Scanning electron microscopy of damage to the cecal mucosae of chickens infected with Eimeria tenella.

A group of chickens were inoculated with 100,000 Eimeria tenella oocysts each. The birds were sacrificed on days 4-14 postinoculation. Tissue samples from 4 different areas of each cecum examined were obtained and processed by the osmium-thiocarbohydrazide-osmium technique. Examination of the prepared tissues with the scanning electron microscope revealed lesions ranging from localized tissue swelling to complete disruption of the mucosal epithelium due to the rupture of large numbers of epithelial cells. The amount of damage to the tissue varied greatly, tending to be most obvious in the 2 more distal regions of the ceca examined. Observed in addition to the pathological changes demonstrated were some specific stages of the parasite, including schizonts, merozoites, and oocysts.