Tapeworms in Dogs and Cats

by Chick Newman

Dipylidium caninum.........Taenia species......SEchinococcus.....Spirometra.....Diphyllobothrium...

Introduction:

Tapeworms (cestodes) are multi-segmented flat worms that parasitize the intestine of the definitive host (dog or cat); each segment of the chain is a separate reproductive unit, the proglottid, which if broken from the main body, is capable of independent regrowth into a fully segmented worm (with multiple proglottids). With proglottids attached, the entire chain moves as a single unit, in rhythmic fashion.The tapeworm is anchored to the intestinal lining by one end of the chain via the scolex. The scolex is minute, maybe a less than one millimeter or a few millimeters, in comparison to the entire tapeworm chain which may be a few millimeters to several meters in length. The scolex contains various mouth parts or hooks for attachment.

Reproduction requires an intermediate host for development of tapeworm embryos; at maturation, the intermediate host will eventually contain some form of a cyst with one of more scolexes (each capable of forming a full worm) in one or more tissues; this infected tissue is usually eaten by the definitive host in which the contents of the cyst is released, followed by final development then infestion by the adult tapeworm. In some instances, humans can become an "accidental" intermediate host...with dire consequences (see Echinococcus, below).

Diagnosis of tapeworm infestations may be via recognition of visible proglottids on the perineal skin; however, some tapeworms are very small...only a few millimeters including all segments...and may be missed. Alternatively, visualization of tapeworm eggs with standard fecal flotation methods may be accomplished. Microscopic examination of proglottid segments is useful in identifying the species of tapeworm.

Flea Tapeworm:

Introduction: The flea (Ctenocepalides species) tapeworm is called Dipylidium caninum. Dogs, cats and wild canids and felids are suseptible to infestation. In addition, there are reports of human infestation, principally small children who (playing close to the ground) ingest flea larvae or adults (containing devloping Dipylidium) in the environment, much like dogs or cats (see Life Cycle, below). However, the human flea (Pulex irritans) is also a vector for human infestation. Important point: Infection of pets or humans from direct contact with proglottids is highly unlikely!

Life Cycle: The life cycle of Dipylidium caninum is illustrated on another page The embryonated eggs are consumed by developing (nymph [or adult ] dog louse or) flea larvae (the intermediate host) and develop there until the flea becomes an adult. If the latter is consumed, the flea is digested and the developed form of the tapeworm is released to eventually attach to the intestine and grow (multiple proglottid chain/segments).

Clinical Signs: Light infections do not produce significant clinical signs, except an occasional visible proglottid crawling around the anus or tail (which may affect (i.e. "freak out") the pet owner) . Perianal pruritis (itching) resulting in "butt-dragging" or licking of the affected area is frequently seen. In heavier infestations, diarrhea, flatulence and mild weight loss with an ill-thrifty appearance are possible.

Treatment:

Praziquantel (Droncit®): 5-10 mg/kg as a single dose

Niclosamide (Yomesan® ): 25 mg/kg as a single dose

Bunamidine HCL (Scolaban®) (dog only): 50 mg/kg as a single dose

¥Flea control of the environment and the animal is absolutely essential, or Dipylidium infestation will recur after treatment¥.

Taenia Species:

Introduction: In general, the intermediate host for Taenia species is another vertebrate animal (the "prey"). In dogs, the most common intermediate hosts are rabbits (Taenia pisiformis), sheep (Taenia hydatigena, Taenia mulitceps) and deer and moose (Taenia krabbei). In cats, the most common intermediate host is the rodent (Taenia taeniaeformis).

Life Cycle: Like all tapeworms, there is an intermediate and a definitive host (the dog or cat). For most of the Taenia species, the prepatent period ( time from infection to eggs production) is approximately two months. The general life cycle for the Taenia infestations of the dog is illustrated here.

Clinical Signs: Proglottid may be seen in perineal skin and some pruritis in this area. Heavy infestation with some species (Taenia taeniaformis, Taenia pisiformis) may result in significant diarrhea and even intestinal obstruction. In general, most infestation of dogs with eitherTaenia multiceps, Taenia hydatigena and Taenia krabbei are considered clinically unimportant (these infestations rarely cause a problem)

Treatment:

Taenia taeniaformis (cat tapeworm; rodent intermediate host)

Praziquantel (Droncit®): 2.5-5 mg/kg orally or by subcutaneous injection

Niclosamide (Yomesan® ): 157 mg/kg orally

Fenbendazole (Panacur®  ): 50 mg/kg orally daily for three days.

Mebendazole: 22 mg/kg orally daily for 3-5 days.

