachal Pradesh, India

Background & objectives:

In India, human pulmonary paragonimiasis is an important public health problem in the northeastern (NE) region. In 2005 we reported a hyperendemic focus of paragonimiasis in a remote tribal village in the hills of Changlang district in Arunachal Pradesh. The community was made aware of the disease and all active cases were treated. This study was aimed to assess the decline in the prevelance of paragonimiasis in the same area after a re-survey done in 2011 after a gap of six years.

Methods:

Re-surveys were carried to determine the reduction in the prevalence of paragonimiasis. Community education was given to the villagers to raise their awareness about paragonimiasis. A total of 624 individuals including 301 children (age < 15 yr) were included in the study. Sputum and stool samples were examined for eggs of lung flukes. Serum samples were screened for IgG antibodies against lung fluke antigen by ELISA.

Results:

A significant (P<0.001) decline in the prevalence of paragonimiasis was found. There was decline in both ELISA positivity and egg positivity. Antibody positivity against excretory-secretary (ES) antigen in children (age ≤ 15 yr) fell down from earlier 51.7 to 15.9 per cent and in individuals 16 - 30 yr of age the serological prevalence fell down from 22.4 to 8.2 per cent and in individuals aged ≥ 31 yr, the decline in prevalence was from 15.3 to 3.7 per cent. Gender-wise analysis revealed that the decline in ELISA positivity was similar in both genders and fell down from 33.9 to 11.5 per cent in males and from 29.8 to 10.7 per cent in females. Similarly, there was a significant decline rate in egg positivity also.

Interpretation & conclusions:

The strategy of hotspot targeted active paragonimiasis case detection and treatment of infected cases together with community education appears to be feasible methods to achieve control of paragonimiasis in this region.

Preparation of colloidal gold immunochromatographic strip for detection of Paragonimiasis skrjabini

Background

Paragonimiasis is a food-borne trematodiasis, a serious public health issue and a neglected tropical disease. Paragonimus skrjabini is a unique species found in China. Unlike paragonimiasis westermani, it is nearly impossible to make a definitive diagnosis for paragonimiasis skrjabini by finding eggs in sputum or feces. Immunodiagnosis is the best choice to detect paragonimiasis skrjabini. There is an urgent need to develop a novel, rapid and simple immunoassay for large-scale screening patients in endemic areas.

Methodology/Principal Findings

To develop a rapid, simple immunodiagnostic assay for paragonimiasis, rabbit anti-human IgG was conjugated to colloidal gold particles and used to detect antibodies in the sera of paragonimiasis patients. The synthesis and identification of colloidal gold particles and antibody-colloidal gold conjugates were performed. The size of colloidal gold particles was examined using a transmission electron microscope (TEM). The average diameter of colloidal gold particles was 17.46 nm with a range of 14.32–21.80 nm according to the TEM images. The formation of antibody-colloidal gold conjugates was monitored by UV/Vis spectroscopy. Excretory-secretory (ES) antigen of Paragonimus skrjabini was coated on nitrocellulose membrane as the capture line. Recombinant Staphylococcus protein A was used to prepare the control line. This rapid gold immunochromatographic strip was assembled in regular sequence through different accessories sticked on PVC board. The relative sensitivity and specificity of the strip was 94.4% (51/54) and 94.1% (32/34) respectively using ELISA as the standard method. Its stability and reproducibility were quite excellent after storage of the strip at 4°C for 6 months.

Conclusions/Significance

Immunochromatographic strip prepared in this study can be used in a rapid one-step immunochromatographic assay, which is instantaneous and convenient.

