Eimeria bovis is one of the many bovine gastrointestinal parasites, and it is
ubiquitous in the environment. It has a general form of coccidian life cycle,
including both asexual multiplication and sexual multiplication.
Sexual multiplication culminates in the formation of oocysts, which
are discharged with the feces (A). Four
sporoblasts develop within each oocyst (B), and
two infective sporozoites develop within each sporocyst (C).
() Following the
ingestion of sporulated oocysts by calf (D),
the sporozoites invade the epithelial cells (E) or the lamina propria of the host's small
intestine. Click on the small intestine to get a closer view
of Eimeria life cycle or click anywhere on the closeup diagram to return to the over view. Sporozoites inside host cells
can round up as a trophozoite (F),
grow larger, and become a first generation schizont, or a megaschizont (G). The megaschizont then
releases many merozoites which further infect fresh host cells (H). There may be several more
schizogonic generations for other Eimeria, but two or three is usually the limit
for may of the important species.
Click on the large intestine to get a closer view of Eimeria
life cycle or click anywhere on the closeup diagram to return to
the over view. A merozoite produced by the final schizogony is a telomerozoite
(I). Telomerozoites can
enter a fresh host cell and develop into either a male or a female gametocyte
or developing sex cell (J).
The female gametocyte enlarges, stores food materials, and induces hypertrophy of
both cytoplasm and nucleus of its host cell. When mature, it is called a macrogamete
or female sex cell. The male gametocyte undergoes repeated nuclear division nd
becomes multinucleate. Each nucleus is finally incorporated into a biflagellate microgamete
or male sex cell. Only a small fraction will find and fertilize macrogametes to form
The oocyst is released by rupture of the host cell and passes out with the feces to
undergo sporulation, provided that the environment is adequate.