An egg-adapted (attenuated) line of Eimeria necatrix: further studies on its reproduction, pathogenicity and immunogenicity

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Abstract
SUMMARY: An egg-adapted line of Eimeria necatrix has now been passaged 40 times in the chorio-allantoic membranes of embryonated eggs. Between the 21st and 40th passage in eggs the parasite was subjected to a selection for precocious development, and its pre-patent period in this host is now 123–125 h. The parasite continued to adapt to the chorio-allantoie this tissue caused the growth of the host embryo to be markedly stunted. In chickens, both the reproduction and the pathogenicity of the egg-adapted line decreased with increasing numbers of passages in eggs. A comparison of teh immunogenicity of te egg-adapted line and its parent strain in chickens kept on litter, showed that substantially more oocysts of the egg-adapted line had to be given to induce complete protection.