Veterinary Medicine - May 2008 - (Page v2) Tapeworms: What you need to know Key Points • Dipylidium caninum is the most common tapeworm in North American dogs and cats. • Dipylidium infection occurs by ingesting infected fleas. • Taenia infection occurs by ingesting infected mammals. • Infection rates of Dipylidium depend on the flea prevalence in a particular area. • D. caninum infection is a common tapeworm in dogs and cats in the continental United States.2 • Animals can become infected with Dipylidium even though they are receiving appropriate flea control. • Just a few fleas can propagate a tapeworm infection. Common Tapeworm infection: It’s often overlooked, underdiagnosed, and undertreated in dogs and cats throughout the United States. To reverse this trend, it’s imperative that veterinarians and their team members understand and thoroughly educate clients about the risk of tapeworm zoonoses and the importance of prevention. This Q&A, moderated by Dr. Byron Blagburn, examines the prevalence and life cycle of common tapeworms and discusses strategies the veterinary team can use to manage and prevent infection. Q: What is the most common tapeworm species, and what is its life cycle? Susan Little: Dipylidium caninum is the most common tapeworm in North American dogs and cats. As most veterinary professionals know, it is acquired by ingesting infected fleas. A dog or cat with a Dipylidium caninum adult in its small intestine sheds egg-filled proglottids in its feces, and those proglottids in the environment are consumed by flea larvae. As the flea larva matures into an adult flea, the tapeworm egg develops into an infectious cysticercoid. When a dog or cat ingests the adult flea, the cysticercoid emerges in the animal’s small intestine. The protoscolex attaches to the wall of the small intestine, where the adult tapeworm forms. It is a rapid process. Within two to three weeks of ingesting an infected flea, a dog or cat can shed proglottids in its feces. Byron Blagburn: Would the same process occur if a small child happened to ingest a flea? Little: Yes. Dipylidium tapeworms can develop and produce proglottids in a child when that child inadvertently ingests a flea containing the cysticercoid. The tapeworm will continue to develop in that child’s small intestine, and the parents may find proglottids in the diaper or on the anus. Cat flea (Ctenocephalides felis) Flea Pupae Pupae may hatch within seven to 14 days or may be dormant for months. Q: Adult Fleas Adult fleas lay eggs within 24 to 48 hours. How prevalent is Dipylidium infection? Little: The estimates for infection rates are all over the map—from 4% to 50% or higher. It really depends on the flea prevalence in a particular area—the prevalence of Dipylidium follows. In addition, the proglottids are not evenly distributed throughout the feces. So if you do a fecal flotation on just 4 grams of feces, the odds of finding a proglottid are low. Fecal exams Flea Eggs Flea Larvae The larval stage lasts from five to 11 days. The eggs can hatch within one to six days.
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