Life Cycle and Host Specificity of Eimeria larimerensis Vetterling, 1964, from the Uinta Ground Squirrel Spermophilus armatus1

Abstract

SYNOPSIS. Eimeria larimerensis was found in 5 species of ground squirrels and the white‐tailed prairie dog. The hosts included Spermophilus armatus from Utah and Montana, S. variegatus from Utah, S. tridecemlineatus from Wyoming, S. lateralis from Utah, S. beecheyi from California and Cynomys leucurus from Wyoming. Oocysts were not present in fecal samples of S. richardconi from Montana, S. lateralis from California or S. columbianus from Washington. This coccidium could not be experimentally transmitted to S. richardsoni; however, patent infections were established in S. armatus, S. lateralis, and S. variegatus. No infections were found after inoculation of least chipmunks (Eutamius minimus), Mongolian gerbils (Meriones unguiculatus), or laboratory rats even tho excystation occurred in these animals. Resistance to infection did not develop during repeated experimental infections of S. armatus, S. lateralis, or S. variegatus. No outward signs of coccidiosis were seen in any of the experimentally infected animals.In experimentally infected S. armatus, the prepatent period was 5 days, and the patent period lasted 3–7 (mean 6.5) days. The endogenous stages were located in the epithelial cells of the jejunum and ileum. Mature 1st‐generation schizonts, 1st seen 2.5 days after inoculation, contained 16–32 merozoites. Mature 2nd generation schizonts were present 3.5 days after inoculation and contained 22–46 merozoites of a larger size than those of the 1st generation. Gametocytes were 1st seen 3.5 days after inoculation and developing oocysts were present 4 days after inoculation. Macrogametes contained eosinophilic granules which coalesced to form the oocyst wall. Formation of the macrogametes took place around cytoplasmic masses within the microgametocytes.