Inoculation of northern bobwhite quail (Colinus virginianus) with low doses of Eimeria lettyae oocysts stimulates a protective immune response, suggesting immunization may be an option for controlling coccidiosis. However, the oocyst production of inoculated birds could be considerable, leading to subsequent outbreaks. To determine the oocyst production following inoculation with E. lettyae, we orally infected 12-wk-old bobwhites with 100, 1,000, or 10,000 sporulated oocysts. Fecal materials were collected on days 5–9 post-inoculation, and total oocyst production was counted in McMaster chambers. Oocyst production/bird was 49.75, 89.5, and 436 × 106 for 100, 1,000, or 10,000 oocysts administered, respectively. Estimated oocysts produced/oocyst administered was 49.75, 8.95, and 4.36 × 104 for 100, 1,000, or 10,000 oocysts administered, respectively. These findings not only illustrate the crowding effect of larger oocyst inocula but also illustrate the fecundity of E. lettyae at low doses. This suggests that successful immunization of bobwhites against coccidiosis with live vaccines might require attenuated strains with reduced reproductive potential.

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