Abomasal coccidiosis associated with proliferative abomasitis in a sheep.

Abomasal coccidiosis was diagnosed in an 11-month-old female sheep that died after a 2-week period of anorexia and diarrhea. The abomasal mucosa was grossly thickened with a nodular surface and focal areas of hemorrhage. Microscopically, the middle to deep abomasal mucosa contained many intact and ruptured giant protozoal schizonts associated with hyperplasia of mucous neck cells, parietal cell atrophy, moderate lymphocytic-plasmacytic inflammation, and fibrosis centered on mineralized remnants of degenerate schizont walls. Sexual tissue stages and oocysts were not present. Microscopic features of schizonts and ultrastuctural features of merozoites were comparable to previous descriptions of Eimeria (Globidium) gilruthi, a coccidian of uncertain taxonomic status historically associated with incidental infections of the abomasum in sheep and goats. The distinctive lesions suggest that, similar to ostertagiasis, heavy coccidial infection of the abomasum should be considered as a cause of anorexia, diarrhea, and proliferative abomasitis in sheep.