Marty
12-23-2007, 05:09 PM
Holly Nash, DVM, MS
Veterinary Services Department, Drs. Foster & Smith, Inc.
Tapeworms are flat worms that are segmented. They consist of a head, neck, and then a number of segments. The head usually has suckers or muscular grooves that enable the tapeworm to attach itself to the animal's intestine.
Each tapeworm segment has its own reproductive organs. New segments are continually formed in the neck region of the worm while those at the end of the tapeworm are cast off as they mature. These mature segments contain large numbers of eggs which are often grouped into packets. The segments may often be seen near the anus of the dog or cat. These segments may move if recently passed or, if dried, they look like grains of uncooked rice or cucumber seeds. Tapeworm infections are usually diagnosed by finding these segments on the animal.
Tapeworms of dogs and cats all have life cycles that include an intermediate host. These hosts include fleas, fish, and domestic animals such as sheep and pigs. All of the adult forms of these tapeworms live in the cat's or dog's digestive system. It is interesting that tapeworms have no digestive systems themselves, but absorb nutrients through their skin.
The most common tapeworms that infect dogs and cats are:
Dipylidium caninum
Taenia species
Echinococcus granulosus and E. multiocularis
Diphyllobothrium latum
Spirometra mansonoides
DIPYLIDIUM CANINUM (FLEA TAPEWORM, DOUBLE-PORED TAPEWORM, CUCUMBER SEED TAPEWORM, COMMON DOG TAPEWORM)
The adult form of D. caninum lives in dogs, cats, fox, and occasionally humans. It is found throughout the world. The intermediate host is the flea or louse.
What is the life cycle of D. caninum?
The adult worm, which can be up to 20 inches long, lives in the small intestine. The segments, full of eggs, are passed in the feces. While warm, the segments are active, but as they dry, they break open and liberate the eggs inside. Either an adult louse or a flea larva ingests the eggs. The egg develops into an immature form in the insect. When a dog or cat eats the insect, the immature form develops into an adult and the life cycle is completed.
How is an infection with D. caninum diagnosed?
The diagnosis of a D. caninum infection can be diagnosed by finding the moving segments, dried segments, and occasionally by seeing eggs in the feces if the segment had ruptured.
What are the signs of a D. caninum infection?
In heavy infections, we may notice abdominal discomfort or nervousness in the animal. The animal may vomit and sometimes have convulsions. It is thought that the convulsions are due to toxins produced by the tapeworm. The active segments around the anal area may cause an animal to lick or 'scoot' on the floor.
What signs of infection do we see in humans?
Usually, it is children who become infected with this tapeworm by ingesting flea larvae or adult lice. In general, we rarely see symptoms in humans. In severe infections, abdominal discomfort, diarrhea, and pruritus (itching) in the perianal area may be present.
How do we treat and prevent infections with D. caninum in dogs and cats?
The most common treatment is praziquantel which is found in Droncit and Tradewinds Tapeworm Tabs. The dose is determined by number of tablets per body weight. It can not be used in pregnant animals. The drug epsiprantel (Cestex) is also effective, but cannot be used in puppies and kittens less than 7 weeks of age. For more information see the table on Treatments of Gastrointestinal Parasites at the end of this article.
The most important preventive measures are flea control and lice control. Numerous products are on the market which can be used for this purpose. It is recommended to not only treat the animals but also the environment in an attempt to kill as many flea larvae as possible.
TAENIA SPECIES
There are 9 major species of Taenia tapeworms in North America, 7 of which have dogs or cats as the definitive hosts (animals which harbor the adult form of the parasite).
Latin Name Common Name Definitive Host Intermediate Host
T. saginata Unarmed tapeworm; beef tapeworm Man Cattle
T. solium Armed tapeworm, pork bladderworm Man Pig
T. hydatigena Thin-necked bladderworm Dog, Bear Sheep, goats, cattle, pig, deer
T. krabbei Dog Reindeer
T. multiceps
(Also known as Multiceps multiceps)
Dog
Sheep
T. ovis Dog Sheep, goats
T. pisiformis Dog Rabbit, rodent
T. serialis
(Also known as Multiceps serialis)
Bladderworm Dog Rabbit, hare
T. taeniaeformis Feline tapeworm Cat Rodent
Are the life cycles of the different Taenia species similar?
Yes. The gravid segments of the worm pass out with the feces of the dog or cat. Often, eggs are released from the segments before they are passed. The intermediate host ingests the eggs which are immediately infective. In the intermediate host, the embryo is released in the small intestine and the immature form migrates through the body to various organs, depending on the species of Taenia. The immature form develops a small, fluid-filled sac called a bladder, which surrounds it and provides nourishment. When the 'bladder' is ingested by the definitive host, the head of the tapeworm is released, attaches itself to the intestinal wall, grows, and segments.
Dogs and cats may remain infected for a year or more, and the tapeworms can grow to be over 6 feet long.
What are the signs and symptoms of Taenia infection?
