Try to read :
Bolek M. G., 1997 : Seasonal occurrence of Cosmocercoides dukae and prey analysis in the blue-spotted salamander, Ambystoma laterale, in southeastern Wisconsin - J. Helminthol. Soc. Wash., 64 (2): 292-295
and
Vanderburgh D. J. & Anderson R. C., 1987 : The relationship between nematodes of the genus Cosmocercoides Wilkie, 1930 (Nematoda: Cosmocercoidea) in toads (Bufo americanus) and slugs (Deroceras laeve) - Canadian Journal of Zoology 65(7)