Survey for Gnathostoma nipponicum Larvae in Gobiid Freshwater Fish and Infectivity of the Larvae to a Gobiid Fish (Chaenogobius urotaenia)

概要

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From June 1993 to November 1996, a total of 977 gobiid fish consisting of three species (Tridentiger brevispinis, Chaenogobius urotaenia, and Rhinogobius brunneus) collected from eastern Aomori Prefecture, were examined for Gnathostoma nipponicum larvae infection. Only one species, C. urotaenia was infected with advanced third-stage larvae (AdL3), and a total of 22 larvae were recovered from 17 (3.4%) of 500 fish. The infected fish were larger than 12 cm in body length and collected in the May-June and September-November seasons. Experimental studies confirmed that C. urotaenia was susceptible to both the early third-stage larvae (EaL3) obtained from Eucyclops serrulatus and AdL3 from Misgurnus anguillicaudatus. Eight of 10 C. urotaenia inoculated orally with 10 EaL3 were positive, and 36 AdL3 were recovered from them (recovery rate: 36.0%) at 30 days postinoculation (PI). All 10 C. urotaenia inoculated with 10 AdL3 were also positive, and a total of 63 AdL3 were recovered (recovery rate: 63.0%) at 10 days PI. The main location of the larvae was the body muscles of the fish. No morphological alterations or death of the larvae were observed in this study. From these results, it seems that the C. urotaenia has characteristics suitable to be the host to the larvae and they may serve as the second intermediate and paratenic host in the natural life cycle of this nematode.