Courtesy of Dr. Andrew Peregrine.
Courtesy of Dr. Andrew Peregrine.
Courtesy of Dr. Andrew Peregrine.
Courtesy of Dr. Andrew Peregrine.
Courtesy of Dr. Andrew Peregrine.
Tapeworms of dogs and cats have indirect life cycles with adult tapeworms located in the animals' small intestine and the larval (metacestode) stage found in an intermediate host. Dogs and cats become infected by ingestion of the infected intermediate host. 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. In many parts of the world, such infections appear to be common. Cats with access to infected house (or outdoor) mice and rats also can acquire Taenia taeniaeformis.
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) Globally, the two most important are Echinococcus granulosus sensu lato (the hydatid tapeworm) and Echinococcus multilocularis (the alveolar hydatid/fox tapeworm).
On sheep ranges and wherever wild ungulates and wild canids are common, dogs may acquire E granulosussensu lato. DNA analysis has indicated that E granulosus sensu lato is a species complex that comprises E granulosus sensu stricto (sheep/buffalo strains G1, G2, G3), Echinococcus equinus (horse strain G4), Echinococcus ortleppi (cattle strain G5), Echinococcus intermedius (camel strain G6, pig strain G7), and Echinococcus canadensis (cervid strains G8, G10). Dogs are definitive hosts for all these species. Furthermore, all except E equinus are a public health concern. E multilocularishas been found in wildlife in arctic North America, midwestern US, and southern Canada (British Columbia east to Ontario). The parasite is also endemic in many parts of central and eastern Europe, particularly France, Germany, and Switzerland, and in China.
Thus far, intestinal infections in dogs, and to a much lesser extent cats, are generally uncommon (< 1%); however, they are a noteworthy public health concern. Furthermore, in addition to developing intestinal infections from ingestion of infected rodents, dogs may develop alveolar echinococcosis (disease due to the larval stage of the parasite, typically in the liver) from ingestion of parasite eggs, eg, in feces of wild canids. Such infections, while uncommon, have been diagnosed in multiple dogs in central Europe, across southern parts of Canada, and in Virginia, US.
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 and also parts of South America. Other species occur in Asia, Australia, and Europe. Infections are acquired by ingestion of the parasites' second intermediate host (amphibians, reptiles, birds).
In parts of southern Europe and the Middle East, cats with access to reptiles can become infected with Diplopylidium nölleri. 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.
Cestodes of Dogs and Cats in North America
Cestode | Definitive Host | Intermediate Host and Organs Invadeda | Diagnostic Features of Adult Worm | Comments | Approved Treatmentb |
|---|---|---|---|---|---|
Dipylidium caninum | Dog, cat, coyote, wolf, fox, other wild canids and felids | Fleas and more rarely lice; free in body cavity | Strobila 15–70 cm long and up to 3 mm in maximum width. Segments shaped like cucumber seeds, with pore near middle of each lateral margin. | Probably most common tapeworm of dogs and cats; cosmopolitan. Occasionally infects humans, particularly infants. | Dogs and cats: epsiprantel, praziquantel |
Taenia taeniaeformis | Cat, dog, lynx, fox, other animals | Various rats, mice, other rodents; in large cysts in liver | Strobila 15–60 cm long, 5–6 mm in maximum width. No neck. | Common cestode of cats, rare in dogs; cosmopolitan | Cats: epsiprantel, praziquantel, fenbendazole |
Taenia pisiformis | Dog, fox, wolf, coyote, other animals | Rabbits and hares, rarely squirrels and other rodents; in pelvic or peritoneal cavity attached to viscera | Strobila 60 cm to 2 m long, 5 mm in maximum width. | Particularly common in suburban, farm, and hunting dogs that eat rabbits and rabbit viscera. | Dogs: epsiprantel, fenbendazole, praziquantel |
Taenia hydatigena | Dog, wolf, coyote, weasel, fox | Domestic and wild cloven-hoofed animals, rarely hares and rodents; in liver and abdominal cavity | Strobila to 5 m long and 7 mm in maximum width. | In farm dogs, more rarely hunting dogs; cosmopolitan | Dogs: praziquantel, fenbendazole |
Spirometra mansonoides | Cat, dog, raccoon, bobcat | Copepods, frogs, rodents, snakes; connective tissue | Strobila 0.5 m long, 8 mm in maximum width. Scolex with 2 grooves and no hooks. Genital pores ventral midline of segment. | Eastern and Gulf Coast, North America | See text for extra-label treatment |
