Anisakiasis Annual Incidence and Causative Species, Japan, 2018-2019.

Using data from 2018-2019 health insurance claims, we estimated the average annual incidence of anisakiasis in Japan to be 19,737 cases. Molecular identification of larvae revealed that most (88.4%) patients were infected with the species Anisakis simplex sensu stricto. Further insights into the pathogenesis of various anisakiasis forms are needed.

[Current Incidence and Contamination Sources of Ascariasis in Japan].

Ascaris lumbricoides or roundworm is one of the key soil-transmitted helminths affecting humans. A small number of infections continue to occur in Japan, suggesting plant foodstuff contamination as the source of infection. To understand the current status of ascariasis incidence and to identify potential sources of infection, we extensively surveyed the available literature and collected data from testing facilities that examined clinical samples or foodstuffs. We observed that from 2002 onwards, there was a decrease in the number of ascariasis cases reported in scientific journals. Data from a clinical testing facility indicated that the number of detected cases declined remarkably from 2009. Foodstuff testing facilities reported that 11 of 10,223 plant foodstuff specimens were contaminated with anisakid nematodes but not with Ascaris. Imported kimchi was suspected as the most probable source of ascarid nematode infection, as one Ascaris egg-positive sample was detected among 60 kimchi samples in a testing facility. Therefore, the sources of Ascaris infection are still not fully known and need to be clarified to establish preventive countermeasures to safeguard Ascaris infections that continue to occur in Japan.

A case of hepatic anisakiasis caused by Pseudoterranova decipiens mimicking metastatic liver cancer.

BACKGROUND: Anisakid nematodes (Anisakis spp. or Pseudoterranova spp.) usually infect gastric or intestinal walls, while they rarely infect in extra-gastrointestinal sites of human body. Generally, Anisakis spp. larvae are highly infected in fish intermediate hosts, whereas Pseudoterranova spp. larvae are very rarely infected. To the best of our knowledge, there have been no reports which have documented cases of hepatic anisakiasis caused by Pseudoterranova spp. This report describes the first documented case of hepatic anisakiasis due to infection with Pseudoterranova decipiens and clinical features of the hepatic anisakiasis through literature review. CASE PRESENTATION: The case was a 28-year-old man with prior history of malignancy who was found to have a hepatic mass mimicking metastatic liver tumor. A new low density area of 20 mm in diameter in liver segment 7 was found on follow-up CT. With suspicious diagnosis of metastatic liver cancer, laparoscopic partial hepatectomy was performed. A pathological examination revealed no evidence of malignancy, but showed necrotic granuloma with eosinophil infiltration and the presence of a larva with Y-shaped lateral cords, which are specific to anisakid larvae. The type of larva was identified as Pseudoterranova decipiens sensu lato using PCR of DNA purified from a fixed granuloma embedded in paraffin. CONCLUSION: The present report is the first to discuss the case of a patient with hepatic anisakiasis caused by Pseudoterranova decipiens. Hepatic anisakiasis is a potential differential diagnosis for hepatic tumors and genetic identification with the PCR method was reliable for obtaining final diagnosis even when the larvae body in the resected specimen collapses with time.

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.

Male-specific pulmonary hemorrhage and cytokine gene expression in golden hamster in early-phase Leptospira interrogans serovar Hebdomadis infection.

Leptospirosis causes severe clinical signs more frequently in men than in women, but the mechanism underlying the gender differences in leptospirosis remains unclear. In this study, petechial hemorrhage was observed in male but not in female hamster lung tissues infected with Leptospira interrogans serovar Hebdomadis at 120 h pi, demonstrating that male hamsters were more susceptible to the development of a severe disease upon Leptospira infection. No leptospiral DNA was detected in the lung tissues at 120 h pi when pulmonary hemorrhage was observed, indicating that pulmonary hemorrhage is attributable to the immune reactions of the host rather than from the direct effect of leptospires. The upregulation of nitric oxide synthase genes in the hamsters without pulmonary hemorrhage, inos and enos in female hamsters at 96 h pi and enos in male animals without hemorrhage at 120 h pi, may suggest that nitric oxide has a suppressive effect on leptospirosis-associated pulmonary hemorrhage.