Espirantel:  2.8 mg/kg orally

Bunamidine HCl (Scolaban®): 25-50 mg/kg orally or by subcutaneous injection

Taenia pisiformis (rabbit intermediate host)

Praziquantel (Droncit®): 2.5-5 mg/kg orally or by subcutaneous injection

Niclosamide (Yomesan® ): 157 mg/kg orally

Mebendazole: 22 mg/kg orally daily for 3-5 days

Fenbendazole (Panacur®  ): 50 mg/kg orally daily for three days

Espirantel:  5.5 mg/kg orally

Dichlorophene: 220 mg/kg orally

Bunamidine HCl (Scolaban®): 25-50 mg/kg orally or by subcutaneous injection

Taenia multiceps (sheep intermediate host)

Praziquantel (Droncit®): 2.5-5 mg/kg orally or by subcutaneous injection

Niclosamide (Yomesan® ): 157 mg/kg orally

Mebendazole: 22 mg/kg orally daily for 3-5 days

Fenbendazole (Panacur®  ): 50 mg/kg orally

Dichlorophene: 220 mg/kg orally

Bunamidine HCl (Scolaban®): 25-50 mg/kg orally or by subcutaneous injection

Taenia hydatigena (sheep intermediate host)

Praziquantel (Droncit®): 2.5-5 mg/kg orally or by subcutaneous injection

Niclosamide (Yomesan® ): 157 mg/kg orally

Mebendazole: 22 mg/kg orally daily for 3-5 days

Fenbendazole (Panacur®  ): 50 mg/kg orally

Dichlorophene: 220 mg/kg orally

Taenia krabbei (moose and deer intermediate host)

Praziquantel (Droncit®): 2.5-5 mg/kg orally or by subcutaneous injection

Niclosamide (Yomesan® ): 157 mg/kg orally

Mebendazole: 22 mg/kg orally daily for 3-5 days

Fenbendazole (Panacur®  ): 50 mg/kg orally

Dichlorophene: 220 mg/kg orally

Echinococcus:

Introduction: The species, Echinococcus granulosus, is a very tiny...only a few millimeters...tapeworm whose primary host is the dog and other canids and whose intermediate host may be a variety of grazing vertebrates.. The worm consists of just three or four segments, and only the terminal segment is capable of reproduction.. Echinoccus multilocularis is similar in size and appearance and may infect cats and other small vertebrates who hunt rodents, the intermediate hosts. While a rare occurence, humans may become inadvertent intermediate hosts to both E.granulosus and E. multilocularis, resulting in hydatid disease or alveolar hydatid disease, respectively. More about potentially fatal human forms of Echinococcus infestations can be found on this web site as well as many other internet resources, federal and state health offices, etc.

Life Cycle: The life cycle of Echinococcus in the dog illustrated on a separate page. The perpetuation of Echinococcus so that infestation in dogs remains possible is via the wild, or Sylvatic cycle. This describes the continuation of the parasite in the wild via carnivore (e.g. wolf,fox, and their animal prey...).

Clinical Signs: Infestation with Echinococcus produces mild clinical signs in dogs (no signs or mild diarrhea and hydatid disease in intermediate hosts...e.g humans.

Diagnosis: Fecal flotation may reveal tapeworm eggs (these look like eggs from other tapeworm species); history consistent with echinococcosis.

Prevention: A putatively effective vaccination for Echinococcus granulosus has recently been reported in the literature; its efficacy and utility for pet dogs is questionable but if or when it becomes available, in years from now, it may be considered for dogs in regions at higher risk for exposure, in order to protect humans who contact these dogs from hydatid disease.

Treatment of Animals: (treat all dogs is suspicious)

Bunamidine (Scolaban®): 20-50 mg/kg; repeat in 2 days, then in one month

Mebendazole: 22 mg/kg orally daily for 3-5 days

Praziquantel (Droncit®): 25-50 mg/kg orally or by injection (note...this is 2.5-10 times the usual dose used for Taenia and Dipylidium)

Do not feed infected sheep or wild ruminant viscera to dogs!!!

Spirometra:

Introduction: Spirometra infestations of carnivores occur frequently in the southeastern United States. More often in cats, but sometimes dogs are also affected. States in which cases have been reported in cats include, Louisiana, Florida, Georgia, New York, New Jersey, Pennsylvania, South Carolina and Hawaii. Many reported cases are in Florida and the Gulf Coast region most likely because of the rich acquasystems in that area in which the tapeworm must develop (see Life Cycle). A number of cases have been documented in South Carolina and Georgia.

