David J. Doran

The life cycle of Eimeria dispersa Tyzzer 1929 from the turkey in gallinaceous birds.

The life cycle of a turkey strain of Eimeria dispersa was studied in chickens, Chukar partridge, Ring-necked pheasant, and Bobwhite quail. Endogenous development in partridge and quail differed from development in chickens and pheasant. In partridge and quail, mature 1st-, 2nd-, and 3rd-generation schizonts, macrogamets, and oocysts were found in tissue sections at an earlier time interval, mature 1st-generation schizonts were larger, and mature 1st-, 2nd-, and 3rd-generation schizonts contained a greater number of merozoites that were longer. The only apparent similarity among the 4 hosts was the size of mature 2nd- and 3rd-generation schizonts. The life cycle was completed in all 4 species of birds. The prepatent period was approximately 6 hr shorter in partridge and quail than in chickens and pheasant. Two partridge and 2 quail given 50,000 sporulated oocysts each shed a total of 23 million and 135 million oocysts, respectively, during 4-day interval. Two chickens and 2 pheasant given the same dosage shed a total of only 70,000 and 1 million oocysts, respectively, during the same interval. Oocysts from partridge and quail sporulated more quickly and were slightly larger than those from chickens and pheasant.

Ultrastructure of Cytoplasmic and Nuclear Changes in Eimeria tenella during First-Generation Schizogony in Cell Culture

Eimeria tenella sporozoites were inoculated into primary cultures of chick kidney cells. Cells fixed from 1 1/2 to 54 hr later were examined with the electron microscope. At 1 1/2 and 24 hr, most intracellular sporozoites were fusiform and retained organelles typical of extracellular sporozoites. However, at 35 hr, rounded trophozoites were present without these structures; only a refractile body, nucleus, mitochondria, and endoplasmic reticulum remained. Binucleate parasites were also present at that time, but at 48 hr many multinucleate schizonts were present. Nuclei, with adjacent conoids, were at the periphery of these schizonts. Partly developed merozoites, each containing a conoid and a nucleus, protruded into the parasitophorous vacuole. At 54 hr, fully developed merozoites were separated from the residual body. Merozoites resembled sporozoites but lacked the large refractile bodies seen in sporozoites. Linear inclusions were present near the merozoite nucleus and in the residual body. Round vacuoles and ribosomes were also found in the residuum. Nucleoli were first seen in sporozoite nuclei at 1 1/2 hr. They were also present in merozoites but were more prominent in trophozoites and schizonts. Peripheral and scattered nuclear heterochromatins were prominent in intracellular sporozoites and diminished in trophozoites, but increased after several nuclear divisions and were again prominent in the merozoite. Small, distinct interchromatin granules were found in all stages. Intranuclear spindles, centrocones, and centrioles were found in connection with nuclear divisions. Ultrastructure of first-generation schizogony in cell culture was similar to that described for second-generation E. tenella in the chicken and to schizogony of other species of Eimeria.