Biology

Causal Agent

Dipylidium caninum is a common tapeworm of dogs and cats, but is occasionally found in humans. It has many common names including the “flea tapeworm”, “cucumber tapeworm”, and “double-pored tapeworm”.

Life Cycle

Gravid proglottids are passed intact in the feces or emerge from the perianal region of the host image . In the environment, the proglottids disintegrate and release egg packets, which are also occasionally found free in the feces image . The intermediate host (most often larval stages of the dog or cat flea Ctenocephalides spp.) ingests egg packets, and the oncosphere within is released into the larval flea’s intestine. The oncosphere penetrates the intestinal wall, invades the insect’s hemocoel (body cavity), and develops into a cysticercoid image . The cysticercoid remains in the flea as it matures from a larva into an adult image . The vertebrate host becomes infected by ingesting the adult flea containing the cysticercoid image . In the small intestine of the vertebrate host, the cysticercoid develops into the adult tapeworm after about one month. The adult tapeworms (measuring up to 60 cm in length and 3 mm in width) reside in the small intestine of the host, where they each attach by their scolex image . Gravid, double-pored proglottids detach from the strobila (body) and are shed in the feces.

Humans also acquire infection by ingesting the cysticercoid contaminated flea. Children are most frequently infected, possibly due to close contact with flea-infested pets image .

Hosts

Canids and felids are the normal hosts for Dipylidium caninum. The intermediate host is usually the larval stages of the dog or cat flea (Ctenocephalides spp.) and occasionally Trichodectes canis (the dog louse).

Geographic Distribution

Worldwide; this tapeworm is ubiquitous and common among pet dogs and cats. Human infection is rare, but has been reported from every inhabited continent.

Clinical Presentation

Most infections with Dipylidium caninum are asymptomatic. Pets may exhibit behavior to relieve anal pruritis (such as scraping anal region across grass or carpeting). Mild gastrointestinal disturbances may occur. The most striking feature in animals and children consists of the passage of proglottids. These can be found in the perianal region, in the feces, on diapers, and occasionally on floor covering and furniture. The proglottids are motile when freshly passed and may be mistaken for maggots or fly larvae.

Page last reviewed: July 10, 2019