Eimeria tenella: Reproduction, pathogenicity and immunogenicity of a strain maintained in chick embryos by serial passage

Abstract

Techniques were developed for the recovery and sporulation of oocysts from embryos, and a strain of Eimeria tenella was successfully passaged through 42 batches of embryos. This was done after the poor yields of oocysts at the 5th and 9th passage had been built up by passaging the strain in groups of chickens. After 28 embryo passages the strain appeared to have a slightly lower pathogenicity for embryos and perhaps also to chickens, but after 37 to 42 passages it was substantially less pathogenic for both chickens and embryos without a corresponding loss of immunogenicity for chickens. Pathogenicity appeared to be largely regained during the second passage of the “adapted” strain in chickens.