Lethality of intestinal tissue extracts from Eimeria-infected chickens

Evidence exists that lethal activity is associated with extracts from Eimeria tenella-infected caecal tissues. We examined tissues of the small intestine infected with other species of Eimeria for a similar lethal activity. Extracts were prepared from intestinal tissues of chickens infected with either E. acervulina, E. brunetti, E. maxima, E. mitis or E. necatrix. Appropriate control extracts from tissues of non-infected chickens were also prepared. Intravenous injection of the extracts into healthy chickens showed that lethality of infected tissue extracts was higher than control extracts and was independent of the site of infection within the intestine. Comparison of the lethality of caecal extracts from chickens infected with embryo-adapted or parent lines of E. tenella showed that lethality was independent of the recognized pathogenic characteristics of the lines. Also, it was demonstrated that lethal activity is associated with extracts of tissues containing massive numbers of arrested and non-arrested sporozoites and early trophozoites.