Coenurosis: life cycle

The definitive hosts for Taenia multiceps and Taenia serialis are members of the family Canidae. Many canids can serve as definitive hosts for T. multiceps, but only dogs and foxes can serve as hosts for T. serialis. Eggs and gravid proglottids are shed in feces into the environment (1), where they are ingested by an intermediate host (2). Many animals may serve as intermediate hosts, including rodents, rabbits, horses, cattle, sheep, and goats. Eggs hatch in the intestine, and oncospheres are released (3) that circulate in blood until they lodge in suitable organs (including skeletal muscle, eyes, brain, and subcutaneous tissue). After about three months, oncospheres develop into coenuri. The definitive host becomes infected by ingesting the tissue of an infected intermediate host containing a coenurus (4). The adult cestodes reside in the small intestine of the definitive host (5,6). Humans become infected after the accidental ingestion of eggs on fomites or in food and water contaminated with dog feces (7). Eggs hatch in the intestine, and oncospheres are released (8) that circulate in blood until they lodge in suitable organs and after about three months develop into coenuri (9). Coenuri of T. multiceps are usually found in the eyes and brain; those of T. serialis are usually found in subcutaneous tissue.