Paragonimiasis

Paragonimiasis is a zoonotic disease caused by lung flukes of the genus Paragonimus. Humans usually become infected by eating freshwater crabs or crayfish containing encysted metacercariae of these worms. However, an alternative route of infection exists: ingestion of raw meat from a mammalian paratenic host. Adult worms normally occur in pairs in cysts in the lungs from which they void their eggs via air passages. The pulmonary form is typical in cases of human infection due to P. westermani, P. heterotremus, and a few other species (Table 5.1). Worms may occupy other sites in the body, notably the brain, but lung flukes have made their presence felt in almost every organ. Ectopic paragonimiasis is particularly common when infection is due to members of the P. skrjabini complex (Table 5.1). Human paragonimiasis occurs primarily in the tropics and subtropics of Asia, Africa, and the Americas, with different species being responsible in different areas (Table 5.1).

Molecular variation in the Paragonimus heterotremus complex in Thailand and Myanmar

Paragonimiasis is an important food-borne parasitic zoonosis caused by infection with lung flukes of the genus Paragonimus. Of the 7 members of the genus known in Thailand until recently, only P. heterotremus has been confirmed as causing human disease. An 8th species, P. pseudoheterotremus, has recently been proposed from Thailand, and has been found in humans. Molecular data place this species as a sister species to P. heterotremus, and it is likely that P. pseudoheterotremus is not specifically distinct from P. heterotremus. In this study, we collected metacercariae of both nominal species (identification based on metacercarial morphology) from freshwater crabs from Phetchabun Province in northern Thailand, Saraburi Province in central Thailand, and Surat Thani Province in southern Thailand. In addition, we purchased freshwater crabs imported from Myanmar at Myawaddy Province, western Thailand, close to the Myanmar-Thailand border. The DNAs extracted from excysted metacercariae were PCR-amplified and sequenced for ITS2 and cox1 genes. The ITS2 sequences were nearly identical among all samples (99-100%). Phylogenies inferred from all available partial cox1 sequences contained several clusters. Sequences from Indian P. heterotremus formed a sister group to sequences from P. pseudoheterotremus-type metacercariae. Sequences of P. heterotremus from Thailand, Vietnam, and China formed a separate distinct clade. One metacercaria from Phitsanulok Province was distinct from all others. There is clearly considerable genetic variation in the P. heterotremus complex in Thailand and the form referred to as P. pseudoheterotremus is widely distributed in Thailand and the Thai-Myanmar border region.

Active detection of tuberculosis and paragonimiasis in the remote areas in North-Eastern India using cough as a simple indicator

One of the essential steps in targeting tuberculosis (TB) intervention is early diagnosis and treatment of patients by reducing the reservoir of infection in the community. In the North-Eastern (NE) region of India pulmonary TB and paragonimiasis are overlapping public health issues. We performed a cross-sectional study in 63 remote villages from the two states Arunachal Pradesh (AP) and Assam to determine the prevalence of undiagnosed TB and paragonimiasis cases using cough as a simple indicator. In AP, 2961 individuals aged five years and above were examined and 1108 (37·4%) were found to have cough for one week or more. Of the 417 individuals who provided sputum, 11 (2·64%) were smear positive for acid-fast bacilli (AFB). All these cases were yet undiagnosed, thus the prevalence of new smear positive TB in AP was 0·37%. In Assam on the other hand 331 (23·5%) subjects out of 1410 individuals who were examined had a cough for one week or more and of the 112 individuals who provided sputum, 13 (11·6%) were smear positive for AFB. The prevalence of new smear positive TB cases was 0·78% in Assam. Sero-positivity of paragonimiasis in coughers of AP was 7·6% (n = 1091), which was significantly higher (p < 0·01) as compared to that in Assam (1·2%, n = 321). The findings of the present study suggest that TB remains a major public health concern in the NE region of India especially in the remote places and there is need to strengthen early case detection of TB.

