Tapeworms in Dogs and Cats

Most urban dogs and cats eat prepared foods and have restricted access to natural prey. Such animals still may acquire Dipylidium caninum (the double-pored dog tapeworm) by ingesting fleas during grooming. Cats with access to infected house (or outdoor) mice and rats also can acquire Taenia taeniaeformis. In certain parts of the world (eg, India, the Middle East, North Africa, southeast Asia, southern Europe), dogs and cats with access to reptiles may acquire Joyeuxiella pasqualei. Suburban, rural, and hunting dogs have more access to various small mammals, in addition to raw meat and offal from domestic and wild ungulates. A number of cestodes can be expected in such dogs (see Table: Cestodes of Dogs and Cats in North America). On sheep ranges and wherever wild ungulates and wild canids are common, dogs may acquire Echinococcus granulosus (the hydatid tapeworm). Sylvatic Echinococcus multilocularis (the alveolar hydatid tapeworm), previously known only from arctic North America, has been found in wildlife in midwestern and western USA and Canada. The parasite is also endemic in many parts of central and eastern Europe, particularly France, Germany, and Switzerland. Thus far, infections in cats or dogs are generally rare. However, in addition to multiple reports from dogs and cats in central Europe, the parasite has recently been identified in a few dogs across Canada. Spirometra mansonoides is an uncommon (but not rare) parasite of cats and occasionally of dogs along the eastern and Gulf Coast areas of North America.

Association with infected dogs may result in human infection with metacestodes of E granulosus, E multilocularis, T multiceps, T serialis, or T crassiceps in various tissues (by ingestion of eggs passed in dog feces), or adult D caninum in the intestine (by ingestion of infected fleas). The presence of metacestodes in livestock may limit commercial use of such carcasses or offal meats. Thus, cestodes of dogs and cats may be of both economic and public health importance (see Table: Cestodes of Public Health Importance).

Adult cestodes in the intestine of dogs and cats rarely cause serious disease, and clinical signs, if present, may depend on the degree of infection, age, condition, and breed of host. Clinical signs vary from unthriftiness, malaise, irritability, capricious appetite, and shaggy coat to colic and mild diarrhea; rarely, intussusception or blockage of the intestine, emaciation, and seizures are seen.

Diagnosis is based on finding proglottids or eggs in the feces. The eggs of Taenia spp and Echinococcus spp cannot be differentiated by microscopic examination; PCR methods are required. Direct microscopic examination of fecal samples or fecal flotation may reveal the eggs of Spirometra mansonoides, which are sometimes mistaken for trematode eggs, although they are larger and possess an operculum that is often difficult to see.

Control of tapeworms of dogs and cats requires therapy and prevention. Animals that roam freely often become reinfected by ingestion of metacestodes in carrion or prey animals. Dipylidium caninum is different, because it can cycle through fleas that may be associated with confined infected animals. An accurate diagnosis is necessary for effective advice on preventing reinfection.

Effective treatment should remove the attached scolices from the small intestine of infected animals. (See table: Cestodes of Dogs and Cats in North America for specific approved treatments.) For dogs, fenbendazole and praziquantel are approved for treatment of Taenia spp (ie, more than just T pisiformis, for which epsiprantel is approved); epsiprantel, nitroscanate, and praziquantel are approved for D caninum; and praziquantel is approved for treatment of Echinococcus spp (see Table: Drugs for Intestinal Helminths of Dogs Approved in the USA and UK). For cats, fenbendazole and praziquantel are approved for treatment of Taenia spp (ie, more than just T taeniaeformis, for which epsiprantel is approved); epsiprantel and praziquantel are approved for treatment of D caninum, and praziquantel is approved for treatment of E multilocularis (see Table: Drugs for Intestinal Helminths of Cats Approved in the USA and UK). Outside the USA and UK, praziquantel is approved for use in multiple countries at 5 mg/kg for treatment of J pasqualei in dogs (as praziquantel/pyrantel/febantel) and cats (as praziquantel/pyrantel).

Praziquantel at 7.5 mg/kg, PO, for 2 consecutive days is effective against Diphyllobothrium sp in dogs. Furthermore, a single dose of 35 mg/kg, PO, eliminates D latum from infected cats. Both treatments are extra-label.

Infections with Spirometra sp in dogs and cats can be treated with praziquantel at 7.5 mg/kg, PO, for 2 consecutive days. Spirometra sp infections in cats can also be treated with a single dose of praziquantel at 30 mg/kg, SC, IM, or PO. Mebendazole at 11 mg/kg, PO, has also been successful. All these treatments are extra-label.