Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Datus M. Hammond


A total of 176 kangaroo rats (151 Dipodontys ordii and 25 Q• microps) were captured in northwestern utah and examined for coccidia. Of these 176 rats, four Q• ordii (2.6%) and four Q• microps (16.0%) were infected with ~ utahensis, a new species of coccidia. Little seasonal difference was found in the infection rate of either species. The characteristics of the sporulated oocysts of this species were described. A sporocyst plug was reported for the first time in an eimerian oocyst.

Artificially excysted sporozoites were studied by various methods. Thirty living sporozoites averaged 22.5 p in length by 4.5 f in width at the anterior refractile body and 4.6 p in width at the posterior refractile body. The refractile body was ellipsoidal and occupied almost half of the sporozoite. The refractile bodies were protein in nature. Living sporozoites exhibited gliding, flexing, pivoting, and probing movements. Subpellicular fibrils, anterior median rod-shaped organelles, and transverse striations of unknown significance were seen in living and stained sporozoites. In the vesicular nucleus the DNA was concentrated at the periphery and three to five chromatin clumps were present. Little, or no, glycogen was present. The test for lipids was inconclusive.

The mean prepatent period in experimentally infected D• ordii was 9.8 days. The discharge of oocysts continued for prolonged periods, evidently as a result of reinfection, although concerted efforts were made to prevent this.

The asexual endogenous stages were located in epithelial cells in the distal half of the villi of the small intestine. Four generations of schizonts were present. Mature first-generation schizonts were found 2 1/2 days after inoculation of the animals and contained 12 to 16 merozoites. Mature second-generation schizonts were found on the fourth post-inoculation day and also contained 12 to 16 merozoites. Mature t hirdgeneration schizonts were present on the fourth, fifth and sixth postinoculation days and contained 4 to 8 merozoites. The third-generation schizonts gave rise to early sexual stages or to fourth-generation schizonts. Mature fourth-generation schizonts were found on the sixth and seventh post-inoculation days and contained 16 to 24 merozoites.

Young gametocytes were first observed on the fifth post-inoculation day. Shortly after the gametocytes entered the infected epithelial cells the cells became displaced into the lamina propria and the mature gametocytes were usually found in the latter location. The nuclei of infected host cells became considerably enlarged and modified in shape and position. In many host cells there appeared to be two or more nuclei in the parasitized cell; this was interpreted as an artifact of sectioning. However, in a few instances young gametocytes were observed in cells in which the host cell nuclei were undergoing division, indicating that some infected host cells might have been multinucleate.

Microgametocyte nuclei were randomly arranged in the microgametocyte during the early stages of development. As the microgametocytes approached maturity the nuclei became arranged in whorls at the surface of compartments. At maturity the microgametes lost their whorl arrangement and became randomly arranged around a central mass of residual material. The mature microgametocytes averaged 63 .9 by 48.3 p•

The plastic granules of the macrogametes were slightly eosinophilic with hematoxylin and eosin stain, but did not stain with iron hematoxylin. The macrogametes measured 32 .5 by 27 .0 p at the stage in which the plastic granules were at the periphery of the parasite but had not yet coalesced.

Eimeria utahensis caused no outward signs of coccidiosis in experimentally infected D• ordii, nor were any marked pathological changes observed in the tissue sections .

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