Life cycle of Taenia multiceps
and T. serialis
, canid tapeworms that cause coenurosis in humans
The definitive hosts for the cestodes (tapeworms) Taenia multiceps and T. 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 (bisexual reproductive segments) 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 (inanimate objects or substances capable of transferring pathogens) 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.
From Centers for Disease Control Parasites and Health website