Paragonimus westermani infection mimicking recurrent lung cancer: A case report.

Herein, we report a case of Paragonimus westermani infection, which required differentiation from recurrent lung cancer. A 66-year old Japanese man with a history of lung cancer who had undergone a lobectomy was referred to our clinic for treatment of cough, sputum, dyspnea, and a right pulmonary nodule. He had previously eaten seafood he visited China. P. westermani infection was confirmed by the presence of antibody against P. westermani antigen in the patient's serum and eggs in his sputum. Eventually, molecular identification by PCR-restriction fragment length polymorphism analysis and sequencing confirmed that the patient was infected with triploid forms of P. westermani.

Anisakiasis mimics cancer recurrence: two cases of extragastrointestinal anisakiasis suspected to be recurrence of gynecological cancer on PET-CT and molecular biological investigation.

BACKGROUND: We report two cases of anisakiasis lesions that were initially suspected to be recurrence of gynecological cancer by positron emission tomography-computed tomography (PET-CT). Both cases were extragastrointestinal anisakiasis that is very rare. CASE PRESENTATION: The first case was a patient with endometrial cancer. At 19 months after surgery, a new low density area of 2 cm in diameter in liver segment 4 was found on follow-up CT. In PET-CT, the lesion had abnormal (18)fluoro-deoxyglucose (FDG) uptake with elevation in the delayed phase, with no other site showing FDG uptake. Partial liver resection was performed. A pathological examination revealed no evidence of malignancy, but showed necrotic granuloma with severe eosinophil infiltration and an irregular material with a lumen structure in the center. Parasitosis was suspected and consultation with the National Institute of Infectious Diseases (NIID) showed the larvae to be Anisakis simplex sensu stricto by genetic examination. The second case was a patient with low-grade endometrial stromal sarcoma (LG-ESS). At 8 months after surgery, swelling of the mediastinal lymph nodes was detected on CT and peripheral T-cell lymphoma was diagnosed by biopsy. A new peritoneal lesion with abnormal FDG uptake was detected on pre-treatment PET-CT and this lesion was increased in size on post-treatment PET-CT. Tumorectomy was performed based on suspected dissemination of LG-ESS recurrence. The findings in a pathological examination were similar to the first case and we again consulted the NIID. The larvae was identified as Anisakis pegreffi, which is a rare pathogen in humans. Having experienced these rare cases, we investigated the mechanisms of FDG uptake in parasitosis lesions by immunohistochemical staining using antibodies to glucose transporter type 1 (GLUT-1) and hexokinase type 2 (HK-2). While infiltrated eosinophils were negative, macrophages demonstrated positive for both antibodies. Therefore, mechanisms behind FDG uptake may involve macrophages, which is common among various granulomas. This is the first report to investigate parasitosis in such a way. CONCLUSION: These cases suggest that anisakiasis is a potential differential diagnosis for a lesion with FDG uptake in PET-CT, and that it is difficult to distinguish this disease from a recurrent tumor using PET-CT alone.

The complete mitochondrial genomes of Gnathostoma doloresi from China and Japan.

Gnathostoma doloresi is one of the neglected pathogens causing gnathostomiasis. Although this zoonotic parasite leads to significant socioeconomic concerns globally, little is known of its genetics and systematics. In the present study, we sequenced and characterized the complete mitochondrial (mt) genomes of G. doloresi isolates from China and Japan. The lengths of the mt genomes of the G. doloresi China and Japan isolates are 13,809 and 13,812 bp, respectively. Both mt genomes encode 36 genes, including 12 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 22 transfer RNA genes. The gene order, transcription direction, and genome content are identical with its congener G. spinigerum. Phylogenetic analyses based on concatenated amino acid sequences of 12 PCGs by Bayesian inference (BI) indicated that G. doloresi are closely related to G. spinigerum. Our data provide an invaluable resource for studying the molecular epidemiology, phylogenetics, and population genetics of Gnathostoma spp. and should have implications for further studies of the diagnosis, prevention, and control of gnathostomiasis in humans and animals.

