Eimeria bovis

Life Cycle

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). 

(or_da_ar.gif (344 bytes))  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 oocysts

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. 

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Parasites and Parasitic Diseases of Domestic Animals
Dr. Colin Johnstone (principal author)
Copyright 1998 University of Pennsylvania
This page was last modified on January 24, 2000