Development of second-generation schizonts, gamonts and oocysts of Eimeria bovis in bovine kidney cells.

Abstract

First-generation merozoites of Eimeria bovis, obtained from calves which had been inoculated 14, 14 1/2 and 15 days earlier, were inoculated into monolayers of Madin-Darby bovine kidney (MDBK) and primary embryonic bovine kidney (BEK-1), as well as kidney cell aggregates (BEK-2). Cultures were examined at intervals of 1–12 hr for 168 hr with phase-contrast microscopy and then fixed, stained and re-examined with bright-field microscopy. Fourteen-day merozoites entered all cell types, whereas 14 1/2- and 15-day merozoites did not enter any. Development beyond the first-generation merozoite stage occurred in BEK-1 and BEK-2, but not MDBK. Intermediate and mature second-generation schizonts with 24–36 merozoites were seen at 48–108 hr. Merozoites were 4.5 by 1.4 μm, with a posteriorly located nucleus. Young, intermediate, and mature microgamonts were seen at 72–96 hr, 72–120 hr, and 96–120 hr, respectively. Young, intermediate, and mature macrogamonts were seen at 48–96 hr, 72–120 hr, and 96–120 hr, respectively. Mature microgamonts and macrogamonts were 14.7 μm in diameter and 19.5 by 15 μm, respectively. At 120–168 hr, zygotes in various stages of oocyst wall formation and oocysts (24.4 by 15 μm) were seen. A crescent body was present in the parasitophorous vacuole of some schizonts and gamonts.