Rapid detection and identification of four major Schistosoma species by high-resolution melt (HRM) analysis.

Schistosomiasis, caused by blood flukes belonging to several species of the genus Schistosoma, is a serious and widespread parasitic disease. Accurate and rapid differentiation of these etiological agents of animal and human schistosomiasis to species level can be difficult. We report a real-time PCR assay coupled with a high-resolution melt (HRM) assay targeting a portion of the nuclear 18S rDNA to detect, identify, and distinguish between four major blood fluke species (Schistosoma japonicum, Schistosoma mansoni, Schistosoma haematobium, and Schistosoma mekongi). Using this system, the Schistosoma spp. was accurately identified and could also be distinguished from all other trematode species with which they were compared. As little as 10(-5) ng genomic DNA from a Schistosoma sp. could be detected. This process is inexpensive, easy, and can be completed within 3 h. Examination of 21 representative Schistosoma samples from 15 geographical localities in seven endemic countries validated the value of the HRM detection assay and proved its reliability. The melting curves were characterized by peaks of 83.65 °C for S. japonicum and S. mekongi, 85.65 °C for S. mansoni, and 85.85 °C for S. haematobium. The present study developed a real-time PCR coupled with HRM analysis assay for detection and differential identification of S. mansoni, S. haematobium, S. japonicum, and S. mekongi. This method is rapid, sensitive, and inexpensive. It has important implications for epidemiological studies of Schistosoma.

A specific indel marker for the Philippines Schistosoma japonicum revealed by analysis of mitochondrial genome sequences.

In the present study, near-complete mitochondrial (mt) genome sequences for Schistosoma japonicum from different regions in the Philippines and Japan were amplified and sequenced. Comparisons among S. japonicum from the Philippines, Japan, and China revealed a geographically based length difference in mt genomes, but the mt genomic organization and gene arrangement were the same. Sequence differences among samples from the Philippines and all samples from the three endemic areas were 0.57-2.12 and 0.76-3.85 %, respectively. The most variable part of the mt genome was the non-coding region. In the coding portion of the genome, protein-coding genes varied more than rRNA genes and tRNAs. The near-complete mt genome sequences for Philippine specimens were identical in length (14,091 bp) which was 4 bp longer than those of S. japonicum samples from Japan and China. This indel provides a unique genetic marker for S. japonicum samples from the Philippines. Phylogenetic analyses based on the concatenated amino acids of 12 protein-coding genes showed that samples of S. japonicum clustered according to their geographical origins. The identified mitochondrial indel marker will be useful for tracing the source of S. japonicum infection in humans and animals in Southeast Asia.

Molecular detection of Diphyllobothrium nihonkaiense in humans, China.

The cause of diphyllobothriosis in 5 persons in Harbin and Shanghai, China, during 2008-2011, initially attributed to the tapeworm Diphyllobothrium latum, was confirmed as D. nihonkaiense by using molecular analysis of expelled proglottids. The use of morphologic characteristics alone to identify this organism was inadequate and led to misidentification of the species.

Current status of Paragonimus and paragonimiasis in Ecuador.

