Zoonotic diseases
Hydatid disease 

What is hydatid disease?

This disease is associated with cysts (hydatid cysts) that can form and grow in the liver, lungs, brain, kidneys, bones and other tissues. This occurs in humans but also in animals such as cattle, pigs, goats, wallabies and kangaroos.

These cysts are stages in the life-cycle of a small tape-worm of dogs and dingoes. The dog or dingo eats the cysts, the tapeworm develops from them, and the eggs that are shed develop into new cysts if humans or animals, other than dogs or dingoes, eat these microscopic eggs. 

Is it common in Queensland?

Human hydatid disease is most common where there is regular contact between dogs and sheep and where dogs are fed raw offal (lung, liver, kidney etc) from sheep especially, but also cattle, wallabies, kangaroos or feral pigs. If dogs are fed offal containing hydatid cysts, a high proportion become infested with the tape-worm.

The true level of hydatid disease in humans in Queensland is hard to determine because many cases go undetected or unreported. About 10 human cases are notified each year. These are generally in older people who were exposed as children, many years ago. Newly detected childhood cases are a major concern because they indicate active infection is occurring.

Hydatid cysts are commonly found in sheep and cattle at slaughter in Queensland. While many of these cysts are coming from exposure of sheep and cattle to dingo faeces containing hydatid eggs, producers should also review the management of their domestic or working dogs to ensure they are not a source of infection for their livestock or for people.

How could I get the disease?

People become infected when the tapeworm's eggs are transferred to the mouth on fingers eg while smoking, or on food. If a dog has the tape-worm, eggs pass out of the animal with faeces and the environment becomes contaminated. The dog may roll in this area and the eggs may transfer to the coat. Usually, the eggs get onto a person's hands as they pat a dog. Occasionally people may be exposed to eggs present in grass contaminated with dog or dingo faeces.

Are any groups at particular risk?

Due to their close contact with dogs and their tendency to transfer eggs to their mouths with their hands, children are most at risk.

The risk of hydatid disease is highest in rural areas or on the edge of cities where dogs and other grazing animals or wildlife come into contact. People in large cities whose dogs are only fed proper pet meat or canned/dry dog food are at much lower risk but should still take precautions against hydatid disease.

Where does the disease occur?

Usually sheep and dogs or dingoes and wallabies/kangaroos are needed to allow the tape-worm's life cycle to be completed. So any area where these combinations occur can be at risk from this disease.

While the risk of hydatids has been well recognised in sheep producing areas, the popularity of working dogs in cattle producing areas of Queensland has increased dramatically in recent years. This has led to a potential increase in the risk of hydatid disease in people because of the large numbers of dogs now being kept on farms that have not traditionally kept working dogs. Recreational pig hunting is also a popular sport, and people in rural or urban areas who keep pig dogs have also been identified as a group at particular risk of contracting hydatid disease from their dogs. Pig dogs often work unsupervised in rural areas where animal carcasses are found and can become infected quite easily.

What treatments are available?

With human hydatid disease, the cysts usually need to be removed by surgery. Some drugs can be used in special circumstances, but their effectiveness is sometimes disputed.

Hydatid tapeworm infection in dogs can be treated with a drug called Praziquantel. This drug is highly effective at controlling all stages of hydatid tapeworm infection in dogs, preventing them from shedding eggs in their faeces. To ensure dogs never pass hydatid tapeworm eggs in their faeces they should be dosed with worm tablets containing praziquantel every 6 weeks.  Praziquantel is now a common ingredient in most "all wormer" worming preparations available from veterinarians, produce stores and from supermarkets and pet shops, but people should read the label of any worm tablets carefully to ensure this drug is present. Worm tablets containing only praziquantel can be purchased where necessary and this may represent a cost saving, especially in working dogs.

What are the keys to prevention?

• Ensure children and adults wash their hands after handling dogs of any description and before eating or smoking. 
• Don't allow dogs access to uncooked sheep, wallaby, kangaroo, cattle or feral pig offal (including lungs, liver, kidneys and intestines).
• Restrain working dogs to prevent them from roaming and getting access to dead animal carcasses, especially sheep, wallaby or kangaroo carcasses. Producers with large numbers of dogs should construct dog runs and cages for their dogs.
• Treat dogs regularly for tape-worms with tablets containing praziquantel.
• Avoid handling dingoes, whether alive or dead. Take care in areas that could be contaminated with dingo faeces.

This information was developed jointly by Queensland Health and the Department of Primary Industries and Fisheries.

See other Zoononoses (Diseases which can be transmitted from animals to humans) 

Last updated 23 January 2008