Life Cycles of Three Species of Eimeria from the Uinta Ground Squirrel, Spermophilus Armatus

Life Cycles of Three Species of~ from the Uinta Grou nd Squirrel, Spermophilus ~ by Kenneth S. Todd, Jr . , Doctor of Philosophy Utah State University, 1967 Major Professor: Dr. Datus M. Hammond Department: Zoo logy A study of the coccidia of the Uinta ground squirre l, Spermophilus (C itellus) armatus , was undertaken to determine the incidence of coccidia in a popu l ation of these ground squirrels , the life cycle and pathogenicity of the coccidia , and the host specificity of certain of the species of coccidia found in this and five other spec i es of grou nd squirr e l s ~richardsoni, ~· var i ega tus, ~· l atera lis, ~ · columbianus, and~ · beecheyi). Uinta ground squirrels were live trapped and their feces examined to determine the incidence of coccidian infection. Specimens of ~· ~ were maintained in the laboratory and given a pure inocu lum of~ callospermophili, ! · l ar imere ns is, or~bilamellata. The animals were then killed at 12 to 24 hour intervals, and tissues were prepared by routine histological methods for microscopical examination. Oocysts of these three species of coccidia from other species of ground squi rre l s caused patent infections in S. armatus. Spermophilus richardsoni co~ Ld not be infected with ! · Larimerensis or E. bilamellata . The incid ence of infection in each of the three species of coccidia was similar in adult and juvenile animals. Eime ria bilame llata had the Lowest incidence of the three species, and was the only one that caused immunity or was pathogenic in experimental infections. ~ callos permophili was recovered from five of the six species of ground squ irrels examined and f rom the p r air i e dog, Cy nomys l eucurus. This is evidently the first time that a species of ~ has been found in two rodent genera. ~ l arimerensis, a species prev iously reported from prairie dogs, was found in~· armatus . Endogenous s t ages of~ · callospermophili were located above the host ce ll nuclei of epithe l ial ce lls on t he villi of the sma ll i ntestine . 1wo asexual stages preceded the sexual. stages, and oocysts were first discharged five days after inoculation. The life cycle of~· l arimerensis was similar to that of~· ca llos permophili, ex cept that greater numbers of merozoi t es were produced during schizogony and the e nd oge nous stages were located below the host cel l nuclei. Developing macrogametes of these two species differed i n that those of ! · callospermophili cont ained basophi lic plastic granules that l ater ass umed eosinophi lic properties. The pl as tic gra nules of! · larimerensis were eosinophilic throughout the development of the macrogametes. Mi crogametocytes of ! · ca llos permophili had a simp l e type of deve lopment, in which the microgametes we r e formed around the periphery of the game t ocyte; the microgametes of ~· Larimerensis developed around internal formative areas of the gametocyte as well as peripherally . The asexua l development of~· bilamellata was determined on l y in part. Matu r e schizont s were present on the seventh day after inoculation, and gametogenesis began at t his time; oocysts were first di scharged on the tenth day after inoculation. Eimeria bi l ame llata differed from the other two spec i es in that gametocytes developed in epithe lia l ce lls, which became displaced, f inal l y being located deep in the Lamina propria of the mucosa. Macrogametes conta ined both basophil ic a nd eosinophilic plastic gra nules . Microgametogony was more complex tha n in the other two species, and the microgame t ocy tes were much l arger , producing thousand s of game t es. Excysted sporozoites of the three species of coccidia differed in morphology and s t aining properties. The s porozoites of~· ca llos pe rmophili and ~· l ar i merensis had unusually l a r ge posterior refractile bodies. Eimeria cal l ospermophili was also unusual i n t hat no PAS positive materia l was found in the sporozoites.