Metacercarial polymorphism and genetic variation of Paragonimus heterotremus (Digenea: Paragonimidae), and a re-appraisal of the taxonomic status of Paragonimus pseudoheterotremus

Paragonimus heterotremus, which is an important pathogen for human paragonimiasis in Asia, is recognized as having the smallest metacercariae (maximum diameter < 300 μm) of any previously reported Paragonimus species. Recently, P. pseudoheterotremus has been described from Thailand as a new species having metacercariae (about 200 μm) slightly smaller than those of Thai P. heterotremus. In fact, the small size of P. pseudoheterotremus metacercariae is compatible with those of P. heterotremus from India and China. In this study in Vietnam, we found variably sized small metacercariae which are expected to consist of both P. heterotremus and P. pseudoheterotremus. Contrary to expectation, the adult flukes obtained by separate infection of experimental cats with different sized metacercariae were all identified as P. heterotremus, using both morphological and molecular characteristics. The molecular analyses of an extensive collection of P. heterotremus/P. pseudoheterotremus isolates from Asian countries also indicated that genetic distances between different populations of P. heterotremus are even larger than that between P. pseudoheterotremus and P. heterotremus. The haplotype network showed that all P. heterotremus and P. pseudoheterotremus isolates formed a P. heterotremus complex consisting of three groups with strong geographical origins. In addition, the Indian P. heterotremus group is the root of the other P. heterotremus and P. pseudoheterotremus populations. Based on the observed metacercarial polymorphisms and genetic variation in P. heterotremus,P. pseudoheterotremus should be considered a geographically isolated population of the P. heterotremus complex.

Pleuropulmonary paragonimiasis: mimicker of tuberculosis

Infection caused by the lung fluke is endemic in north eastern parts of India. Paragonimus westermani and Paragonimus heterotremus are known to be endemic in eastern Indian states of Manipur and Nagaland. The infection is related to eating habits of the locals and is acquired by ingestion of raw, inadequately cooked crabs or crayfish containing encysted metacercariae which act as second intermediate hosts during the life cycle of the lung fluke. Diagnosis is generally delayed due to lack of suspicion and presentation similar to tuberculosis which is endemic in the population. We report pleuropulmonary paragonimiasis in a soldier from eastern India who presented with chest pain, haemoptysis, and eosinophilia. He gave history of consumption of raw crabs while on leave at his native village in Nagaland. Ova morphologically resembling Paragonimus heterotremus were detected in sputum and bronchoalveolar lavage specimen. Symptoms resolved with praziquantel treatment.

A case of cutaneous paragonimiasis presented with minimal pleuritis

Clinically, paragonimiasis is broadly classified into pulmonary, pleuropulmonary, and extrapulmonary forms. The common extrapulmonary forms are cerebral and cutaneous paragonimiasis. The cutaneous paragonimiasis is usually presented as a slowly migrating and painless subcutaneous nodule. The correct diagnosis is often difficult or delayed or remained undiagnosed until the nodule becomes enlarged and painful and the cause is investigated. We report here a case of cutaneous paragonimiasis in a male child who presented with mild respiratory symptoms. The diagnosis of paragonimiasis was based on a history of consumption of crabs, positive specific serological test, and blood eosinophilia. The swelling and respiratory symptoms subsided after a prescribed course of praziquantel therapy.

Presence of three distinct genotypes within the Paragonimus westermani complex in northeastern India

The name Paragonimus westermani (Kerbert, 1878) is commonly applied to members of a species complex that includes the well-known Asian lung fluke of medical and veterinary importance. Unambiguous molecular and morphological evidence showing the presence of a member of the complex in India has recently been published. In the present study we report the occurrence of 2 more members of the P. westermani complex in northeastern (NE) India. Surveys of the freshwater crabs Maydelliatelphusa lugubris in NE India revealed 2 morphologically distinct types of lung fluke metacercariae. Phylogenetic analyses, using DNA sequences from ITS2, 28S and cox1 gene regions indicate that these lung metacercariae belong to P. westermani complex. Type 1 metacercariae have a more basal position within the complex whereas type 2 metacercariae are closely related to the relatively derived forms of P. westermani from NE Asia (Japan, Korea, China) and Vietnam. A third type of metacercaria (type 3), detected in another crab host, Sartoriana spinigera in Assam, was phylogenetically close to P. siamensis, also a member of the P. westermani group. Molecular evidence has demonstrated the existence of 3 genotypes of lung flukes within the Paragonimus westermani complex in NE India. Two of these were previously unknown.