A review of national and international publications on paragonimiasis in Ecuador, epidemiological records from the Ministry of Public Health and unpublished research data was conducted to summarise the current status of the parasite/disease. The purpose of the review is to educate physicians, policy-makers and health providers on the status of the disease and to stimulate scientific investigators to conduct further research. Paragonimiasis was first diagnosed in Ecuador 94 years ago and it is endemic to both tropical and subtropical regions in 19 of 24 provinces in the Pacific Coast and Amazon regions. Paragonimus mexicanus is the only known species in the country, with the mollusc Aroapyrgus colombiensis and the crabs Moreirocarcinus emarginatus, Hypolobocera chilensis and Hypolobocera aequatorialis being the primary and secondary intermediate hosts, respectively. Recent studies found P. mexicanus metacercariae in Trichodactylus faxoni crabs of the northern Amazon. Chronic pulmonary paragonimiasis is commonly misdiagnosed and treated as tuberculosis and although studies have demonstrated the efficacy of praziquantel and triclabendazole for the treatment of human infections, neither drug is available in Ecuador. Official data recorded from 1978-2007 indicate an annual incidence of 85.5 cases throughout the 19 provinces, with an estimated 17.2% of the population at risk of infection. There are no current data on the incidence/prevalence of infection, nor is there a national control programme.

Miniature pigs as the intermediate host for Taenia asiatica.

Taenia asiatica, utilizing pigs as an intermediate host, degenerates and/or calcifies within a few months after infection in pigs, whereas Taenia solium, also using pigs as an intermediate host, can develop into a mature metacestode within a couple of months and can survive for prolong periods in pigs. This raises the question of whether pigs are suitable intermediate hosts for T. asiatica. The host-parasite relationships between T. asiatica and pig strains, such as infection rates and development of metacestodes, have been reported in previous studies: however, little is known about the pathological changes that occur in T. asiatica metacestodes in pigs. Therefore, in the present study, the pathological changes in T. asiatica within 30 days of infection were observed using CLAWN miniature pigs as model animals. Metacestodes were observed on the diaphragmatic surface and throughout the parenchyma of the pig liver 9 days after infection; however, these metacestodes were surrounded by eosinophilic abscesses, and some had already begun to degenerate. By day 20 and 30 post-infection, metacestodes were surrounded by eosinophilic abscesses and had completely degenerated without forming a scolex. These results indicate that although T. asiatica infected miniature pigs, the metacestodes degenerated owing to strong immune responses from the pigs. Therefore, the CLAWN miniature pig are not a suitable intermediate host for T. asiatica. The possible reasons why T. asiatica metacestodes were degenerated and the potential roles of pigs in transmitting the parasite to humans in T. asiatica-endemic regions are discussed in this study. Additionally, data debating whether pigs are suitable intermediate hosts for T. asiatica are provided.

Molecular identification of Spirometra infections in companion animals and wildlife in Japan.

Spirometra infections in companion animals and wildlife in Japan have been diagnosed based on the morphology of the adult worms and eggs, and the etiological agent has been mainly ascribed to Spirometra erinaceieuropaei. However, recent studies have revealed that two other species, Spirometra mansoni and Spirometra asiana, coexist in Japan. Spirometra asiana is a new species recently discovered in Japan. Although morphological discrimination between these two species is difficult, molecular identification is useful. Therefore, to understand which species commonly parasitizes companion animals and wildlife in Japan, a preliminary study was performed based on mitochondrial DNA analysis. Eleven adult worms examined were identified as S. mansoni, suggesting that S. mansoni infects companion animals and wildlife commonly than S. asiana in Japan.

Description of Spirometra asiana sp. nov. (Cestoda: Diphyllobothriidae) found in wild boars and hound dogs in Japan.

According to the latest taxonomy of Spirometra species, six species (lineages) have been tentatively classified as valid. These species are Spirometra erinaceieuropaei, S. folium, S. mansoni, undescribed Spirometra sp. 1, and S. decipiens complex 1 and 2. Among these species, the undescribed species was first discovered as plerocercoid larvae in wild boars in Japan and further studies have confirmed that this species is a new taxon belonging to the genus Spirometra. Here, we describe Spirometra asiana sp. nov., which is difficult to distinguish morphologically from known Spirometra species. However, it is genetically easily distinct from other Spirometra species, thus facilitating identification. We also emphasize that S. mansoni and S. asiana, but not S. erinaceieuropaei, are etiological agents that cause human sparganosis and/or spirometrosis in Asia.

