Dietary footprints of a global parasite: diagnosing Dibothriocephalus nihonkaiensis in non-endemic regions

Species within the genus Dibothriocephalus/Diphyllobothrium are notable for being among the largest cestodes capable of human infection. Historically, Dibothriocephalus latus (previously Diphyllobothrium latus) is considered the more prevalent species (in Europe and Patagonia). However, Dibothriocephalus nihonkaiensis (previously Diphyllobothrium nihonkaiensis) is commonly found in East Asian countries, particularly Japan, where diets frequently include raw salmons. The increasing globalization and adoption of diverse dietary practices have led to the detection of tapeworm infections like D. nihonkaiensis outside their traditionally endemic areas, potentially making them more common than previously thought, as exemplified by the present case in Singapore. A 35-year-old Chinese female presented with chronic abdominal distension, loose stools and unintentional weight loss. 3 months prior to her symptom onset, she had travelled extensively throughout Asia (Thailand, Vietnam, Laos, Malaysia and China) and Mexico and had consumed raw salmon throughout her travels. A full blood count revealed eosinophilia, and a worm was passed during bowel preparation. Molecular sequencing identified it as D. nihonkaiensis. She was treated successfully with praziquantel. Increased globalization, cross-cultural dietary exchange, and greater salmon consumption have expanded the geographic distribution of D. nihonkaiensis infections beyond previously endemic regions. Consequently, clinicians worldwide must maintain a high index of suspicion for this parasitic infection, even in non-endemic areas. A thorough patient history, with particular attention to dietary habits and travel, is paramount for accurate and timely diagnosis, thereby enabling appropriate treatment and preventing potential complications. Increased awareness, reporting, and molecular identification of Dibothriocephalus are crucial for determining infection sources and guiding food safety surveillance.