Abstract
A strobila of diphyllobothriid tapeworm without secolex (28 cm long and 7 mm wide) was spontaneously evacuated from a 13-year-old female living in Kurayoshi, Okayama Prefecture on November 10, 1993. Morphological characteristics of the strobila and the eggs were as follows. 1) The eggs hatched out both in artificial sea water (Aquamarin ) and in tap water, and embryonation was also observed in physiological saline. 2) The eggs were ellipsoidal with small knobs at opposite site of operculum, measuring 63.9 micro-m length and 45.1 micro-m width in average, and an eggshell was about 1.3 micro-m thick, lacking scattered pits on the surface. 3) The proglottids were wider, measuring 2.1 to 3.0 mm in length and 1.0 mm in thickness, with a length/width ration of 1: 2.7. 4) The genital opining was situated about 1/56 posterior from anterior margin of the proglottid, and prominent papillae existed around the genital opening. 5) The number of the uterine loops was 5 to 7 on each side, not quite elongated laterally, and the most anterior margin of the cirrus-sac. 6) The testis were arranged in a single layer, and there was a distinct boundary between neighboring proglottids. 7) The pyriform cirrus-sac in genital section was situated obliquely in the proglottid, and a subspherical seminal vesicle was connected dorso-caudally to the cirrus-sac, which could be seen from ventral surface of the proglottid. From these findings, the strobila in the present case was identified as Diphyllobothrium latum (Linnaeus, 1758) Luhe, 1910 by Rausch and Hilliard (1970). The patient had eaten raw salmon meat on August 5, 1993, although there was no identification where the salmon had been taken. Recently Yamane et al. (1986, 1994) proposed new theory that so-called broad tapeworm which had so far been classified as D. latum in Japan differed taxonomically from the original D. latum found in northern Europe. Hence the nomenclature of the Japanese broad tapeworm should be altered to D. nihonkaiense. It is the same time supposed that there still exists considerable number of cases of D. latum infection among human diphyllobothriasis in Japan.
Key words: human diphyllobothriasis; salmon; D. latum; broad tapeworm, Cestoda