Behavior of invasive stages of Eimeria tenella in the immune fowl ( Gallus domesticus)

Abstract

Although sporozoites readily invaded the cecal epithelium of fowls resistant to Eimeria tenella, they did not develop further and subsequently were not detected in tissue sections after the 72nd hour of infection. Sporozoites harvested from the cecal lumen of an immune fowl produced infections in suceptible fowls equivalent to those produced by similar numbers of sporozoites from the ceca of a nonimmune fowl. Similarly, second generation merozoites inoculated, per rectum or directly, into the ceca of immune fowls invaded the cecal tissue and reached the expected site of development but failed to grow and were not detectable 30 hours after infection; very few or no oocysts were recovered. This suggests that immune mechanisms are not directed against the parasite within the lumen of the cecum or during the initial migratory phases and are only effective after the sporozoite or merozoite has penetrated the cecal mucosa and migrated to the intracellular site normally associated with the further development of the life cycle.