This report was written by Dr Nick Sangster, a Senior Lecturer in Veterinary Parasitology, from the Department of Veterinary Anatomy and Pathology at the University of Sydney. It was commissioned by Pfizer Animal Health (Back to general Health)

Breeders of Quality Cairn Terriers • Cairn Care - Intestinal Worms • WORMS, DOGS AND PEOPLE Several species of worm infest the intestines of dogs. They are named by their shapes: roundworms, hookworms, whipworms and tapeworms. A survey in Australia suggests that as many as 1.3 million of our domestic dogs are infected with worms. Whilst in the intestines of dogs, their host, worms produce microscopic eggs which pass into the droppings. Veterinarians can often diagnose parasite infection by identifying eggs in the droppings. In general, it takes several days for the eggs to become infective for other dogs. Infection occurs after eating infective stages, although hookworms can penetrate the skin. Once in the dog the parasite migrates to the intestine and the cycle starts over. Most worm species have similar life cycles but the tapeworms are very different as they must pass through an alternative host before returning to the dog. Dogs are usually infected with several parasite species simultaneously. "Wormy" dogs have a rough, dull coat, are underweight, have a pot belly and many have diarrhoea. Sometimes these parasites get into a human instead of a dog. Although this is rare the consequences can be fatal.

Roundworm

ROUNDWORMS (e.g. Toxocara canis, Toxascaris leonina) Roundworms include at least two species and are up to 15 cm long. They are most common in puppies and are sometimes seen in their vomit. Apart from the simple worm-egg-worm life, roundworms have other tricks which ensure the species survive. In bitches the worms lie dormant in the tissues, sometimes for years and when the bitch becomes pregnant the worms penetrate the placenta and infect the foetus. Even an unborn dog can have worms. Heavily infected puppies may suffer pneumonia and later suffer a blocked bowel. Puppies look "wormy" and severe cases are fatal. When the eggs of dog roundworms are eaten by humans, particularly children, they can travel to the liver and lungs. The most serious consequences arise when worms enter the brain or the eye but fortunately this is a rare occurrence. Control of roundworms is difficult. Millions of eggs are produced and each can survive many years in the dog's environment. Further, infection of unborn puppies means that infection is difficult to avoid even when the kennel and yard are kept clean. Fortunately, drug treatment is effective if performed regularly in the first three months of the puppy's life.

Hookworm

HOOKWORMS (e.g. Ancylostoma spp., Uncinaria stenocephala) The species of hookworm causing severe disease is common in Queensland but species found further south and in New Zealand are less serious. Adult worms, up to 15 mm long, live in the intestine where they lacerate the walls and suck blood. Eggs are produced by the million. They contaminate the ground and develop to small larvae. In the warm, moist tropics development occurs rapidly. Larvae can enter their next host via the mouth, the skin or via the milk to the suckling puppy. Dermatitis, often between the toes, may follow skin penetration. However, the most severe effect is a blood loss anaemia which can be fatal in 2-3 week old puppies. Affected animals are pale and weak, sometimes with bloody diarrhoea. Humans have been infected after walking barefooted near where dog droppings have been left. Larvae enter and migrate under the skin causing a disease called "creeping eruption" and can reach the intestine. Control relies on removing droppings twice a week and treatment three monthly in adult dogs, especially bitches. Puppies require regular weekly to fortnightly treatments as well as iron tonics.

Tapeworm

TAPEWORMS (e.g. Dipylidium caninurn, Echinococcus granulosus, Taenia spp.) Several types of tapeworms infect dogs. One, Dipylidium, or the flea tapeworm, lives in the dog but the eggs must be eaten by an insect. A cyst forms in the insect and, when eaten by the dog, develops into another tapeworm. Segments of this parasite look like cucumber seeds when passed in droppings. The segments irritate the skin around the anus causing dogs to "scoot" along the carpet to relieve their itchy behinds. Children can also become infected by eating fleas and may suffer itchy behinds, too, but it is not serious. A second class of tapeworms, the taeniids, range in size from 5 mm to 5 m and generally cause few problems to the dog. The intermediate, cyst stage of these tapeworms occur in grazing animals and dogs become infected with worms when fed fresh meat or offal. However, a form of the hydatid tapeworm Echinococcus is serious and potentially fatal in humans. The dog is the main host of the tiny hydatid tapeworm. Worm eggs are eaten by sheep and develop into large cysts. Humans can become accidental hosts by eating eggs. Like in sheep, the cysts in humans, grow, squeezing vital organs like the liver and lungs. About 100 human cases go to surgery annually in Australia, most of these come from the cooler areas of the mainland. The disease is very rare in Tasmania and New Zealand and declining in the rest of Australia. Although it is mostly a disease of rural dogs, owners from the city may be exposed to infection from hunting dogs allowed to eat the flesh of any native or grazing animal. Control of hydatids has been instituted by governments in many regions. It is based on not allowing dogs to eat uncooked meat or offal and monthly treatment of dogs which are exposed to infection with an effective antiparasite drug.

Whipworm

WHIPWORMS (Trichuris vulpis) Whipworms have simple cycles and the species in dogs does not infect humans. Although around 20% of dogs are infected they only cause disease in severe cases. Worms suck blood and cause a bloody, smelly diarrhoea. The eggs are very tough and survive many years. Control aims at preventing a build-up of eggs by treating dogs at intervals of about three months which does not allow the worm to grow to adulthood.

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