SUMMARY
A flock of Northern bobwhites (Colinus virginianus) reared for release as game birds and commercial meat production were experiencing clinical coccidiosis. Fecal samples were collected and recovered oocysts had average measurements of 22.9 (19.7–25.3) μm by 18.8 (16.7–20.9) μm; the morphometrics and morphology of the oocysts were consistent with those of Eimeria lettyae Ruff 1985, which possess a nonrefractive polar granule and asymmetrical sporocysts. Experimental infections using oocysts propagated from the field sample were used to determine the complete development of the coccidium and to analyze oocyst production. Birds inoculated with 100, 400, 1000, and 4000 oocysts began shedding the parasites 4 days postinoculation; shedding persisted for 3–7 days. Oocyst shedding peaked on Day 5 for birds inoculated with the two lower doses administered (i.e., 100 and 400 oocysts) and peaked a day later for birds provided with the two higher doses (i.e., 1000 and 4000 oocysts). Although total oocyst output (233,132,050 oocysts/bird) was greatest in the Northern bobwhites that received 4000 oocysts, the fecundity of E. lettyae was nearly three times higher in birds infected with 1000 oocysts (fecundity = 173,324) than birds gavaged with 4000 oocysts (fecundity = 58,283). To examine the endogenous development of the parasite histologically, Northern bobwhites were inoculated with various doses of the Eimeria sp. every 3 or 6 hr throughout the estimated prepatent period determined during the analysis of parasite shedding. Four generations of merogony and gametogony were observed in the duodenum and jejunum, and the prepatent period was estimated to be 90–96 hr. Similarities to previous descriptions of E. lettyae support the identification of this parasite in the infected flock of Northern bobwhites. Sequences of the complete mitochondrial genome (GenBank PQ178945) and two variants of the partial nuclear 18S ribosomal DNA (GenBank PQ186547 and PQ186548) were generated using polymerase chain reactions and Sanger sequencing to aid in future diagnoses of E. lettyae.