Date of Award:

5-1968

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Animal, Dairy, and Veterinary Sciences

Department name when degree awarded

Zoology

Committee Chair(s)

Datus M. Hammond

Committee

Datus M. Hammond

Committee

Thomas L. Bahler

Committee

Paul B. Carter

Committee

Merthyr L. Miner

Committee

Raymond T. Sanders

Abstract

In a study of the life cycle of Eimeria auburnensis, 51 of 57 Holstein-Friesian calves were used to study endogenous stages, and the remainder to investigate the prepatent and patent periods. In vitro excysted sporozoites of E. auburnensis were introduced into intestinal fistulas in 8 calves and into the intestine via laparotomy in 2 others. One or more of the 51 calves were killed at daily intervals beginning on the second day and continuing until the 19th day after inoculation. The tissues from calves were prepared by routine histological techniques for nicroscopic examination. First-generation asexual endogenous stages were located in epithelial cells at or near the base of the crypts in the ileum and jejunum. Intracellular sporozoites with 2 refractile bodies were much more numerous than those with 1 refractile body. Typically rounded, uninucleate trophozoites were not observed. Many schizonts having a sporozoite shape and 2 to 6 nucleu were observed. Many such sporozoite-shaped schizonts had lateral bulges with one or more nuclei; these apparently transformed directly into typical schizonts. Young schizonts had nuclei which were randomly arranged; later these assumed a peripheral location. Beginning on the 8th day after inoculation, infolding of the peripheral nuclear layer occurred, forming numerous invaginations. Each invagination had a lightly staining lumen, which was continuous with the parasitophorous vacuole; the wall surrounding the lumen had a single layer of closely spaced nuclei. In schizonts approaching maturity, at 9 and 10 days, merozoites were formed by budding from the walls of the invaginations. In mature schizonts, first observed at 10 days after inoculation, the merozoites were randomly distributed. Such schizonts contained many thousands of merozoites and occupied the whole width of the crypt, obliterating the epithelial cells along the sides.

Second-generation schizonts and gametocytes occurred in mesodermally derived cells of the lamina propria, under the epithelium in the upper one-half of the villi. Mature second-generation schizonts, observed in 12-, 14-, and 15-day infections, had 4 to 11 merozoites. A number of host cells harbored gametocytes in addition to the mature second-generation schizonts.

A small amount of glycogen was observed in intracellular sporozoites. This increased in the resulting schizonts, and first-generation merozoites had many granules of glycogen in the middle two-thirds of the body. Second-generation merozoites had less glycogen. All nuclei of asexual stages were Feulgen-positive.

Gametocytes were first seen on the 14th day after inoculation. Macrogametes had large nuclei and nucleoli, and many had a basophilic satellite body near the nucleus. Cytoplasmic granules first appeared at 16 days after inoculation; the oocyst wall began to form at 17 days after inoculation and at 18 and 19 days many fully formed oocysts were seen. Only the youngest macrogametes, seen at 14 days after inoculation, were Feulgen-positive; all others were Feulgen-negative. PAS-positive granules were seen in increasing numbers in macrogametes beginning on the 15th day after inoculation. In oocysts the entire cytoplasm appeared strongly PAS-positive.

Microgametocytes, first seen in 14-day infections, had 2 or more nuclei. During development the nuclei were randomly arranged until microgamete development began. then the nuclei were arranged in rows and at the surface of compartments within the microgametocyte. The microgametes formed in rows at the surface of the compartments, which contained lightly stained residual material. Mature microgametes were arranged in whorls. Mature microgametocytes were seen in abundance in 18- and 19-day infections. Microgametocytes were PAS-negative until the 17th day after inoculation, at which time they were weakly positive. Mature microgametocytes were strongly PAS-positive in areas corresponding to the location of microgametes.

Basophilic crescent-shaped bodies were observed in vacuoles of host cells parasitized by fist-generation schizonts, microgametocytes and macrogametes. These were PAS-negative and Feulgen-negative; their significance is unknown.

In 6 calves, the mean prepatent period for E. auburnensis was 17.5 days, and the patent period averaged 3.3 days.

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