STRATEGIES TO CONTROL TAPEWORMS IN PETS
Tapeworms in dogs and cats can be treated with praziquantel, epsiprantel, or fenbendazole. Praziquantel and epsiprantel are considered the treatments of choice because they are highly effective against Dipylidium caninum—the most common tapeworm in dogs and cats—as well as Taenia and Echinococcus species, although only praziquantel is labeled as effective against Echinococcus species; fenbendazole is not effective against D. caninum and is not labeled against Echinococcus species.8 Praziquantel also has been used successfully to treat pseudophyllidean tapeworms, but this application requires a higher-than-labeled dose and extended duration of treatment (25 mg/kg orally for two consecutive days2 ).
Figure 3. A Taenia species egg. The eggs are shed individually and have thick striated walls and clearly visible refractile hooks. They measure 30 to 40 μm in diameter.
However, to be effective, treatment of tapeworm infections in dogs and cats must be combined with appropriate management modifications. For example, stringent adherence to controlling fleas and lice is required to prevent D. caninum infections. Preventing predation and scavenging activity by keeping cats indoors and dogs confined to a leash or in a fenced yard will limit the opportunity for pets to acquire infection with Taenia, Echinococcus, or Spirometra species or Diphyllobothrium latum through ingestion of intermediate hosts. In the absence of these changes, reinfection is likely to occur.1 Because both flea infestations and scavenging behaviors are difficult to prevent entirely, routine monthly deworming of some dogs and cats with a broadly cestocidal compound such as praziquantel may be indicated, particularly for dogs and cats in areas where Echinococcus species is endemic.
Figure 4. A Spirometra species egg. Spirometra species shed operculate, hen-egg-shaped ova that are about 65 μm long by 35 μm wide.
In North America, Echinococcus species infections in people are rare6 ; isolated reports of zoonotic infection with larval Taenia species of dogs and cats also exist.9 Although the overall risk of human infection with these parasites in North America is extremely low, dogs and cats infected with these tapeworms do create a potential zoonotic risk. Taenia and Echinococcus species eggs shed in the feces of an infected dog or cat are immediately infectious to the intermediate host.1 People who consume these eggs may develop cestode cysts requiring drainage, surgical removal, or extended chemotherapy. In the case of Echinococcus multilocularis, surgery is unlikely to be successful, and long-term anthelmintic therapy may be required.6
Dipylidium caninum infections in children who have ingested infected fleas are occasionally reported.10 The disease induced in children is generally mild, confined to the intestinal tract, and readily treated but can still be distressing to the families. People are a normal definitive host of Diphyllobothrium latum and may become infected with this tapeworm after ingesting larvae in raw fish.1
Spirometra species are also zoonotic; people who inadvertently ingest Spirometra species-infected copepods in water or spargana in the tissue of an infected second intermediate host can develop the larval form. In North America, people with Spirometra species infections usually present with flocculent subcutaneous masses; larvae have also been reported to develop in ocular tissue and in the central nervous system.2
Editors' note: Dr. Little has received research funding from Bayer Animal Health.
Susan E. Little, DVM, PhD, DEVPC
Department of Veterinary Pathobiology
Center for Veterinary Health Sciences
Oklahoma State University
Stillwater, OK 74078