Date of Award:

5-1-1971

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Zoology

Committee Chair(s)

Datus M. Hammond

Committee

Datus M. Hammond

Committee

Thomas L. Bahler

Committee

LeGrande C. Ellis

Committee

Paul B. Carter

Committee

Keith L. Dixon

Abstract

Uinta ground squirrels were captured and kept in wire cages in the laboratory. Each of 111 of these squirrels was inoculated during periods from August through November, 1967 to 1969, with 40,000 or 100,000 to 1,000,000 sporulated oocysts of Eimeria bilamellata, E. larimerensis, or E. callospermophili, before or after being placed, without food and water, into a chamber maintained at 7 C. Only juvenile hibernators were used in trials with E. bilamellata and E. larimerensis whereas adults and juveniles were used in trials with E. callospermophili. Each of 121 juvenile and adult squirrels was inoculated with 40,000 sporulated oocysts of one of the three species and kept, with food and water ad libitum, at room temperature (22 C); some squirrels were reinoculated. The squirrels kept at 7 C had periods of torpor interrupted by periods of activity each lasting less than 24 hours. The periods of torpor, during which the rectal temperature was 8 to 10 C, had an average duration of 4, 6, 9, 10, 10, 10, 9, and 6 days respectively, for the months from September through April. Infected room-active squirrels had rectal temperatures of 35 to 38 C. The total amount of feces discharged by the hibernators was 1 to 2 percent of that discharged by room-active squirrels. Of the squirrels kept at 7 C which survived the hibernating period, thirty-four became torpid 1 to 3 days (pretorpid interval) and twenty-six, 4 or more days after inoculation. Inoculum oocysts were observed in the feces of the former group of hibernators for 5 to 239 (mean, 133) days and in the latter group for 2 to 188 (mean, 43) days after inoculation. Inoculum oocysts were also observed in the cecum and/or large intestine of certain of the twenty-six hibernators inoculated with 100,000 to 1,000,000 oocysts and necropsied during hibernation. Inoculum oocysts of all three species studied, recovered during hibernation from certain squirrels caused infections when inoculated into susceptible room-active squirrels. In hibernators with pretorpid intervals of 1 to 3 days, 90, 54, and 84 percent became infected with E. bilamellata, E. larimerensis, and E. callospermophili, respectively; in squirrels with pretorpid intervals of 4 or more days these values were 83, 75, and 71, respectively. Fourteen squirrels from both groups began to discharge oocysts resulting from an infection before or during hibernation and thirty-six did so after removal from the chamber during February through April. Infections in room-active juvenile and adult squirrels occurred after inoculation with E. bilamellata and E. larimerensis in 90 and 58, and 93 and 64 percent, respectively; 100 percent of the room-active squirrels became infected after inoculation with E. callospermophili. Except for hibernators with pretorpid intervals of 1 to 3 days after inoculation with E. bilamellata the total numbers of oocysts discharged from infections in the room-active groups was greater than that from corresponding infections in the hibernating groups. Within 30 days after completion of hibernation the squirrels were reinoculated with 40,000 sporulated oocysts of the same species received before hibernation. Such reinoculations with E. callospermophili usually resulted in infections, with greater discharges of oocysts than in the original infections; this also held true, but to a lesser degree, for E. larimerensis. Few squirrels became reinfected with E. bilamellata and these discharged fewer oocysts than in original infections. Results obtained after reinoculation of hibernators with E. bilamellata and E. callospermophili were similar to those obtained after corresponding reinoculations of room-active squirrels with the same two species. More squirrels became infected and greater numbers of oocysts were discharged after reinoculations of hibernators with E. larimerensis than after similar reinoculations of room-active squirrels. These findings indicate that the oocysts and/or early developmental stages survive in torpid squirrels during the hibernating period. They also indicate that certain stages of E. bilamellata survive better than those of other species during hibernation.

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