Merck Manual

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Cestodes of Dogs and Cats in 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.