Taenia spp.
Species
Species
Canine
Taenia crassiceps
Taenia hydatigena
Taenia multiceps
Taenia pisiformis
Taenia serialis
Feline
Taenia taeniaeformis
Overview of Life Cycle
Taenia spp. are cyclophyllidean cestodes with indirect life cycles that require specific intermediate hosts. Dogs and cats infected with adult cyclophyllidean tapeworms shed egg-laden proglottids in their feces. When the appropriate vertebrate intermediate host consumes the eggs, larval cysts develop. Dogs and cats are infected when they ingest these larval cysts while preying on or scavenging infected vertebrates.
Stages
- Taenia spp. eggs contain an embryo with six hooks (hexacanth embryo) and are morphologically indistinguishable from those of Echinococcus spp.
- Examples of metacestodes of Taenia spp. in the intermediate host include:
- cysticercus, a small, bladder-like cyst
- coenurus, a large, bladder-like cyst
- strobilocercus, a more developed form of a cysticercus
Metacestodes and intermediate hosts of selected Taenia spp.
T. crassiceps
- Definitive Host: Dog
- Metacestode: Cysticercus
- Intermediate Host: Rodents
- Location in Intermediate Host: Viscera
T. hydatigena
- Definitive Host: Dog
- Metacestode: Cysticercus
- Intermediate Host: Wild ruminants, horses, and pigs
- Location in Intermediate Host: Viscera
T. multiceps
- Definitive Host: Dog
- Metacestode: Coenurus
- Intermediate Host: Sheep
- Location in Intermediate Host: Brain and spinal cord
T. pisiformis
- Definitive Host: Dog
- Metacestode: Cysticercus
- Intermediate Host: Rabbits
- Location in Intermediate Host: Viscera
T. serialis
- Definitive Host: Dog
- Metacestode: Coenurus
- Intermediate Host: Rabbits and Rodents
- Location in Intermediate Host: Subcutaneous and intramuscular connective tissue
T. taeniaeformis
- Definitive Host: Cat
- Metacestode: Strobilocercus
- Intermediate Host: Rodents
- Location in Intermediate Host: Liver
- Adult Taenia species are found in the small intestine of an infected dog or cat.
- The scolex of the Taenia species common in dogs and cats in North America has two rows of hooks for attachment to the small intestine mucosa.
- Proglottids are shed in the feces of an infected dog or cat. When proglottids rupture, eggs may be shed.
Disease
Disease in dogs and cats due to infection with adult Taenia species is rare.
Passage of proglottids may be associated with perianal irritation.
Occasional intestinal impactions with Taenia spp. necessitating surgical removal of a mass of tapeworms from the small intestine have been reported.
Rare reports of aberrant infection with metacestodes of Taenia spp. leading to severe disease in dogs and cats also exist.
Prevalence
Taenia species are commonly found in cats and dogs throughout North America.
A number of factors influence the likelihood that a dog or cat will be infected with tapeworms, including the geographic region and the opportunity the animal may have to ingest an infected intermediate host.
Prevalence data generated by fecal flotation alone almost certainly underestimate the frequency of infection because proglottids (and thus eggs) are focally distributed in fecal material; a given fecal sample may be negative for tapeworm proglottids or eggs, even in the presence of an infection.
Host Associations and Transmission Between Hosts
- Adults of Taenia pisiformis are known to infect only dogs and wild canids. Infection of dogs occurs following ingestion of cysticerci in rabbit tissue.
- Adults of Taenia taeniaeformis infect only cats and wild felids and are acquired by ingestion of strobilocerci in infected rodents.
- Other Taenia species are considered less common in domestic cats and dogs in North America although they are occasionally reported (see Stages)
- In the absence of predation or opportunities for scavenging, infection with Taenia spp. will not occur.
Prepatent Period and Environmental Factors
Dogs begin shedding proglottids of T. pisiformis between 1.5-2 months following infection
Cats can begin shedding proglottids of T. taeniaeformis at 1 month post-infection, but the prepatent period may be as long as 3 months.
Eggs can remain viable for up to a year in ideal conditions, low temperature and high humidity, but are susceptible to desiccation under high temperature/ low humidity conditions. Under harsh conditions, eggs may only persist in the environment for 1 week.
In the absence of treatment, adult Taenia taeniaeformis survive in the small intestine of the cat definitive host for as long as 34 months.
Site of Infection and Pathogenesis
Taenia spp. typically do not cause significant disease in dogs and cats, but because they are aesthetically unpleasant, treatment is warranted.
Intestinal impactions requiring surgery have been reported due to T. taeniaeformis in cats. Cats with this condition present with clinical and radiographic signs similar to a linear foreign body.
