Hydatid disease

Hydatid disease is a zoonotic disease caused by the intermediate stage of the dog tapeworm Echinococcus granulosus. It causes cyst formation in internal tissues such as the liver, lungs and brain of grazing animals and people.

The hydatid tapeworm life cycle involves a definitive host (dog or dingo), which hosts the adult tapeworm in the gut, and intermediate hosts (sheep, goats, cattle, pigs, kangaroos and wallabies), which are host to the watery cystic stage, most commonly in the liver and lungs.

Accidental ingestion of tapeworm eggs by people can result in multiple cysts occurring in internal tissues. Hydatid disease is a serious infection in people and may be fatal in a small number of cases. In Queensland, there is an average of 10 cases of hydatid disease reported each year.

Hydatid disease occurs worldwide. In Queensland it is most prevalent in rural areas where there is a close association between dogs and dingoes with cattle, sheep, goats, pigs, kangaroos and wallabies. The disease can occur in any area where dogs consume raw offal.

Dogs, dingoes, sheep, goats, cattle, pigs, kangaroos, wallabies

Dogs

Dogs are host to adult tapeworms; however, they do not display any signs of infestation. The adult worm measures 6–15mm and diagnosis of infestation relies on microscopic examination of the faeces to identify tapeworm eggs. Dogs become infected by eating cysts (intermediate tapeworm stage) in uncooked offal from infected sheep, cattle, pigs and wildlife.

Cattle, sheep, pigs and wildlife

There are usually no obvious signs of disease in these animals, even when cysts are detected at slaughter.

People

Symptoms in people vary according to the number, size and location of cysts within the body. Hydatid disease can cause serious illness and death.

Hydatid eggs are dispersed in the environment via the faeces of infected dogs. Dogs can host several thousand adult tapeworms in their intestine. The sticky eggs in their faeces can also adhere to the dogs' coats.

Hydatid disease (cyst formation) occurs as a result of ingesting the microscopic eggs. Grazing animals are infected by eating contaminated pasture.

People are infected when they accidentally ingest the eggs excreted in dog faeces. This can occur by patting a dog then touching your mouth, by kissing a dog, through items contaminated with soil or by consuming contaminated food or water. People are at increased risk of infection if they live in grazing areas where dogs are used to herd cattle and sheep.

Dogs and dingoes consuming the cysts within offal of livestock or wildlife completes the life cycle by creating a new generation of adult worms.

Person-to-person and livestock-to-person transmission do not occur.

Dogs

Control involves breaking the tapeworm life cycle.

To break the tapeworm life cyle:

• regularly worm all dogs with praziquantel
• do not feed dog raw offal or carcasses
• do not allow dogs to scavenge on carcasses.

It is especially important that dogs in rural areas or those that may have contact with wildlife or feral animals receive regular treatment with praziquantel. Praziquantel kills the adult hydatid tapeworm and should be administered at regular intervals.

Regular worming of dogs for tapeworm will also control the tapeworms responsible for sheep measles (Taenia ovis) and bladder worm or false hydatids (Taenia hydatigena). Monthly worming can conveniently control all three parasites.

Ask your local veterinarian about effective tapeworm control.

Treatment of grazing animals

There is no treatment for hydatid cysts in grazing animals. If cysts are present at slaughter, lungs, livers and hearts are condemned.

Treatment for humans

Treatment involves the surgical removal of cysts.

To prevent hydatid disease in people:

• regularly worm all dogs with praziquantel
• do not let your dog eat raw offal or carcasses
• wash hands after handling dogs
• wash hands before handling and eating food and before smoking
• do not allow dogs to lick your face
• do not allow dogs to defecate in or near vegetable gardens and children's play areas
• avoid contact with dog faeces.

For medical advice contact your doctor or health clinic or call 13HEALTH (13 43 25 84).