Then, an intermediate host (the larval stage of a flea or chewing louse) will ingest an egg, which develops into a cysticercoid larva. The cysticercoid larva remains viable, but is not infective to carnivores until the flea hatches to an adult and begins feeding on a host (e.g. a dog). Approximately 36 hours after the flea has consumed a blood meal, the infective metacestode develops inside the flea. The metacestode larva must be ingested in a flea by the dog or cat during grooming in order to develop. Humans can also become infected by D. caninum by accidentally ingesting an infected flea. In the small intestine of the definitive host, the metacestode develops into an adult tapeworm, which reaches maturity 4-6 weeks after ingestion. This adult tapeworm produces proglottids, and over time, the proglottids mature and become gravid and eventually detach from the tapeworm and the life cycle starts all over again. Geographic Distribution
This parasite occurs worldwide in animals, such as dogs and cats, as well as in humans, though to a significantly lesser degree. It is the most common tapeworm of dogs and is relatively common in cats. Despite human diplydiasis being rare, instances have been reported from every inhabited continent.Human instances of diplydiasis are reported globally, and unsurprisingly roughly one third of the cases occur in children less than 6 months of age. The most at-risk age group is those that range from 2 months to 4 years old.
Pet infections
Tapeworm infection usually does not cause pathology in the dog or cat, and most pets show no adverse reaction to infection other than increased appetite. The bulk of infections are asymptomatic and the infections that do result in symptoms are generally mildly so. Pets behavior may reflect the presence of anal discomfort and itching, or pruritus. This could result in the ‘butt-scooching” across the floor, grass or carpeting. It may be accompanied by slight gastrointestinal disturbances, as this is the region where the worms inhabit. Though not a pathology of the diplydiasis, the most unnerving sign of the infection is the presence of proglottids in the animals, or child’s, feces. These proglottids can also be found near the perianal region, in the feces, and in diapers (children). The motile proglottids can actively crawl out of the anus of the infected animal/person and migrate small distances, thus potentially covering this array of neighboring surfaces. It is from these locations that the larval stage of the flea will come along and ingest them. Then the metacestode stage, a cysticercoid, develops in the coelomic cavity (abdominal cavity; main body cavity) of the flea larvae and remains there as the flea matures into an adult. These freshly passed proglottids are motile, allowing them to also be found on the floor and furniture, from a migration out of a pets anus and could be compared to resembling fly larvae, or maggots.The other tapeworm infecting cats is Taenia taeniaeformis, though this form is much less commonly encountered than D. caninum.