How is it spread?
It is spread via the faecal-oral route. Hydatid eggs pass out in the faeces of infected dogs, dingos and foxes, often contaminating pasture. If the eggs in the contaminated pasture are eaten by a suitable host, such as grazing cattle, sheep, goats or pigs, these eggs may develop into cysts in their internal organs (‘offal’), especially the liver, heart and lungs (see images below). On the Australian mainland, these cysts also occur in several wild animals including kangaroos and wallabies.
Hydatid cysts contain large numbers of what are basically new tapeworm heads. The life cycle of the tapeworm is completed when a dog, dingo or fox eats raw, untreated, infected offal and consequently becomes infected themselves.
In areas with a high level of environmental contamination (very unlikely in Tasmania), eggs from dog faeces may be transmitted through other routes such as the inhalation of dust containing eggs or potentially via flies. Wind and water can also facilitate movement of eggs in the environment.
What are the signs an animal may be infected with hydatids?
Animals typically do not show signs of infection. On the Australian mainland, infected wallabies may show signs such as breathing issues, poor body condition, slow movement and similar behaviours which ultimately make them more susceptible to predation.
Hydatid disease in Tasmania
In the early 1960s, a control program to improve public health was commenced by the Tasmanian Government, aimed at eliminating transmission of hydatid disease from animals to humans. At the time, the disease was extremely common in sheep and rural dogs, and a disturbing number of human cases were occurring.
The Tasmanian program was based on treating infected dogs and denying dogs access to the offal of sheep, cattle, goats and pigs.
Hydatid disease in Tasmania affects mainly dogs, sheep and cattle. Unlike mainland Australia, Tasmania does not have dingoes and there is no known involvement of other native or feral animals. Tasmania is also considered to be free from the presence of foxes.
The program was extremely successful; it appears that transmission of the disease to humans in Tasmania ceased in the early 1970s. In contrast, no hydatid disease control programs have been attempted on mainland Australia due to the sheer number and distribution of wild dogs, dingos, foxes and other susceptible wildlife.
Legislated treatment options for offal
Untreated offal (from any cattle, sheep, goats or pigs, imported or of Tasmanian origin) must not be fed to dogs.
To help prevent the potential spread of hydatids in Tasmania, penalties apply if these restrictions are not adhered to.
Freezing is the preferred method where offal is being treated in the home environment:
(The June 2016 Order published in the Tasmanian Government Gazette details the acceptable parameters and record keeping requirements for freezing offal.)
There are several other acceptable treatment methods available under Tasmanian legislation:
commercial sterility - where the offal has been subjected to commercial processing (for example canned or various hard, dried products);
thermal treatment (cooking); or
another method approved by the Chief Veterinary Officer of Tasmania.
The Animal Health Regulations 2016 (Sections 15 and 17) detail the requirements for commercial sterilisation and cooking. Strict conditions apply to record keeping for these treatments.
NOTE: Untreated offal is permitted for sale as food for non-canines (e.g. cats) and for human consumption.
Tasmania's provisional freedom from hydatid disease
In February 1996, Tasmania was declared provisionally free of hydatid disease in dogs and sheep, following disposal of the last known infected sheep flocks. This does not mean that hydatid disease has been eradicated from Tasmania, but indicates that we have reached a significant stage in the eradication process. The disease is now rare in Tasmania. To maintain provisional freedom, we must continue to reduce the risk of hydatids through the following steps:
Detect and remove any hydatid infection in dogs.
Minimise the risk of hydatids in dogs entering Tasmania.
Control or remove any stray dogs.
Permanently identify all imported livestock to enable tracing.
Assess carcases (e.g. during the slaughter process at abattoirs, knackeries, and home kill operations). Any lesions suspicious for hydatids must be submitted to the
Animal Health Laboratory for analysis. If you see any lesions suspicious for hydatids in farm animal offal, please contact Biosecurity Tasmania and a veterinary officer will co-ordinate the submission to the
Animal Health Laboratory.
Ensure carcase disposal of stock animals is undertaken in a manner that prevents access by dogs and other animals.
Manage dogs appropriately (see below 'Recommendations for all dog owners').
Can people contract hydatids from infected animals?
Yes; humans can become infected by accidentally swallowing hydatid eggs.
In being very small and sticky, hydatids eggs are easily transferred from an infected dog to human hands such as via the dog’s coat or contaminated items such as footwear. Hydatid infections in people have the potential to cause serious disease and can be fatal. If you have any concerns, please speak with your doctor.
Screening for Echinococcosis using ultrasonography, © WHO
What happens if my stock animals are found to have hydatids?
Positive cases of hydatids in animals are investigated by Biosecurity Tasmania. Depending on the situation and the details surrounding a hydatid detection, the infected flock or herd may be quarantined and progressively slaughtered. Each year in Tasmania, up to 400,000 sheep and 60,000 cattle are inspected in abattoirs. Any lesions suspicious for hydatid cysts found at Tasmanian abattoirs, are sent to the Animal Health Laboratory for testing. This is part of Biosecurity Tasmania’s hydatid surveillance program. NRE Tas also receives information on sheep and cattle of Tasmanian origin slaughtered in some mainland abattoirs.
Hydatid disease in animals is a
notifiable disease, meaning that confirmed cases or suspicion of the disease must be reported immediately. This can be done by calling the
Emergency Animal Disease Watch Hotline (1800 675 888) or via your registered veterinarian.
Minimising the risk of entry
Dogs entering Tasmania are required to be treated for hydatids.
Dogs are allowed entry to Tasmania if accompanied by:
The major air and sea transport operators are advising people booking travel for dogs to Tasmania of these special entry requirements, and asking them to call the free-call telephone number (1800 684 215), which provides a 24 hour recorded information service with details of this entry requirement.
Hydatid cysts can occur in a range of offal and occur most commonly in the liver, lung and heart. Generally the raised cysts extend from the surface of the organ into the body of the organ. These cysts often have a pale white to slightly translucent wall and contain clear fluid (with microscopic hydatid sand/parasitic scolices). The cysts can vary from 1-2 cm to 7-8cm in diameter. Degenerate hydatid cysts will have collapsed pale white, firm walls often with gritty (mineral) deposits and can vary from 5mm to 3-4cm in diameter.