Molecular identification of a case of Paragonimus pseudoheterotremus infection in Thailand

Paragonimiasis is an important food-borne parasitic zoonosis caused by infection with lung flukes of the genus Paragonimus. In Southeast Asia, Paragonimus heterotremus is the only proven causative pathogen. Recently, a new Paragonimus species, P. pseudoheterotremus, was found in Thailand. This species is genetically similar to P. heterotremus and is considered as a sister species. However, infectivity or pathogenicity of P. pseudoheterotremus to humans remains unclear. We report the first confirmed human pulmonary paragonimiasis case caused by P. pseudoheterotremus infection. After polymerase chain reaction/sequencing of the DNA extracted from Paragonimus eggs in the sputum of the patient, partial internal transcribed spacer 2 and cytochrome c oxidase subunit 1 sequences were approximately identical (98-100%) with those of P. pseudoheterotremus. For P. heterotremus, the partial internal transcribed spacer 2 sequence was approximately identical (99-100%), but the partial mitochondrial cytochrome c oxidase subunit 1 sequence showed a similarity of 90-95%.

Rapid identification of paragonimiasis foci by lay informants in Lao People's Democratic Republic

Background

Paragonimiasis is a food-borne trematodiasis leading to lung disease. Worldwide, an estimated 21 million people are infected. Foci of ongoing transmission remain often unnoticed. We evaluated a simple questionnaire approach using lay-informants at the village level to identify paragonimiasis foci and suspected paragonimiasis cases.

Methodology/Principal Findings

The study was carried out in an endemic area of Lao People's Democratic Republic. Leaders of 49 remote villages in northern Vientiane Province were asked to notify suspected paragonimiasis patients using a four-item questionnaire sent through administrative channels: persons responding positively for having chronic cough (more than 3 weeks) and/or blood in sputum with or without fever. We validated the village leaders' reports in ten representative villages with a door-to-door survey. We examined three sputa of suspected patients for the presence of Paragonimus eggs and acid fast bacilli. 91.8% of village leaders participated and notified a total of 220 suspected patients; 76.2% were eventually confirmed; an additional 138 suspected cases were found in the survey. Sensitivity of village leaders' notice for “chronic cough” and “blood in sputum” was 100%; “blood in sputum” alone reached a sensitivity of 85.7%.

Significance

Our approach led to the identification of three previously unknown foci of transmission. A rapid and simple lay-informant questionnaire approach is a promising low-cost community diagnostic tool of paragonimiasis control programs.

Paragonimiasis is a neglected pulmonary disease provoked by a food-borne trematode parasite. The infection may develop into severe pulmonary disease, often diagnosed with delay and confused with tuberculosis. Globally an estimated 21 millions people are infected. Human infection is acquired through consumption of raw crab, crayfish or wild boar. Typically infections occur clustered in foci of few to several villages where nutritional habits allow transmission. A major challenge for control is to identify the transmission foci. We evaluated a questionnaire approach using lay-informants at the village level to identify paragonimiasis foci and suspected cases. We sent a 4-item questionnaire to 49 village-leaders of a district in rural Lao PDR asking them to report patients with key symptoms of paragonimiasis, i.e. “chronic cough” and “blood in sputum”. The evaluation showed that lay-informants' report had a high sensitivity to identify suspected cases of paragonimiasis using “blood in sputum” as indicator. The approach allowed identifying 3 new, previously unknown foci of transmission in the district. We conclude that lay-informant questionnaires using easily identifiable key symptoms are simple to carry out and are promising low-cost tools for paragonimiasis control.