Human infection by a “fish tapeworm”, Diphyllobothrium latum, in a non-endemic country

We document a case of locally acquired “broad- or fish-tapeworm” infection caused by Diphyllobothrium latum in a 27-year-old Spanish man, confirmed by molecular analysis (COI gene). The patient had naturally expelled a worm of 110 cm in length, but the physical examination did not yield any remarkable findings, and the patient did not suffer from any particular symptoms. Laboratory test results were normal except for a remarkable increase in the red blood cell count, and an evident decrease in the mean corpuscular volume and mean corpuscular hemoglobin. Vitamin B₁₂ and folic acid values were in the normal range without signs of anemia. It was suggested that these anomalies in erythrocyte formation might not be related to the parasite, and analysis of the patient’s anamnestic data revealed that the infection could only have been caused by the ingestion of imported fish, although no light could be shed on the specific source of infection. From a public health viewpoint, this human case of fish-borne zoonosis is exemplary, suggesting that not only is control of fish and fish product quality essential, but also increased awareness of the general population with regard to changes in culinary habits.