Tapeworms are different in structure and behaviour to other intestinal worms of dogs and cats. The key difference is that every dog and cat tapeworm species requires an intermediate host to complete its life cycle.
Depending on the tapeworm species, these intermediate hosts can include fleas, frogs, kangaroos and domestic animals such as sheep and pigs.
It’s the involvement of livestock in the life cycle of some tapeworms that has the greatest impact – not on the dog, but on the end product at the abattoir. And for humans, the hydatid tapeworm can be fatal (click here for more information on human hydatidosis).
Structurally, tapeworms are flat with a head and neck, followed by numerous segments, each with its own reproductive organs. The head usually has suckers to allow the worm to attach to the intestinal wall. In the neck region, new segments are continually being formed, while the mature segments at the end – which can contain large numbers of eggs – are cast off and pass out in droppings. Often these individual segments are seen around the anus of the dog or cat, looking like rice grains attached to the fur.
The most common tapeworms infecting dogs and cats in Australia are:
- Flea tapeworm (Dipylidium caninum )
- Taenia ovis, the cause of sheep measles
- Hydatid tapeworm (Echinococcus granulosus)
The flea tapeworm is the most common. While the adult tapeworm (which can be over 40cm in length) lives in the small intestine of the dog, fox or cat, it requires fleas and lice to complete its life cycle. Once a mature tape segment passes out in faeces, it breaks open, releasing its eggs. These are ingested by a flea larva. The egg develops into an immature form of the tapeworm inside the flea, and when the flea is eaten by a dog or cat, the immature form develops into the adult tapeworm in the pet’s gut, completing the life cycle.
Preventing flea infestations during the warmer months is the easiest way to stop your pet becoming infected by Dipylidium caninum. If diagnosed (often by owners seeing the small white segments around their pet’s anus, or itchiness may cause the pet to ‘scoot’ along the floor), worming with any product containing praziquantal will kill the tapeworms. Heavy infestations, especially in puppies and kittens, can cause poor growth, abdominal discomfort and diarrhea.
Taenia ovis (otherwise known as Cysticercus ovis) is the dog tapeworm that causes sheep measles – one of the most common causes of carcass condemnation and subsequent loss of farm income. It is common in the Crookwell district.
Sheep and goats are the intermediate hosts and carry the immature cystic stage of this tapeworm in muscle tissues (the “measles”), while dogs and foxes are the final hosts and carry the adult tapeworms in their intestines.
The Taenia ovis life cycle starts when eggs are passed out in a dog’s droppings. Sheep or goats then eat the eggs when grazing pasture. The swallowed eggs hatch into larvae and these develop into cysts in muscle tissue. Dogs get re-infected by eating these infective tapeworm cysts in uncooked sheep or goat meat.
The hydatid tapeworm lives as an adult in the intestine of canines (without causing illness), but it needs to pass through an intermediate host to mature. These are many and varied and include humans (often with fatal consequences) and domestic livestock and wildlife, including sheep, goats, cattle, pigs, horses, kangaroos and wallabies.
When hydatid eggs pass out in dog faeces, it is easy for people patting their pet, for example, to pick up eggs on their hands. If good hygiene is not observed (washing hands before eating), the eggs are ingested, hatch into larvae that penetrate the intestinal wall and migrate to a range of organs, including liver, lungs, heart and brain. Here they form large cysts containing thousands of immature tapeworms. In humans, this leads to serious illness, surgery and sometimes, death. When the intermediate host is the sheep or other livestock, the dog becomes re-infected when fed offal containing the cysts.
Regular worming with praziquantal and avoiding feeding dogs offal are the two keys to keeping dogs free of the hydatid tapeworm and preventing human infection.
The flea tapeworm is often diagnosed when owners see tape segments crawling around their dog’s anus. At CVH, we can identify tapeworm eggs by microscopic faecal examination.
Prevention and treatment
For the flea and sheep measles tapeworms, three monthly worming with praziquantal will keep dogs free of tapeworms. When dogs have access to offal, it is essential to worm dogs every 6 weeks to prevent infection with the hydatid tapeworm.
Prevention is safest. For the hydatid and sheep measle tapeworms, avoid feeding dogs offal and uncooked sheep and goat meat, and keep dogs under control to prevent access to offal. For the flea tapeworm, talk to us about implementing a regular flea control program, both for your pet and the pet’s environment.