A Case of Nonagenarian Gastric Anisakiasis with Atypical Presentation.

Introduction: Anisakiasis is a parasitic disease caused by larvae from anisakid nematodes. In recent years, there has been an increase in cases of anisakiasis, a relatively uncommon medical condition. Case Presentation: A 93-year-old woman with chronic heart failure developed hives and nausea 6 h after eating silver flounder sashimi, leading to suspicion of fish allergy. Despite treatment, symptoms persisted and progressed to abdominal pain. An upper gastrointestinal endoscopy revealed an Anisakis larva in her stomach, an unusual finding given her age. After endoscopic removal of the living worm, the patient's symptoms were relieved. Conclusion: A case of atypical anisakiasis in a 93-year-old patient was demonstrated. This case underscores the importance of considering atypical presentations in clinical decision-making.

Prevalence and abundance of Anisakis larvae in ready-to-eat mackerel products in Japan.

The risk of contracting anisakiasis from consuming ready-to-eat (RTE) mackerel products in Japan was investigated by examining the prevalence and abundance of Anisakis simplex and its sibling species in these products. From 2019 to 2021, a total of 448 RTE mackerel products were purchased in Japan. Anisakis larvae were isolated from 244 of the 448 samples (54 %), and live larvae were isolated from 161 of the 448 samples (36 %). In total, 3170 Anisakis larvae, which included 919 live larvae, were isolated. The isolated Anisakis larvae consisted of 3118 A. simplex (s. s.), 27 A. pegreffii, and 25 hybrid genotype (A. simplex [s. s.] × A. pegreffii) larvae. No A. berlandi larvae were isolated. The prevalence of larvae in samples of mackerel caught in the Southern Japan region and Sea of Japan was much lower than that in mackerel caught in other areas. Both the prevalence of Anisakis larvae in all samples and their abundance in larvae-positive samples exhibited specific seasonal variations, being high in spring.

Successful Endoscopic Removal of Anisakis Larva that Deeply Invaded the Gastric Mucosa Using Jumbo Forceps.

Anisakiasis is a parasitic disease caused by the ingestion of raw or uncooked seafood infected with third-stage larvae of anisakid nematodes. Generally, the larvae parasites live at the surface of the mucosa, but in this case, the larva deeply invaded its head into the gastric mucosa and was not removable with conventional biopsy forceps. In our case, we demonstrated the usefulness of jumbo forceps to remove the Anisakis larva in such a situation.

Trichinella T9 in wild bears in Japan: Prevalence, species/genotype identification, and public health implications.

In Japan, the recent series of sporadic outbreaks of human trichinellosis caused by Trichinella (Nematoda: Trichocephalida) has occurred owing to the consumption of raw or insufficiently cooked meat from wild bears. However, the infection status and molecular characteristics of Trichinella larvae in Japanese wild bears remain poorly understood. This study investigated the prevalence of Trichinella spp. in brown bears (Ursus arctos) from Hokkaido, and Japanese black bears (Ursus thibetanus japonicus) from three prefectures (Aomori, Akita, and Iwate) in northern Japan, between April 2019 and August 2022. Trichinella larvae were detected in 2.5% (6/236) of the brown bears and 0.9% (1/117) of the Japanese black bears. Sequence analysis using two genetic loci, the internal transcribed spacer region of nuclear ribosomal DNA and the mitochondrial cytochrome c oxidase subunit I gene, revealed that the larvae collected from the seven infected bears were identical to one of the two haplotypes of Trichinella T9. The prevalence of Trichinella T9 is low but is maintained in bears in the Hokkaido and Iwate prefectures suggesting that undercooked meat from these animals could cause human infection. Thus, continued health education campaigns are needed to raise awareness of the potential risk of trichinellosis among hunters, meat suppliers, consumers, and local governmental health agencies.