Diphyllobothrium (Dibothriocephalus) spp | Humans, dog, cat, other fish-eating animals | Encysted in various organs, or free in body cavity of various fish | Strobila to 10 m long, 20 mm in maximum width but usually smaller. Scolex with 2 grooves (bothria) and no hooks. Genital pores ventral midline of segment. | Canada; Alaska and other states of the US; Siberia; and other areas | See text for extra-label treatment |
Echinococcus granulosus sensu lato | Dog, wolf, coyote, fox, and several other wild carnivores | Sheep, goats, cattle, pigs, horses, deer, moose, some rodents, occasionally humans and other animals; commonly in liver and lungs, occasionally in other organs and tissues | Strobila 2–6 mm long with 3–5 segments; rostellar hooks in double row. | Foci among North American range sheep and dogs associating with them; sylvatic moose-wolf cycle where these animals are found; found globally. | Dogs: praziquantel |
Echinococcus multilocularis | Arctic, red, and gray foxes; coyote; cat; dog | Microtine rodents, occasionally in humans; in the liver and other organs | Strobila 1.2–2.7 mm long with 2–4 segments; rostellar hooks in double row. | China, central and eastern Europe, former USSR, Alaska, and midwestern US and Canada; thus far, a sylvatic transmission cycle involving cats and dogs in North America not recognized. However, multiple cases of alveolar echinococcosis have been diagnosed in dogs across southern Canada and central Europe. | Dogs and cats: praziquantel for intestinal infections |
Mesocestoides spp | Many wild canids, felids, mustelids; other animals, including dog and cat | Complete life cycle unknown; arthropod intermediate hosts suspected; juvenile tetrathyridia in abdominal cavity and elsewhere in various mammals, birds, and reptiles; tetrathyridia in intestine of dogs may enter abdomen via intestinal wall, resulting in peritoneal larval cestodiasis. Thoracic tetrathyridiosis has been reported in dogs and cats but is very rare. | Strobila 10 cm long and 2–5 mm wide. Scolex with 4 suckers but no rostellum or hooks. Genital pore ventral in midline of worm. Gravid segments with parauterine organ. | Reported in dogs and cats in midwestern and western US; in wild animals elsewhere in US and Canada | Dogs: praziquantel |
Taenia multiceps | Dog, coyote, fox, wolf | Sheep, goats, and other domestic or wild ruminants, rarely humans; usually in brain or spinal cord | Strobila 40–100 cm long and up to 5 mm wide. Scolex with 4 suckers and hooks in double row. | Rare in domestic carnivores in western North America; more common in wild animals | Dogs: praziquantel, fenbendazole |
Taenia serialis | Dog, coyote, fox, wolf | Rabbit, hare, squirrel, rarely humans; in subcutaneous connective tissue or retroperitoneally | Strobila 20–72 cm long and 3–5 mm wide; hooks in double row. | Primarily in wild canids; considered by some authorities as not distinct from T multiceps | Same as for T multiceps |
Taenia crassiceps | Dog, coyote, fox, wolf | Various rodents, a few records in humans; subcutaneous and in body cavities | Strobila 70–170 mm long and 1–2 mm wide. Scolex with hooks in double row. | Reported from Canada and northern US, including Alaska | Same as for T multiceps |
Taenia krabbei | Dog, coyote, wolf, bobcat | Moose, deer, reindeer; in striated muscle | Strobila ~20 cm long and up to 9 mm wide. Scolex small with hooks in double row. | Reported from Canada and northern US, including Alaska; considered by some a subspecies of T ovis | Same as for T multiceps |
Taenia ovis | Dog, wild canids | Sheep and goat; in skeletal and cardiac muscle, rarely elsewhere | Strobila 45–110 cm long and up to 4–8.5 mm wide. Scolex with hooks in double row. | Reported from western and central Canada and the southern US | Same as for T multiceps |
a In all cases in which the life cycle is known, cats and dogs become infected by eating animals (or parts) that contain the infective metacestode. These intermediate hosts become infected by ingesting tapeworm eggs (except in Mesocestoides, Spirometra, and Diphyllobothrium spp, which have an extra stage in the life cycle), which are passed in the feces of the definitive host. | |||||
b See table Drugs for Intestinal Helminths of Dogs Approved in the US and UK and Drugs for Intestinal Helminths of Cats Approved in the US and UK for drug dosages. | |||||
Association with infected dogs may result in human infection with metacestodes of E granulosus, E multilocularis, Taenia multiceps, Taenia serialis, or Taenia 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 production animals 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).
