MIGRATION AND DEVELOPMENT OF THE LARVAE OF GNATHOSTOMA-NIPPONICUM IN THE RAT, 2ND INTERMEDIATE OR PARATENIC HOST, AND THE WEASEL, DEFINITIVE HOST

Migration and development of the larvae of Gnathostoma nipponicum in t he rat as second intermediate or paratenic host and the weasel as defi nitive host were examined to clarify the pathogenesis in each animal. The advanced third-stage larvae (AdL3) given orally to rats remained i n the stomach for 12 h post-infection (PI). After that, larvae transie ntly invaded various organs and finally moved into the muscle within 4 8 h. The percentage of eosinophils in the blood taken from the jugular vein of rats infected with AdL3 reached a maximum (about 6%) on day 2 0 PI and then decreased. IgG antibody titre for G. nipponicum measured by ELISA began to increase on day 5 PI and reached a plateau on day 2 0 PI. The AdL3 given orally to weasels moved from the stomach into the muscle and then increased in size. Half of them invaded the muscle wi thin 5 days, whereas the majority of them invaded the muscles within 2 0 days PI. Morphology of worms which invaded the muscles indicated tha t they were still the larval form with three rows of hooklets on the h ead bulb. The larvae in the muscles developed to young adult worms wit h seven rows of hooklets on the head bulb within 40 days Pl. These you ng adult worms invaded the oesophageal wall and formed a tumour within 60 days Pl. It was presumed that worms invaded the oesophageal wall t hough the adventitia. Ferret and mink were shown to be potential final hosts of G. nipponicum.