Diagnosis
- Diagnosis of infection is reached by identifying proglottids in the fecal material, eggs on fecal flotation, or PCR.
- Because proglottids are not uniformly distributed in the fecal material and eggs do not consistently float, fecal flotation alone is not a reliable means of diagnosing tapeworm infections in dogs and cats.
- Proglottids of Taenia spp. have a characteristic rectangular shape with a single, lateral genital pore.
- Taenia species eggs are 25-40 μm in diameter and are brown with a thick, striated shell wall. The developing embryo has 6 hooks.
- Taenia eggs cannot be distinguished from Echinococcus eggs via microscopic examination alone.
Treatment
Praziquantel and epsiprantel are approved for the treatment of Taenia spp. infections in dogs and cats. Febendazole is also approved for the treatment of Taenia pisiformis in dogs.
For dogs, praziquantel is formulated with some heartworm preventives to provide broad-spectrum internal parasite control. For cats, praziquantel is formulated with emodepside to provide broad-spectrum internal parasite control.
Treatment of Taenia spp. in dogs and cats must be combined with management changes to prevent ingestion of vertebrate prey species; in the absence of these changes, re-infection is likely to occur.
Control and Prevention
In dogs that are allowed outside or that are known to have predatory behavior, a heartworm preventive containing praziquantel will routinely treat infections with Taenia spp. and other cyclophyllidean cestodes.
Prevention of predation and scavenging activity by keeping cats indoors and dogs confined to a leash or in a fenced yard will limit the opportunity for dogs and cats to acquire infection with Taenia spp.
Public Health Considerations
Isolated reports of zoonotic infection with larval Taenia spp. of dogs and cats exist. However, the overall risk of human infection with Taenia spp. in North America appears extremely low.
Other Taenia species of significant public health concern include T. saginata and T. solium, but neither are parasites of domestic cats and dogs. Humans become infected via the ingestion of cysticerci in beef or pork, respectively.
Selected References
Conboy G. Cestodes of dogs and cats in North America. Vet Clin North Am Small Anim Pract 39:1075-1090, 2009.
Raether W, Hänel H. Epidemiology, clinical manifestations and diagnosis of zoonotic cestode infections: an update. Parasitol Res 91:412-438, 2003.
Wilcox RS, Bowman DD, Barr SC, et al. Intestinal obstruction caused by Taenia taeniaeformis infection in a cat. JAAHA 45:93-6, 2009.
Species
Species
Canine
Taenia crassiceps
Taenia hydatigena
Taenia multiceps
Taenia pisiformis
Taenia serialis
Feline
Taenia taeniaeformis
Overview of Life Cycle
Taenia spp. are cyclophyllidean cestodes with indirect life cycles that require specific intermediate hosts. Dogs and cats infected with adult cyclophyllidean tapeworms shed egg-laden proglottids in their feces. When the appropriate vertebrate intermediate host consumes the eggs, larval cysts develop. Dogs and cats are infected when they ingest these larval cysts while preying on or scavenging infected vertebrates.
Stages
- Taenia spp. eggs contain an embryo with six hooks (hexacanth embryo) and are morphologically indistinguishable from those of Echinococcus spp.
- Examples of metacestodes of Taenia spp. in the intermediate host include:
- cysticercus, a small, bladder-like cyst
- coenurus, a large, bladder-like cyst
- strobilocercus, a more developed form of a cysticercus
Metacestodes and intermediate hosts of selected Taenia spp.
T. crassiceps
- Definitive Host: Dog
- Metacestode: Cysticercus
- Intermediate Host: Rodents
- Location in Intermediate Host: Viscera
T. hydatigena
- Definitive Host: Dog
- Metacestode: Cysticercus
- Intermediate Host: Wild ruminants, horses, and pigs
- Location in Intermediate Host: Viscera
T. multiceps
- Definitive Host: Dog
- Metacestode: Coenurus
- Intermediate Host: Sheep
- Location in Intermediate Host: Brain and spinal cord
T. pisiformis
- Definitive Host: Dog
- Metacestode: Cysticercus
- Intermediate Host: Rabbits
- Location in Intermediate Host: Viscera
T. serialis
- Definitive Host: Dog
- Metacestode: Coenurus
- Intermediate Host: Rabbits and Rodents
- Location in Intermediate Host: Subcutaneous and intramuscular connective tissue
T. taeniaeformis
- Definitive Host: Cat
- Metacestode: Strobilocercus
- Intermediate Host: Rodents
- Location in Intermediate Host: Liver
- Adult Taenia species are found in the small intestine of an infected dog or cat.
- The scolex of the Taenia species common in dogs and cats in North America has two rows of hooks for attachment to the small intestine mucosa.
- Proglottids are shed in the feces of an infected dog or cat. When proglottids rupture, eggs may be shed.