Life Cycle: The life cycle of Spirometra is significantly different from the tapeworms previously mentioned on this page, but similar to Diphyllobothrium latum. Eggs (not segments) are passed in the feces 10-30 days after infestation of the definitive host and, in the presence of water, each hatches into a free swimming form (they have moving "cilia"), the coracidium. When these are consumed by certain species of the genus Cyclops (a crustacean, the first intermediate host), they develop into a wormlike form, the procercoid . If any vertebrate other than the definitive host (carnivore) or a fish consumes the cylops, the procercoid further develops into a plerocercoid larvae in the muscle and connective tissue of the vertebrate (the second intermediate host). Then, when the second intermediate host is consumed by a cat (or wild feline), racoon and, occasionally, a dog the plerocercoid develops into an adult tapeworm in the intestine...up to 1500 cm (about 3.5 feet) in length. And the cycle repeats....

The second intermediate host may also be eaten by another non-fish vertebrate rather than the definitive host; in this instance the plerocercoids migrate through the tissue of the new host but do not develop further. However, this animal is also potentially infective for the definitive host. In other words, if the second intermediate host is consumed, the consuming animal can also serve as an intermediate host. Regardless of which animal harbors the plerocercoids, when consumed by a definitive host, the tapeworm develops into an adult.

Clinical Signs:

In the definitive host, there may be no clinical signs, mild to moderate diarrhea, vomiting, and weight loss.

In the intermediate host, the presence of plerocercoids can result in tissue inflammation, and if migrated to organs, signs of organ inflammation...Sparganosis. Cases of migration to aberrant locations such as the spinal cord, brain, eye and urinary tract have been reported. Infestation with plerocercoids is known as Sparangosis. In some intermediate hosts, the pleroceroids have been shown to actually reproduce asexually and produce a condition known as Proliferative Sparganosis, The dividing plerocercoids grow in organs, causing inflammation, fibrosis and organ failure. This is particularly important because there is potential zoonosis, and humans can become inadvertent intermediate hosts.

Diagnosis:

Fecal Flotation technique, using zinc sulfate solution (as described for Giardia) will reveal eggs whose appearance is markedly different in appearance than the eggs from the other tapeworms discussed thus far. These eggs look similar to the oblong-shaped eggs of flukes, in which there is an "operculum" at one pole

Treatment:

Definitive Host: Standard antihelminthic drugs effective in the treatment of other tapeworms are not effective in the treatment of adult Spirometra! (in the definitive host animal).

Praziquantel (Droncit®): at the standard 2.5-5.0 mg/kg is not effective.

Praziquantel (Droncit®): at 25 mg/kg on two consecutive days may be effective in eliminating this tapeworm from the cat (note...this is 2.5-10 times the usual dose and twice the customary frequency [two consecutive days...instead of once])

Intermediate Host: Medical treatment of Sparaginosis has not been rewarding!!! As this is of zoonotic potential, the absence of an effective treatment is worrisome.

Zoonosis:

Humans can become infected by drinking water containing copepods with infective plerocercoids, ingesting plerocercoids in the flesh of an intermediate host or by migration of plerocercoids into a wound or across a mucus membrane. Manifestation of Spargangosis in humans is sometimes via the appearance of subcutaneous lumps in such sites as the scrotum or breast. Surgical removal is curative, However, on occasion, there is migration to and proliferation of plerocercoids in the brain and spinal cord, or urinary tract producing serious clinical problems, and even death. Proliferative sparangosis has definitely been reported in humans!

Diphyllobothrium

Introduction: Diphyllobothrium are similar to Spirometra tapeworms, discussed above. Both species belong to the taxonomic family, Diphyllobothriidae.

Life Cycle: The life cycle is the same as for Spirometra. When a fish eats another fish, the plerocercoid just invades the muscle of the second (paratenic host...another second intermediate host)...and like before, in the second intermediate host, waits for a definitive (vertebrate) host, such as a dog, cat or human to consume the second intermediate (or paratenic) host animal in which it develops into an adult tapeworm.

Clinical Signs: Infestation in cats and in dogs generally produces mild gastrointestinal signs or no clinical signs. Dogs and cats are, however, then a potential reservoir (though not through direct contact) of infection for humans.

Diagnosis: Eggs are similar to those described for Spirometra...and diagnosis is also via the fecal flotation procedure.

Treatment (Dogs and Cats): generally adult tapeworms are relatively easy to treat

Praziquantel (Droncit®): 7.5 mg/kg orally or subcutaneously once

Treatment (Humans):

Niclosamide (Yomesan®): 2 gm by mouth, once

Praziquantel (Droncit  ): 5-20 mg/kg by mouth, once

Copyright 1997-2012 Newman Veterinary Medical Services, Seattle, WA

 

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