The Development of the Endogenous Stages of \u3cem\u3eEimeria ninakohlyakimovae\u3c/em\u3e (Yakimoff and Rastegaieff, 1930) in Domestic Sheep

Forty-five mixed breed lambs, 1 to 4 months of age, were used to study the patent period and endogenous stages in the life cycle of Eimeria ninakohlyakimovae. The lambs were inoculated with oocysts of this species and killed at daily intervals from 1 through 14 days after inoculation. From all lambs of the study sections of intestinal tissue were prepared by routine methods for histological examination. E. ninakohlyakimovaewas observed to have 2 generations of schizonts in its endogenous development. Mature, first-generation schizonts had an average diameter of about 290 μ and had many thousands of merozoites, averaging 11.9 by 2.1 μ. Macroscopically, these schizonts appeared as small white bodies in the mucosa of the ileum, with the largest numbers occurring 5 to 15 feet anterior to the ileocecal valve. Young, first-generation trophozoites, having a crescent body in the parasitophorous vacuole and at least 1 refractile body, were observed as early as 3 days post-inoculation. These underwent development in cells of the lamina propria which were adjacent to the base of the crypts of Lieberkuhn. As the schizonts grew, the adjacent wall of the crypt became indented. The cytoplasm of the host cell harboring the parasite increased in volume, and its nucleus and nucleolus became enlarged. The host cell then became surrounded by an envelope of flattened cells. Within the developing schizonts, the nuclei multiplied, and at about 7 days post-inoculation they became arranged in a single layer at the periphery. By a series of infoldings of this layer, compartments were formed within the schizont. The parasitophorous vacuole appeared to form inpocketings in association with the infoldings. The compartments later gave rise to spheroidal bodies (blastophores) having a single peripheral layer of nuclei. From the blastophores outgrowths occurred; these formed the first-generation merozoites. Mature first-generation schizonts appeared 9 to 10 days post-inoculation. Many mature schizonts became surrounded by leucocytic cells, which later invaded and destroyed the schizonts. Phagocytosis of the merozoites by macrophages in invaded schizonts was observed. Mature, second-generation schizonts developed in epithelial cells lining the crypts in the large intestine 10 to 11 days after inoculation. Development required about 1 to 2 days. When mature, these schizonts averaged about 12 μ in diameter and had an average of 24 merozoites. These merozoites averaged 5.5 μ by 1.4 μ. Many appeared to have a crescent-shaped distribution of chromatin in their nuclei. The merozoites developed in a manner similar to that in individual blastophores of first-generation schizonts. A crescent body was present in second-generation schizonts. At 11 through 14 days post-inoculation, sexual stages were observed in the epithelial cells lining the crypts of Lieberkuhn in the large intestine. Thirty mature microgametocytes averaged 15.0 by 11.6 μ. In mature microgametocytes, the microgametes were arranged peripherally about a central residual mass. Thirty mature macrogametocytes averaged 16.1 by 12.3 μ. Within the nucleus of young macrogametocytes, a basophilic body (satellite body) was observed adjacent to the nucleolus. At maturity, the cytoplasm of the macrogametocytes contained numerous eosinophilic and basophilic granules. A crescent body was present in the parasitophorous vacuole of both macrogametocytes and microgametocytes. Thirty unsporulated oocysts, in situ, averaged 17.6 by 13.3 μ. The prepatent period in 4 lambs was 11 days and the patent period in 2 lambs was 7 days. The pattern of endogenous development of E. ninakohlyakimovae closely resembles that of E. bovis