Even in severe infections, there is little evidence of infection other than pruritus around the anal area and finding the segments attached to the animal's fur. Rarely, intestinal obstruction may occur. In general, the intermediate host shows many more signs of illness than the definitive host.
How is an infection with Taenia species diagnosed?
Because the eggs are often released from the segments before the segments pass out through the feces, the main method of diagnosis is through microscopic fecal examination. All Taenia eggs look alike and are identical to those of Echinococcus.
How is a Taenia infection treated and prevented?
Taenia spp. are more susceptible to antihelmintics than other tapeworms. Effective treatments include Drontal Plus and Cestex. For more information see the table on Treatments of Gastrointestinal Parasites at the end of this article.
For more information see the table on Treatments of Gastrointestinal Parasites at the end of this article.
Prevention methods must be based on prohibiting dogs and cats from eating raw meat or offal, and preying on wild animals. The immature forms in the intermediate hosts are killed by freezing or cooking. Rodent control is important.
ECHINOCOCCUS GRANULOSUS, E. MULTIOCULARIS (HYDATID TAPEWORM)
Dogs and wild canids serve as the definitive hosts of Echinococcus granulosus. Herbivores such as sheep are the intermediate hosts. Fox, cats, and dogs are definitive hosts for E. multiocularis, and voles, lemmings, and shrews serve as the intermediate hosts. Humans can also serve as intermediate hosts for both species of Echinococcus. The infection in humans causes a severe, sometimes fatal disease called 'hydatid disease' or echinococcosis.
Both of these tapeworms are found in limited areas in North America. E. granulosus is more common in geographical areas with large numbers of sheep, but is still quite rare. Originally, E. multiocularis was only found in the northern states; more recently it has been found as far south as Illinois, Indiana, and Ohio.
What is the life cycle of Echinococcus tapeworms?
The intermediate host ingests the Echinococcus eggs which are passed in the feces of the definitive host. The eggs hatch and the immature forms penetrate the intestinal wall of the intermediate host and migrate to various organs, usually the lung and liver. Large cysts, 2-5 inches in diameter, develop and contain thousands of infective forms, called 'hydatid sand.'
When the cysts are ingested by a definitive host, each of the infective forms contained in the cyst can develop into an adult tapeworm which are usually less than 7 mm long. The adult worms attach themselves to the small intestine and may live there up to two years.
What are the signs of Echinococcus infections in animals?
As with Taenia tapeworms, the definitive hosts rarely show signs of disease unless the tapeworms are present in high numbers. Usually, the intermediate hosts do not show signs of infection either.
Veterinary Services Department, Drs. Foster & Smith, Inc.
Tapeworms are flat worms that are segmented. They consist of a head, neck, and then a number of segments. The head usually has suckers or muscular grooves that enable the tapeworm to attach itself to the animal's intestine.
Each tapeworm segment has its own reproductive organs. New segments are continually formed in the neck region of the worm while those at the end of the tapeworm are cast off as they mature. These mature segments contain large numbers of eggs which are often grouped into packets. The segments may often be seen near the anus of the dog or cat. These segments may move if recently passed or, if dried, they look like grains of uncooked rice or cucumber seeds. Tapeworm infections are usually diagnosed by finding these segments on the animal.
Tapeworms of dogs and cats all have life cycles that include an intermediate host. These hosts include fleas, fish, and domestic animals such as sheep and pigs. All of the adult forms of these tapeworms live in the cat's or dog's digestive system. It is interesting that tapeworms have no digestive systems themselves, but absorb nutrients through their skin.
The most common tapeworms that infect dogs and cats are:
Dipylidium caninum
Taenia species
Echinococcus granulosus and E. multiocularis
Diphyllobothrium latum
Spirometra mansonoides
DIPYLIDIUM CANINUM (FLEA TAPEWORM, DOUBLE-PORED TAPEWORM, CUCUMBER SEED TAPEWORM, COMMON DOG TAPEWORM)
The adult form of D. caninum lives in dogs, cats, fox, and occasionally humans. It is found throughout the world. The intermediate host is the flea or louse.
What is the life cycle of D. caninum?
The adult worm, which can be up to 20 inches long, lives in the small intestine. The segments, full of eggs, are passed in the feces. While warm, the segments are active, but as they dry, they break open and liberate the eggs inside. Either an adult louse or a flea larva ingests the eggs. The egg develops into an immature form in the insect. When a dog or cat eats the insect, the immature form develops into an adult and the life cycle is completed.
How is an infection with D. caninum diagnosed?
The diagnosis of a D. caninum infection can be diagnosed by finding the moving segments, dried segments, and occasionally by seeing eggs in the feces if the segment had ruptured.
What are the signs of a D. caninum infection?
In heavy infections, we may notice abdominal discomfort or nervousness in the animal. The animal may vomit and sometimes have convulsions. It is thought that the convulsions are due to toxins produced by the tapeworm. The active segments around the anal area may cause an animal to lick or 'scoot' on the floor.
What signs of infection do we see in humans?
