New observations on first-generation merogony of Eimeria tuskegeensis in Sigmodon hispidus

First-generation development of Eimeria tuskegeensis was evaluated using light microscopy. Sporozoite-shaped meronts containing a prominent refractile body were observed in small intestinal cells of an experimentally infected cotton rat at 24 h post inoculation (PI). Mature spherical or subspherical meronts containing crescent-shaped merozoites were observed at 36 h PI. Refractile bodies were observed in some of these merozoites. Sporozoite-shaped meronts that were isolated from host intestinal cells and inoculated onto human fetal lung cell cultures penetrated the cultured cells by 2 h PI. A mature, subspherical, first-generation meront containing seven merozoites was observed at 9 h PI in cell culture, indicating that sporozoite-shaped meronts isolated from the host retained their infectivity.