Cestodes of Public Health Importance
Cestodea | Host of Adult Worm | Name of Metacestode (Intermediate) Stage | Measurements of Metacestode | Principal Intermediate Hosts | Site of Metacestode |
|---|---|---|---|---|---|
Taenia saginata | Humans only | Cysticercus “beef measles” | 9 × 5 mm | Cattle | Skeletal and cardiac muscle |
Taenia solium | Humans only | Cysticercus “pork measles” | 6–10 × 5–10 mm | Pigs, rarely dogs (humans may be both definitive and aberrant intermediate hosts) | Skeletal and cardiac muscle, occasionally nervous system |
Diphyllobothrium spp | Humans, dogs, cats, and other fish-eating mammals | Procercoid in copepod, plerocercoid in fish | 2–25 × 2.5 mm for plerocercoid | Copepod, then fish | Mesenteric tissues, testes, ovary, muscles of fish |
Echinococcus granulosus sensu lato | Dogs, wolves, foxes, and several other wild carnivores | Hydatid cyst | Diameter 50–100 mm, sometimes ≥150 mm | Sheep, cattle, pigs, horses, moose, deer, occasionally humans | Commonly in liver and lungs, occasionally in other organs and tissues |
Echinococcus multilocularis | Canids and domestic cats | Alveolar hydatid cyst | Variable | Field mice, voles, lemmings, sometimes domestic mammals and humans | Usually liver, various other organs and tissues |
a Human infections with the metacestodes of Taenia crassiceps, Taenia multiceps, Mesocestoides spp, and other cestodes not listed here occur rarely. Children occasionally become infected with adult Dipylidium caninum, which appears to have no medical significance but important aesthetic aspects. | |||||
Clinical Signs of Tapeworms in Dogs and Cats
Adult cestodes in the intestine of dogs and cats rarely cause disease, and clinical signs, if present, may depend on the extent 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 occur.
Diagnosis of Tapeworms in Dogs and Cats
Courtesy of Dr. Andrew Peregrine.
Diagnosis of tapeworm is based on finding proglottids or eggs in the feces. However, all fecal flotation methods have low sensitivity. It should also be noted that the eggs of Taenia spp and Echinococcus spp cannot be differentiated by microscopic examination; PCR assay methods are required. Fecal sedimentation or fecal flotation may reveal the eggs of Diphyllobothrium or Spirometra spp, which, unlike more common tapeworms, lack hooks; they are sometimes mistaken for trematode eggs, although they are larger and possess an operculum that is often difficult to see.
In some parts of the world, fecal antigen tests for Echinococcus spp are available.
