Identification of larval Gnathostoma obtained from imported Chinese loaches.

We observed the morphological characteristics and identified the species of gnathostome larvae obtained from the imported Chinese loaches. The early third-stage larvae (EL3) were collected from viscera of the loaches and a part of them were infected to mice. The advanced third-stage larvae [AdL3] were recovered from the mice at 4 weeks post-infection, both larval worms were fixed with 10% formalin, cleared in alcohol-glycerin solution, mounted with glycerin-jelly, and observed. A total of 369 EL3 were collected from viscera of 9,493 Chinese loaches. The whole body of EL3 was covered with about 190 transverse rows of minute cuticular spines and 0.624 x 0.101 mm in average size. A pair of lips were protruded at the anterior end, and the muscular esophagus and brownish intestine were followed. The characteristic head bulb was provided with 4 rows of hooklets. The average number of hooklets in the respective row was 36.7, 39.5, 41.6 and 44.3 posteriorly. AdL3 was 2.660 x 0.346 mm in average size, and retained the esophagus (about 0.755 mm length) and cervical sac (about 0.355 mm length). The average number of hooklets in the respective row on the head bulb was 39.0, 41.9, 43.9 and 45.6, posteriorly. On the basis of the morphological characteristics, they were identified as the third-stage larvae of Gnathostoma hispidum.