Cestode infections in dogs and cats in North America are common, but their incidence may be underestimated because diagnostic techniques for intestinal parasites do not typically identify tapeworm infections. Cestode life cycles are indirect; dogs and cats are commonly definitive hosts and the adult tapeworm is found in the small intestine. Occasionally cats and dogs are infected as intermediate hosts and carry the immature metacestode stages in various tissues. Most tapeworm infections in North America are due to Dipylidium caninum (dogs and cats), Taenia pisiformis (dogs), and Taenia taeniaeformis (cats). It is unusual for infections to result in serious clinical disease; however, there are public health concerns as well as pet owner discomfort from observation of the proglottids. Human infection does occur, primarily in young children, when the intermediate host is accidently ingested.
Taenia species are seen in animals that hunt, as the immature stages occur primarily in rodents. Fleas and lice are the intermediate hosts for D caninum so infection is fairly common. Infection with Mesocestoides, other Taenia species, and Spirometra are less common, but do occur and can cause life-threatening disease. Echinococcus multilocularis and Echinococcus granulosus occur in only a small segment of North America, but because these tapeworms can cause serious human disease, control measures are important.