Disease
Disease in dogs and cats due to infection with adult Taenia species is rare.
Passage of proglottids may be associated with perianal irritation.
Occasional intestinal impactions with Taenia spp. necessitating surgical removal of a mass of tapeworms from the small intestine have been reported.
Rare reports of aberrant infection with metacestodes of Taenia spp. leading to severe disease in dogs and cats also exist.
Prevalence
Taenia species are commonly found in cats and dogs throughout North America.
A number of factors influence the likelihood that a dog or cat will be infected with tapeworms, including the geographic region and the opportunity the animal may have to ingest an infected intermediate host.
Prevalence data generated by fecal flotation alone almost certainly underestimate the frequency of infection because proglottids (and thus eggs) are focally distributed in fecal material; a given fecal sample may be negative for tapeworm proglottids or eggs, even in the presence of an infection.
Host Associations and Transmission Between Hosts
- Adults of Taenia pisiformis are known to infect only dogs and wild canids. Infection of dogs occurs following ingestion of cysticerci in rabbit tissue.
- Adults of Taenia taeniaeformis infect only cats and wild felids and are acquired by ingestion of strobilocerci in infected rodents.
- Other Taenia species are considered less common in domestic cats and dogs in North America although they are occasionally reported (see Stages)
- In the absence of predation or opportunities for scavenging, infection with Taenia spp. will not occur.
Prepatent Period and Environmental Factors
Dogs begin shedding proglottids of T. pisiformis between 1.5-2 months following infection
Cats can begin shedding proglottids of T. taeniaeformis at 1 month post-infection, but the prepatent period may be as long as 3 months.
Eggs can remain viable for up to a year in ideal conditions, low temperature and high humidity, but are susceptible to desiccation under high temperature/ low humidity conditions. Under harsh conditions, eggs may only persist in the environment for 1 week.
In the absence of treatment, adult Taenia taeniaeformis survive in the small intestine of the cat definitive host for as long as 34 months.
Site of Infection and Pathogenesis
Taenia spp. typically do not cause significant disease in dogs and cats, but because they are aesthetically unpleasant, treatment is warranted.
Intestinal impactions requiring surgery have been reported due to T. taeniaeformis in cats. Cats with this condition present with clinical and radiographic signs similar to a linear foreign body.
Diagnosis
- Diagnosis of infection is reached by identifying proglottids in the fecal material, eggs on fecal flotation, or PCR.
- Because proglottids are not uniformly distributed in the fecal material and eggs do not consistently float, fecal flotation alone is not a reliable means of diagnosing tapeworm infections in dogs and cats.
- Proglottids of Taenia spp. have a characteristic rectangular shape with a single, lateral genital pore.
- Taenia species eggs are 25-40 μm in diameter and are brown with a thick, striated shell wall. The developing embryo has 6 hooks.
- Taenia eggs cannot be distinguished from Echinococcus eggs via microscopic examination alone.
Treatment
Praziquantel and epsiprantel are approved for the treatment of Taenia spp. infections in dogs and cats. Febendazole is also approved for the treatment of Taenia pisiformis in dogs.
For dogs, praziquantel is formulated with some heartworm preventives to provide broad-spectrum internal parasite control. For cats, praziquantel is formulated with emodepside to provide broad-spectrum internal parasite control.
Treatment of Taenia spp. in dogs and cats must be combined with management changes to prevent ingestion of vertebrate prey species; in the absence of these changes, re-infection is likely to occur.
Control and Prevention
In dogs that are allowed outside or that are known to have predatory behavior, a heartworm preventive containing praziquantel will routinely treat infections with Taenia spp. and other cyclophyllidean cestodes.
Prevention of predation and scavenging activity by keeping cats indoors and dogs confined to a leash or in a fenced yard will limit the opportunity for dogs and cats to acquire infection with Taenia spp.
Public Health Considerations
Isolated reports of zoonotic infection with larval Taenia spp. of dogs and cats exist. However, the overall risk of human infection with Taenia spp. in North America appears extremely low.
Other Taenia species of significant public health concern include T. saginata and T. solium, but neither are parasites of domestic cats and dogs. Humans become infected via the ingestion of cysticerci in beef or pork, respectively.
Selected References
Conboy G. Cestodes of dogs and cats in North America. Vet Clin North Am Small Anim Pract 39:1075-1090, 2009.
Raether W, Hänel H. Epidemiology, clinical manifestations and diagnosis of zoonotic cestode infections: an update. Parasitol Res 91:412-438, 2003.
Wilcox RS, Bowman DD, Barr SC, et al. Intestinal obstruction caused by Taenia taeniaeformis infection in a cat. JAAHA 45:93-6, 2009.