Treatment and Control of Tapeworms in Dogs and Cats
Control of tapeworms of dogs and cats requires treatment and prevention. An accurate diagnosis is necessary for effective advice on preventing reinfection. Animals that roam freely often become reinfected by ingestion of metacestodes in carrion or prey animals. D caninum is different, because it can cycle through fleas that may be associated with confined infected animals.
Effective treatment includes removal of 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: 1) fenbendazole and praziquantel are approved for treatment of Taenia spp; epsiprantel is approved for just Taenia pisiformis; 2) epsiprantel, nitroscanate, and praziquantel are approved for D caninum; and 3) praziquantel is approved for treatment of Echinococcus spp ( see Table: Drugs for Intestinal Helminths of Dogs Approved in the US and UK).
For cats: 1) fenbendazole and praziquantel are approved for treatment of Taenia spp; epsiprantel is approved for just T taeniaeformis; 2) epsiprantel and praziquantel are approved for treatment of D caninum; and 3) praziquantel is approved for treatment of E multilocularis ( see Table: Drugs for Intestinal Helminths of Cats Approved in the US and UK).
Outside the US 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). In the UK, EU, India, and other countries, praziquantel is approved at 10 mg/kg for treatment of J pasqualei and Joyeuxiella fuhrmanni in cats (as praziquantel/eprinomectin/fipronil/methoprene topical). In India, the same praziquantel dosage/combination product is also approved for treatment of Diplopylidium spp in cats.
Praziquantel at 7.5 mg/kg, PO, for 2 consecutive days is effective against Diphyllobothrium sp in dogs. If this does not eliminate the infection, a single dose of 35 mg/kg, PO, should be administered. A single dose of 35 mg/kg, PO, eliminates Diphyllobothrium latum from infected cats.1 All treatments are extra-label.
Infections with Spirometra sp in dogs and cats can be treated with praziquantel at 7.5 mg/kg, PO or SC, for 2 consecutive days. Spirometra sp infections in dogs and cats can also be treated with praziquantel at 25 mg/kg, PO, daily for two consecutive days. All these treatments are extra-label.
In 2018, resistance to praziquantel and epsiprantel at approved dosages was described in D caninum in multiple US states. Infections were eliminated using nitroscanate or pyrantel/praziquantel/oxantel at approved dosages.
Prevention of Tapeworms in Dogs and Cats
For dogs and cats at high risk of developing intestinal infections with Taenia spp, praziquantel may be administered at the approved dosage every 3–6 months as a preventive. In regions where E granulosus sensu lato is a concern, dogs at risk of developing intestinal infections (eg, by ingestion of internal organs of ruminants) can be treated every 6 weeks with praziquantel at the approved dosage to prevent shedding of eggs in the environment. In regions where E multilocularis is a concern, dogs at risk of developing an intestinal infection (ie, by ingestion of infected rodents) can be treated every 4 weeks with praziquantel at the approved dosage to eliminate the public health concern. High-risk cats can be treated similarly. However, the risk of human infection from infected cats is considered much less than with infected dogs.
References
AAVP and Sakamoto T. 1977. The anthelmintic efficacy of Droncit on adult tapeworms of Hydatigerataeniaeformis, Mesocestoidescorti, Echinococcusmultilocularis, Diphyllobothriumerinacei, and D. latum. Vet Med Rev 1:64–74.
For More Information
Deplazes P, Eckert J, Mathis A, von Samson-Himmelstjerna G, Zahner H. 9.3 Class Cestoda (tapeworms). In: Parasitology in Veterinary Medicine. Wageningen Academic Publishers; 2016:206–253.
Bowman DD. Class Cestoidea. In: Georgis’ Parasitology for Veterinarians. Elsevier;2021:151–170.
Bowman DD, Hendrix CM, Lindsay DS, Barr SC. The Cestodes. In: Feline Clinical Parasitology. Iowa State University Press; 2002:183–231.
Adolph CB, Peregrine AS. Tapeworms. In: Sykes J, ed. Greene’s Infectious Diseases of the Dog and Cat. 5th ed. Elsevier; 2022.
