Diphyllobothrium nihonkaiense detected in a mother and daughter
Diphyllobothrium nihonkaiense and Diphyllobothrium latum are tapeworms that parasitize various mammals, including humans. These tapeworms can infect humans and cause a condition known as diphyllobothriasis. Both Diphyllobothrium species are morphologically similar, making differentiation difficult without parasitological expertise. In Japan, 80%-90% of cases of diphyllobothriasis are caused by D. nihonkaiense . However, owing to the globalization of food culture and habits, individuals have an increased opportunity to consume raw fish imported from abroad, including from Europe. To differentiate Diphyllobothrium species, molecular techniques such as DNA sequencing of the 18S rRNA gene have been introduced. DNA Sequencing of the mitochondrial cytochrome c oxidase subunit I (cox1 ) gene is commonly used to identify Diphyllobothrium species.The cox1 gene homology enables identifying the Diphyllobothrium species. Here, we diagnosed cases of diphyllobothriasis in a mother and daughter as sequential cases. We report two cases of D. nihonkaiense infection in a mother and her daughter. The daughter (case 1), who noticed the passage of worms during defecation without experiencing abdominal symptoms, was the index case. She visited our hospital with her mother, bringing the tapeworm. Microscopic examination of the segmented proglottides morphologically identified the tapeworm as D. nihonkaiense . The daughter underwent no further examinations, including venipuncture or gastrointestinal examinations. The tapeworm was temporarily stored in saline solution and later preserved in 80% alcohol. The mother (case 2) complained of abdominal pain, diarrhea, and worm excretion. She had excreted tapeworms the previous week and had visited another hospital, where she was scheduled to be referred to our hospital. The mother was examined via Gastrografin® at the initial hospital, and her tapeworm samples were preserved in formalin. Molecular analysis of the mitochondrial cox1 gene confirmed that both tapeworms were D. nihonkaiense . We considered this diphyllobothriasis to be coincidental in the same family, although no source of infection was identified. No scolex was found in the excreted samples from either patient. After follow-up of the family, no recurrence or new diphyllobothriasis were observed. In both cases, two D. nihonkaiense tapeworms were found within the same period. The causative tapeworms were brought to the department of laboratory medicine in our institute, with one preserved in 80% alcohol and the other fixed in formalin. Before preservation or fixation, morphological examinations were performed, diagnosing the tapeworms as D. nihonkaiense . This diagnosis was tentative but reasonable given the high prevalence of D. nihonkaiense in Japan. Owing to shrinkage of the tapeworm sample from the mother, inspection was challenging. DNA typing is a confirmatory method for accurately diagnosing diphyllobothriasis. In our cases, molecular detection was effective in confirming differentiation of both worms. However, molecular methods require several days to confirm results, highlighting the need for laboratory technicians to develop expertise in parasitology.