Usually, it is children who become infected with this tapeworm by ingesting flea larvae or adult lice. In general, we rarely see symptoms in humans. In severe infections, abdominal discomfort, diarrhea, and pruritus (itching) in the perianal area may be present.
How do we treat and prevent infections with D. caninum in dogs and cats?
The most common treatment is praziquantel which is found in Droncit and Tradewinds Tapeworm Tabs. The dose is determined by number of tablets per body weight. It can not be used in pregnant animals. The drug epsiprantel (Cestex) is also effective, but cannot be used in puppies and kittens less than 7 weeks of age. For more information see the table on Treatments of Gastrointestinal Parasites at the end of this article.
The most important preventive measures are flea control and lice control. Numerous products are on the market which can be used for this purpose. It is recommended to not only treat the animals but also the environment in an attempt to kill as many flea larvae as possible.
TAENIA SPECIES
There are 9 major species of Taenia tapeworms in North America, 7 of which have dogs or cats as the definitive hosts (animals which harbor the adult form of the parasite).
Latin Name Common Name Definitive Host Intermediate Host
T. saginata Unarmed tapeworm; beef tapeworm Man Cattle
T. solium Armed tapeworm, pork bladderworm Man Pig
T. hydatigena Thin-necked bladderworm Dog, Bear Sheep, goats, cattle, pig, deer
T. krabbei Dog Reindeer
T. multiceps
(Also known as Multiceps multiceps)
Dog
Sheep
T. ovis Dog Sheep, goats
T. pisiformis Dog Rabbit, rodent
T. serialis
(Also known as Multiceps serialis)
Bladderworm Dog Rabbit, hare
T. taeniaeformis Feline tapeworm Cat Rodent
Are the life cycles of the different Taenia species similar?
Yes. The gravid segments of the worm pass out with the feces of the dog or cat. Often, eggs are released from the segments before they are passed. The intermediate host ingests the eggs which are immediately infective. In the intermediate host, the embryo is released in the small intestine and the immature form migrates through the body to various organs, depending on the species of Taenia. The immature form develops a small, fluid-filled sac called a bladder, which surrounds it and provides nourishment. When the 'bladder' is ingested by the definitive host, the head of the tapeworm is released, attaches itself to the intestinal wall, grows, and segments.
Dogs and cats may remain infected for a year or more, and the tapeworms can grow to be over 6 feet long.
What are the signs and symptoms of Taenia infection?
Even in severe infections, there is little evidence of infection other than pruritus around the anal area and finding the segments attached to the animal's fur. Rarely, intestinal obstruction may occur. In general, the intermediate host shows many more signs of illness than the definitive host.
How is an infection with Taenia species diagnosed?
Because the eggs are often released from the segments before the segments pass out through the feces, the main method of diagnosis is through microscopic fecal examination. All Taenia eggs look alike and are identical to those of Echinococcus.
How is a Taenia infection treated and prevented?
Taenia spp. are more susceptible to antihelmintics than other tapeworms. Effective treatments include Drontal Plus and Cestex. For more information see the table on Treatments of Gastrointestinal Parasites at the end of this article.
For more information see the table on Treatments of Gastrointestinal Parasites at the end of this article.
Prevention methods must be based on prohibiting dogs and cats from eating raw meat or offal, and preying on wild animals. The immature forms in the intermediate hosts are killed by freezing or cooking. Rodent control is important.
ECHINOCOCCUS GRANULOSUS, E. MULTIOCULARIS (HYDATID TAPEWORM)
Dogs and wild canids serve as the definitive hosts of Echinococcus granulosus. Herbivores such as sheep are the intermediate hosts. Fox, cats, and dogs are definitive hosts for E. multiocularis, and voles, lemmings, and shrews serve as the intermediate hosts. Humans can also serve as intermediate hosts for both species of Echinococcus. The infection in humans causes a severe, sometimes fatal disease called 'hydatid disease' or echinococcosis.
Both of these tapeworms are found in limited areas in North America. E. granulosus is more common in geographical areas with large numbers of sheep, but is still quite rare. Originally, E. multiocularis was only found in the northern states; more recently it has been found as far south as Illinois, Indiana, and Ohio.
What is the life cycle of Echinococcus tapeworms?
The intermediate host ingests the Echinococcus eggs which are passed in the feces of the definitive host. The eggs hatch and the immature forms penetrate the intestinal wall of the intermediate host and migrate to various organs, usually the lung and liver. Large cysts, 2-5 inches in diameter, develop and contain thousands of infective forms, called 'hydatid sand.'
When the cysts are ingested by a definitive host, each of the infective forms contained in the cyst can develop into an adult tapeworm which are usually less than 7 mm long. The adult worms attach themselves to the small intestine and may live there up to two years.
What are the signs of Echinococcus infections in animals?
As with Taenia tapeworms, the definitive hosts rarely show signs of disease unless the tapeworms are present in high numbers. Usually, the intermediate hosts do not show signs of infection either.