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Tapeworms in Dogs

February 8, 2009

Background

Several species of Tapeworms infect both dogs and cats. The most common species of canine tapeworm is (Dipylidium caninum). Other species of Tapeworms that can infect dogs include Taenia spp. and Echinococcus spp. Tapeworms have relatively complex lifecycle in that they require more than one “host” animal to complete their life cycle. The intermediate host (also known as the primary host) is infected with tapeworm larvae. The final host (or secondary host) becomes infected after eating one of the intermediate hosts. In the intestine of the final host the tapeworm will develop into its adult form. Dogs, being carnivores, tend to be final hosts in the Tapeworm lifecycle. Intermediate hosts for Dipylidium caninum include fleas and lice, which dogs often ingest as they are grooming themselves. This is one of the reasons why it is so important to treat your dog for fleas regularly.

Lifecycle

The adult Tapeworm lives in the small intestine of dogs and cats. It sucks onto the wall of the small intestine with its mouth, whilst its tail end is free to move around in the intestinal lumen. The tapeworm regularly sheds segments from its tail end which are around 5-8mm in length. These segments can be found in an infected dog’s faeces or sometimes “crawling” around the anal region. Segments can emerge from your dog’s anus whilst your dog is sitting or lying around in the house, it is by no means a purely outdoors thing! Segments of Tapeworm can look like grains o rice or small segments of fettucine pasta. Eggs are released from the segments of tapeworm, which are in turn ingested by flea larvae. Flea larvae can live in a range of environments, ranging from in your home’s carpet or between floorboards, to your dog’s kennel and bedding and even in the soil of your garden.

The flea larva is the intermediate host for the tapeworm. As the flea larvae develops into an adult flea, the tapeworm lives inside it. When the flea becomes an adult, it will jump onto a dog to feed. As the dog scratches and grooms itself with its teeth, it can inadvertently ingest adult fleas. If the adult flea is infected with tapeworm larvae, then the dog will now become a final host to the tapeworm. The entire lifecycle of Dipylidium caninum only takes 3 weeks to complete.

Clinical Features

Although they are unpleasant to look at, Tapeworms are rarely serious in dogs. The most common sign that your dog may be infected with a Tapeworm is irritation or itchiness around the anal region (infected dogs may show classic “scooting” behaviour) and you may even notice segments of Tapeworm that have been shed “crawling” around the anal area or in your dog’s faeces. Dogs with very heavy infestations can get intestinal obstruction leading to further complications, such as diarrhoea, vomiting and weightloss, but this is rare.

Diagnosis
Diagnosis of many canine intestinal worms is done by a method known as a faecal flotation. In this method, a portion of the dog’s faeces is mixed up with some saline solution and then a drop of this solution is placed on a slide and examined under a microscope for the presence of different worm eggs.

Because Tapeworm eggs tend to be contained within segments of the tapeworm, a faecal floatation examination generally will not show any tapeworm eggs, even if the dog is infected with the parasite. The most definitive way of diagnosing infection is from the vet or owner visualizing Tapeworm segments (“rice grains”) in the dog’s faeces or around the anal region.

Treatment
Praziquantel (Droncit) and Epsiprantel (Cestex) have been shown to be effective in the treatment of all species of canine Tapeworms. It is important to remember that simply treating an infected dog is not enough to prevent infection. It is also vital to eradicate the intermediate host or re-infection will occur.

Prognosis

With the correct diagnosis and treatment, the prognosis for recovery in dogs with tapeworm infection is excellent.

Zoonotic Potential (Possibility of Transmission to Humans)

Echinococcus spp. are a threat to human health. Although humans are accidental hosts (ie they are not part of the normal lifecycle), infection can occur and can be deadly. Echinococcus forms hydatid cysts, usually in the lungs, liver or brain or the intermediate host. In the normal lifecycle, the intermediate hosts are sheep, pigs, oxen or deer, however humans can sometimes act as an intermediate host. For this reason, dogs living in the country, especially in sheep farming areas, should be regularly wormed (every 4-6 weeks). This is particularly important for dogs that have access sheep offal or in dogs that hunt.

tapewormlifecycle

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