The incidence of human diphyllobothriasis is expected to rise amidst the current global popularity of Japanese cuisine, such as sushi, which contains raw fish. We report a case of a 10-year-old boy with a diphyllobothriasis infection acquired via sushi consumption. The patient was otherwise healthy, exhibited no symptoms, and was successfully treated with a single dose of 10 mg/kg praziquantel. In Japan, this parasite is known as \"Sanada-mushi\" because it resembles a Sanada cord. Prompt recognition of this parasite by evoking the Sanada cord\'s appearance may facilitate early diagnosis and treatment and increase public awareness to prevent diphyllobothriasis.

A 72-year-old man with ileocecal lymphadenopathy was found to have Epstein-Barr virus-positive diffuse large B-cell lymphoma using open biopsy, and an ileostoma was created. R-CHOP-like chemotherapy was initiated, but his malnutrition did not improve. After 3 cycles of chemotherapy, a 2-m-long Cestoda was removed from the stoma and was identified as Diphyllobothrium nihonkaiense using mitochondria cytochrome c oxidase subunit 1 targeted polymerase chain reaction analysis. Although D. nihonkaiense infections are asymptomatic, the ileostomy was thought to have exacerbated the malabsorption in this patient. Parasitic infections are rare; however, they should be added to the differential diagnosis of malnutrition of unknown cause during chemotherapy for hematological malignancies.

A 6-year-old girl was admitted to our hospital due to discharging the strobila of a tapeworm (Diphyllobothrium nihonkaiense) from her anus. Before excreting the tapeworm completely with anthelmintics, ultrasonography was performed. The tapeworm was shown as a slightly high echoic strand-like lesion on ultrasonography in the terminal ileum. In this strand-like lesion, some high echoic spots were detected. This finding was considered as a characteristic of Diphylloborthriasis.

We report 958 cases of cestodiasis occurring in Japan during 2001-2016. The predominant pathogen was Diphyllobothrium nihonkaiense tapeworm (n = 825), which caused 86.1% of all cases. The other cestode species involved were Taenia spp. (10.3%), Diplogonoporus balaenopterae (3.3%), and Spirometra spp. (0.2%). We estimated D. nihonkaiense diphyllobothriasis incidence as 52 cases/year. We observed a predominance of cases during March-July, coinciding with the cherry salmon and immature chum salmon fishing season, but cases were present year-round, suggesting that other fish could be involved in transmission to humans. Because of increased salmon trade, increased tourism in Japan, and lack of awareness of the risks associated with eating raw fish, cases of D. nihonkaiense diphyllobothriasis are expected to rise. Therefore, information regarding these concerning parasitic infections and warnings of the potential risks associated with these infections must be disseminated to consumers, food producers, restaurant owners, physicians, and travelers.

We described 4 human infection cases of zoonotic fish-tapeworm, Diphyllobothrium nihonkaiense, identified with morphological and molecular characters and briefly reviewed Chinese cases in consideration of it as an emerging parasitic disease in China. The scolex and mature and gravid proglottids of some cases were seen, a rosette-shaped uterus was observed in the middle of the mature and gravid proglottids, and the diphyllobothriid eggs were yellowish-brown in color and displayed a small knob or abopercular protuberance on the opposite end of a lid-like opening. The average size of the eggs was recorded as 62-67×42-45 μm. The parasitic materials gathered from 4 human cases were morphologically identified as belonging to the genera Diphyllobothrium and Adenocephalus. The phylogenetic analysis based on the nucleotide sequences of cytochrome c oxidase subunit 1 gene of the etiologic agents confirmed that the 4 cases were D. nihonkaiense infection. The finding of 4 additional D. nihonkaiense cases suggests that D. nihonkaiense might be a major causative species of human diphyllobothriasis in China. A combined morphological and molecular analysis is the main method to confirm D. nihonkaiense infection.

