Tapeworms

Introduction:

Tapeworms can infect virtually any animal including dogs, cats and humans. For this reason, meat is inspected for infection prior to consumption approval. The most common tapeworm Dipylidium caninum are more concerning to the pet owner than they are harmful.¹ There are 4 species found in dogs and/or cats: Dipylidium caninum, Taenia pisiformis, Echinococcus granulosus, and Echinococcus multilocularis.^2,3 An intermediate host is required for all tapeworm infections.

Geographic region and opportunity for the pet to ingest an infected intermediate host influence the likelihood that a dog or cat will become infected with tapeworms. Tapeworm infections are underestimated in the pet population. D. caninum and Taenia spp are found throughout North America while Echinococcus spp. are limited to north-central, midwestern, and the southwestern United States as well as Canada and Alaska.

Life Cycle:

Tapeworm life cycles require a specific intermediate host.¹ Dogs and cats are infected with Dipylidium caninum by ingesting a flea that contain larval cysts from consuming egg-laden proglottids released to the environment from an active tapeworm infection. The tapeworm D. caninum requires the flea as the intermediate host.  The tapeworms Taenia taeniaeformis and Echinococcus multilocularis in animals require the ingestion of infected rodents, and the tapeworms Echinococcus granulosus and T. pisiformis require ingestion of infected rabbit or sheep tissue. The tapeworm larvae will mature in the small intestine and form segments known as proglottids that contain both male and female reproductive organs. The mature proglottids will be released in the feces or around the perianal area in a dried state resembling grains of rice stuck to the fur. Prepatent period, or time from infection until time of detection, of D. caninum may be as soon as 2 to 3 weeks after ingestion of an infected flea; and the prepatent period of both Echinococcus spp. and Taenia spp. is longer, closer to 1 to 2 months after ingestion of infected animal tissue.

Disease State:

Tapeworms rarely cause significant signs of disease. Perianal irritation from dried proglottids may occur and high number of worms can cause obstruction due to impaction.

Diagnosis:

The fecal flotation test is not a reliable method of detecting tapeworms in dogs and cats. Visualization of tapeworm proglottids on the feces or dried around the pet’s perianal region is the most common way of diagnosing a tapeworm infection.

Treatment:

There are specific products labeled to treat one or more of the mentioned tapeworm infections in dogs and cats. Treatment of tapeworms in dogs and cats must be combined with appropriate management, such as flea control and prevention of ingestion of infected prey. Tapeworm re-infections are likely to occur if fleas are not controlled and scavenging allowed to continue.

Public Health:

Tapeworm infections may pose as a public health risk. Echinococcus spp. zoonotic infections are rare in North America; and there have been isolated reports of zoonotic infection with larval Taenia spp.^2,3 The eggs found inside the proglottids shed in the feces of an infected dog or cat are immediately infectious to the intermediate animal. People who consume infective eggs may develop cysts requiring drainage, surgical removal, and/or extended treatment. In the case of E. multilocularis, it is possible for a hyadid cyst to form where surgery is unlikely to be successful and long-term anthelminthic therapy may be required. D. caninum may require antihelmintic therapy especially in children.

The CAPC website and the website Pets and Parasites by CAPC are reliable resources for additional information regarding tapeworms and your dog.

1. CAPC guidelines: Dipylidium Caninum. Companion Animal Parasite Council. https://www.capcvet.org/guidelines/dipylidium-caninum/ (Accessed 24 August 2018)