Metagonimus yokogawai (Trematoda: Heterophyidae): From Discovery to Designation of a Neotype

Metagonimus yokogawai (Katsurada, 1912) Katsurada, 1912 (Trematoda: Heterophyidae) is parasitic in the small intestine of mammals including man and birds in Far Eastern Russia, Korea, Japan, China, and Taiwan. In the present study, the metacercariae and adults of M. yokogawai were redescribed to designate a neotype of this fluke together with reviews of previous studies including study histories from the first discovery to now. We particularly, attempted to review the study histories and morphological descriptions of M. yokogawai for the species validity, and compared with the morphological characteristics and life cycles of the closely related species, Metagonimus takahashii and Metagonimus miyatai. Finally, we proposed a differential key for the 8 known Metagonimus species distributed in East Asia. Metacercariae were obtained from the body muscles of sweetfish (Plecoglossus altivelis) collected in the Asahi River at Takebe-cho, Kita-ku, Okayama City, Okayama Prefecture, Japan. Adults were recovered from the small intestine of Syrian golden hamsters, to which the metacercariae had been fed 14 days before. A neotype was selected out of the present adult specimens. The Asahi River at Takebo-cho became the type locality of M. yokogawai. In conclusion, the present review shows that M. yokogawai, M. takahashii, and M. miyatai are valid and discriminated by means of morphological characteristics.

Prevalence of heterophyid infection among Japanese residents of Egypt (2005-2008) and its association with length of stay

A total of 300 stool samples collected from 213 Japanese residents of Egypt were examined microscopically. Among these samples, 39 were judged positive for heterophyid eggs. Sixty seven residents were examined repeatedly. The prevalence of heterophyid eggs revealed by the first examination samples was 8.5% (18⁄213) whereas that revealed by the second follow-up was 24% (16⁄67). The interval between the first and second examination was one year in 58 cases and 2 years in 9 cases. <br>The association of infection with the length of stay in Egypt was evident. Positivity among new residents (period of stay in Egypt ‹ 1 year) was as low as 3% (2⁄60). Positive conversion from new residents was observed in 28% (7⁄25), indicating a positive association between heterophyid infection and the length of stay in Egypt among Japanese residents of that country.