Bacteria-Free Cultivation of Some Parasitic Stages of the Swine Nematodes Hyostrongylus rubidus and Oesophagostomum quadrispinulatum (O. longicaudum)

Abstract

Bacteria-free, in vitro cultivation of parasitic stages of the two worms was obtained in a cell-free medium containing a nutrient broth supplemented with sheep serum and acidified aqueous extracts of pig liver and rabbit embryo. The extracts were prepared by the process of "mild extraction". The exceptional clarity of this medium permitted direct microscopic viewing of the larvae within the cultural vessel. Within 42 days at 38.5[degree]C, third stage infective larvae of H. rubidus reached the fourth molt, while those of O. quadrispinulatum reached the fourth stage. Stunting was noted in all stages of H. rubidus beginning with the third molt, and was likewise noted in the fourth stage of O. quadrispinulatum. In the majority of H. rubidus larvae, differentiation of the genital primordium failed to keep pace with somatic differentiation. A lack of information on in vivo development in O. quadrispinulatum precluded a similar comparison.