Case Study of Human Infection with a Marine Species Diphyllobothriid Tapeworm: Morphological Variations of Strobila due to Fixation Procedures
A case of human infection with a marine species diphyllobothriid found in Hiroshima Prefecture, Japan is reported. The infected patient was a 49-year-old man living in Fukuyama City, Hiroshima Prefecture, Japan. On July 4th, 1994, the patient had spontaneously discharged a diphyllobothriid strobila with no scolex about 50 cm in length and 22 mm in maximum width. After the treatment with praziquantel on November 12th, 1994, the patient had discharged again a remaining strobila without scolex of 85 cm in length and 21 mm in maximum width. Morphological characteristics of the strobila and eggs were as follows. 1) Segments 3.5 to 4.0 mm in length, 22 mm in maximum width and 0.7 mm in thickness. 2) Single set of reproductive organs per segment. 3) Uterus with 6 to 8 loops on each side, not much extended laterally. 4) Single layer testes about 2000 testes per segment. 5) Very prominent genital papillae. 6) Pyriform cirrus-sac oblique and thick-walled seminal vesicle connected dorso-caudally in sagittal section. 7) Eggs 72.4 μm by 54.1 μm in average and egg-shells with scattered pits on the surface. From these findings, the strobila in the present case was identified as of Diphyllobothrium yonagoense Yamane et al, 1981. To our best knowledge, the present report deals with 15th finding of human infection with D. yonagoense in Japan. Morphological variations of the strobila due to the fixation procedures are also discussed.