Diphyllobothriosis is reemerging because of global importation and increased popularity of eating raw fish. We detected Diphyllobothrium nihonkaiense plerocercoids in the musculature of wild pink salmon (Oncorhynchus gorbuscha) from Alaska, USA. Therefore, salmon from the American and Asian Pacific coasts and elsewhere pose potential dangers for persons who eat these fish raw.

Human diphyllobothriasis is a widespread fish-borne zoonosis caused by the infection with broad tapeworms belonging to the genus Diphyllobothrium. In mainland China, so far 20 human cases of Diphyllobothrium infections have been reported, and the etiologic species were identified as D. latum and D. nihonkaiense based on morphological characteristics or molecular analysis. In the present study, proglottids of diphyllobothriid tapeworms from 3 human cases that occurred in Heilongjiang Province, China were identified as D. nihonkaiense by sequencing mitochondrial cytochrome c oxidase subunit I (cox1) and NADH dehydrogenase subunit 5 (nad5) genes. Two different cox1 gene sequences were obtained. One sequence showed 100% homology with those from humans in Japan. The remaining cox1 gene sequence and 2 different nad5 gene sequences obtained were not described previously, and might reflect endemic genetic characterizations. D. nihonkaiense might also be a major causative species of human diphyllobothriasis in China. Meanwhile, the finding of the first pediatric case of D. nihonkaiense infection in China suggests that infants infected with D. nihonkaiense should not be ignored.

Diphyllobothrium latum and Diphyllobothrium nihonkaiense are morphologically similar to each other, and only genetic method can differentiate clearly between the 2 species. A strobila of diphyllobothriid tapeworm discharged from a 7-year-old boy was analyzed to identify the species by mitochondrial cytochrome c oxidase subunit 1 (cox1) gene sequencing. He and his family (total 4 persons) ate slices of 3 kinds of raw fish 16 days before visiting our outpatient clinic. All family members complained of abdominal pain and watery diarrhea. They all expelled tapeworm strobilae in their stools. They were treated with a single oral dose of praziquantel and then complained of no more symptoms. The cox1 gene sequencing of the strobila from the boy revealed 99.9% (687/688 bp) similarity with D. nihonkaiense and only 93.2% (641/688 bp) similarity with D. latum. Thus, we assigned this tapeworm as D. nihonkaiense. This is the first report of D. nihonkaiense infection in a family in Korea, and this report includes the 8th pediatric case in Korea. The current report is meaningful because D. nihonkaiense infection within a family is rare.

Most of the diphyllobothriid tapeworms isolated from human samples in the Republic of Korea (= Korea) have been identified as Diphyllobothrium nihonkaiense by genetic analysis. This paper reports confirmation of D. nihonkaiense infections in 4 additional human samples obtained between 1995 and 2014, which were analyzed at the Department of Parasitology, Hallym University College of Medicine, Korea. Analysis of the mitochondrial cytochrome c oxidase 1 (cox1) gene revealed a 98.5-99.5% similarity with a reference D. nihonkaiense sequence in GenBank. The present report adds 4 cases of D. nihonkaiense infections to the literature, indicating that the dominant diphyllobothriid tapeworm species in Korea is D. nihonkaiense but not D. latum.

Infection cases of diphyllobothriid tapeworms are not much in the below teen-age group. We report a case of Diphyllobothrium nihonkaiense infection in a 13-year-old boy. He presented with severe fatigue, occasional abdominal pain at night time. He also had several episodes of tapeworm segment discharge in his stools. By his past history, he had frequently eaten raw fish including salmon and trout with his families. Numerous eggs of diphyllobothriid tapeworm were detected in the fecal examination. We introduced amidotrizoic acid as a cathartic agent through nasogastroduodenal tube and let nearly whole length (4.75 m) of D. nihonkaiense be excreted through his anus. After a single dose of praziquantel, the child\'s stool showed no further eggs, and his symptoms disappeared. The evacuated worm was identified as D. nihonkaiense by mitochondrial cox1 gene analysis. Here we report a successful extracorporeal worm extraction from an infection case of D. nihonkaiense by the injection of amidotrizoic acid.