Incubation in rats of a nematodal larva from cod to establish its specific identity: Contracaecum osculatum, (Rudolphi).

Infective, third-stage larvae of the genus Contracaecum from fish were cultured in vitro and fed to laboratory animals in order to obtain later developmental stages to permit their specific identification. The in vitro incubation was unsuccessful. In orally infected laboratory rats and hamsters, fourth-stage larvae were obtained from the stomach at 2-5 days postinfection (p.i.), but no adult worms developed. Larvae introduced surgically into the body cavity of laboratory rats yielded some adult worms from day 42 onwards. Adult males were identified as Contracaecum osculatum.