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* This is the Veterinary Version. *

Tapeworms in Dogs and Cats

(Cestodes)

By Andrew S. Peregrine, BVMS, PhD, DVM, DEVPC, DACVM, Associate Professor, Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada

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.

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, 30–150 rostellar hooks of rose-thorn shape in 3 or 4 circles; large hooks 12–15 μm, smallest 5–6 μm long. Segments shaped like cucumber seeds, with pore near middle of each lateral margin.

Probably most common tapeworm of dogs and cats; cosmopolitan. Occasionally infects people, 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, 26–52 rostellar hooks in double row; large hooks 380–420 μm, small hooks 250–270 μm long. No neck. Sacculate lateral branches of uterus difficult to count.

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, ~34–48 rostellar hooks in double row; large hooks 225–290 μm, small hooks 132–177 μm long. Each side of gravid uterus has 5–10 lateral branches.

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; ~26–44 rostellar hooks in double row; large hooks 170–220 μm, small hooks 110–160 μm long. Each side of gravid uterus 5–10 lateral branches.

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 spp

People, 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 various other states of the USA, Siberia, and other areas

See text for extra-label treatment

Echinococcus granulosus

Dog, wolf, coyote, fox, and several other wild carnivores

Sheep, goats, cattle, pigs, horses, deer, moose, some rodents, occasionally people and other animals; commonly in liver and lungs, occasionally in other organs and tissues

Strobila 2–6 mm long with 3–5 segments; 28–50 (usually 30–36) rostellar hooks in double row; large hooks 27–40 μm, small hooks 21–25 μm long.

Foci among North American range sheep and dogs associating with them; sylvatic moose-wolf cycle where these animals are found; probably cosmopolitan

Dogs: praziquantel

Echinococcus multilocularis

Arctic, red, and gray foxes; coyote, cat, dog

Microtine rodents, occasionally in people; in the liver and other organs

Strobila 1.2–2.7 mm long with 2–4 segments; 26–36 rostellar hooks in double row; large hooks 23–29 μm, small hooks 19–26 μm long.

Central and eastern Europe, former USSR, Alaska, and midwestern USA and Canada; thus far, significant cycle in cats and dogs in North America not recognized. However, multiple cases of alveolar echinococcosis have been diagnosed in dogs across Canada.

Dogs and cats: praziquantel

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 of various mammals, birds, and reptiles; tetrathyridia in intestine of dogs may enter abdomen through intestinal wall.

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 midwest and west; in wild animals elsewhere in USA and Canada

Dogs: praziquantel

Taenia multiceps

Dog, coyote, fox, wolf

Sheep, goats, and other domestic or wild ruminants, rarely people; usually in brain or spinal cord

Strobila 40–100 cm long and up to 5 mm wide. Scolex with 4 suckers and 22–32 hooks in double row; large hooks 150–170 μm, small hooks 90–130 μm long. Vagina with reflexed curve near lateral excretory canal; 9–26 lateral branches on gravid uterus.

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 people; in subcutaneous connective tissue or retroperitoneally

Strobila 20–72 cm long and 3–5 mm wide; 26–32 hooks in double row; large hooks 110–175 μm, small hooks 68–120 μm long. Vagina with reflexed curve near lateral excretory canal; 20–25 lateral branches on gravid uterus.

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 people; subcutaneous and in body cavities

Strobila 70–170 mm long and 1–2 mm wide. Scolex with 30–36 hooks in double row; large hooks 158–187 μm, small hooks 119–141 μm long. Uterus has 16–21 lateral branches, sometimes becoming diffuse.

Reported from Canada and northern USA, 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 26–36 hooks in double row; large hooks 146–195 μm, small hooks 85–141 μm long. Gravid uterus has 18–24 straight and narrow lateral branches.

Reported from Canada and northern USA, 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 32–38 hooks in double row; large hooks 170–191 μm, small hooks 111–127 μm long. Gravid uterus has 20–25 lateral branches. Vagina crosses ovary on poral side of segment.

Reported from western and central Canada and the southern USA

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.

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).

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

People only

Cysticercus “beef measles”

9 × 5 mm

Cattle

Skeletal and cardiac muscle

Taenia solium

People only

Cysticercus “pork measles”

6–10 × 5–10 mm

Pigs, rarely dogs (people may be both definitive and intermediate hosts)

Skeletal and cardiac muscle, occasionally nervous system

Diphyllobothrium spp

People, 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

Dogs, wolves, foxes, and several other wild carnivores

Hydatid cyst

Diameter 50–100 mm, sometimes ≥150 mm

Sheep, cattle, pigs, horses, moose, deer; occasionally people

Commonly in liver and lungs, occasionally in other organs and tissues

Echinococcus multilocularis

Canids and domestic cats

Alveolar hydatid cyst

Variable, penetrates like neoplastic tissue

Field mice, voles, lemmings, sometimes domestic mammals and people

Usually liver, various other organs and tissues

a Human infections with the metacestodes of Taenia crassiceps, T 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.

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.

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* This is the Veterinary Version. *