What is hydatid disease?
Hydatid disease, also known as hydatidosis or echinococcosis, is a type of tapeworm infection that can occur in various species of animals, including humans. The full name of the parasite that causes this disease in Australia is
Echinococcus granulosus parasite seen under the microscope
Photo: Peter M Schantz
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 are eaten by a suitable host, such as grazing sheep, cattle, goats or pigs, these eggs may develop into hydatid cysts in the internal organs (‘offal’) of the host, especially the liver, heart and lungs. 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 is completed when a dog, dingo or fox eats infected offal and consequently becomes infected. See a visual representation of the hydatid life cycle below.
What are the signs an animal may be infected with hydatids?
Dogs, dingos, foxes, sheep, goats, cattle and pigs typically do not show signs of infection.
Infected wallabies may show signs related to lung cysts including breathing issues, poor body condition or slow movement and similar behaviours which lead to an increased susceptibility to hunting/predation.
Hydatid disease in Tasmania
In the early 1960s, a control program was commenced by the Tasmanian government, aimed at eliminating transmission of hydatid disease from animals to humans in an effort to improve public health. 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 identifying (and treating) infected dogs and denying dogs access to the internal organs (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 native or feral animals. Tasmania's fox detection and eradication efforts should ensure that foxes have minimal impact.
The program was extremely successful in that 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 and foxes which are involved in the hydatid lifecycle.
To help prevent the spread of hydatids there are restrictions on feeding offal to dogs. The full requirements for commercial sterilisation and cooking are detailed in the
Animal Health Regulations 2016. The
June 2016 order published in the Tasmanian Gazette details the acceptable requirements for freezing. These conditions include the following:
Raw, untreated offal must not be fed to dogs.
Treated offal, or pet food containing offal may be fed to dogs, or sold as dog food provided that:
It is commercially sterile. This means that it has been treated in a way that it can be stored for extended periods without refrigeration (e.g. canned or various hard dried products) OR
It has been frozen solid to a core temperature of minus 20 degrees Celsiusfor a minimum of 48 hours, with records available to allow verification of this process.
Raw, untreated offal will remain prohibited for sale as dog food or for feeding to dogs in Tasmania. This includes feeding fresh mince to dogs that contains offal that has not undergone an approved process. Offal may be present in commercially manufactured pet food. This is safe and legal to feed to dogs as the commercial process is subject to the legislation stipulated above. Please note that raw 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, and progress towards eradication, we must continue to reduce the risk of hydatids through the following steps:
Detect and remove any hydatid infection.
Minimise the risk of hydatid infection entering Tasmania.
Permanently identify all imported livestock to enable differentiation at slaughter.
Assess carcasses (e.g. during the slaughter processes at abattoirs, knackeries, and home kill operations) for hydatid cysts. Any suspect lesions should be submitted to the
Animal Health Laboratory for analysis.
Ensure disposal of carcasses is done in a manner that prevents access by dogs and other animals.
Worm dogs regularly.
Prevent dogs from scavenging, straying, and roaming.
Always wash hands thoroughly and practice good hygiene after handling dogs. This is particularly important for children.
Can people contract hydatids from infected animals?
Yes; humans can become infected by accidentally swallowing hydatid eggs. Hydatid infections in people have the potential to cause very serious disease and can be fatal. If you have any concerns, please talk to your doctor. Hydatid eggs are very small, sticky and are thus easily transferred from an infected dog to human hands such as via the dog’s coat or contaminated footwear.
In areas with a high level of contamination (unlikely in Tasmania), eggs may also be transmitted through such routes as the inhalation of dust containing eggs or contact with flies contaminated with eggs.
Wind can also facilitate movement of hydatid eggs in the environment.
Screening for Echinococcosis using ultrasonography (Photo courtesy of the WHO)
What happens if my stock animals are found to have hydatids?
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 and disease findings in carcasses (e.g. lesions suspicious of hydatids) reported to DPIPWE. DPIPWE also receives information on sheep and cattle 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 through your veterinarian.
Hydatid cyst in cattle lung. Photo: courtesy of Dr Andrew Davis (Animal Health Laboratory, Biosecurity Tasmania)
Multiple hydatid cysts in cattle liver. Photo courtesy: Graeme Knowles (Animal Health Laboratory, Biosecurity Tasmania)
Minimising the risk of entry Dogs entering Tasmania are required to be treated for hydatid tapeworms.
Dogs are allowed entry to Tasmania if accompanied by a veterinary certificate or a Statutory Declaration of treatment within the previous 14 days with the drug
or evidence of treatment, such as the pill packet. Praziquantel is a common, harmless and highly effective treatment against tapeworms, if given at the right dose rate and it is found in many types of 'all wormer' tablets for dogs.
The major air and sea transport operators are advising people booking travel for dogs to Tasmania of the special entry requirements for dogs, and are advising them to call the free-call telephone number:
1800 684 215
This telephone number provides a 24 hour recorded information service with details of the entry requirement for dogs.
Recommendations for hunters and farmers
Farmers should dispose of dead stock animals as soon as possible and in such a way that prevents access by dogs and other animals.
Hunting dogs and pet dogs that roam or scavenge can be at significant risk of hydatid infection. This is because there is a possibility they may come across the carcass of a dead, infected animal and consume the infected offal.
Hunters should always do the right thing by the farmer who allows them onto the property by treating their dogs for hydatids, before they go onto the property. An additional step that hunters can take to help further reduce the risk is to muzzle the dogs while they are hunting, as this can help prevent scavenging.
Livestock farmers who allow hunters onto their property should always insist that the hunting dogs entering their premise have been treated for hydatids prior to entry. It would be quite reasonable to also insist the dogs be effectively muzzled while on the farmer’s premise.
Dogs that can roam are a major problem for livestock farmers. Not only can roaming dogs create a biosecurity risk or increase the risk of hydatids, these dogs can also engage in attacks on livestock, which can have negative economic and welfare consequences for the farmer. Livestock farmers have the right to kill any dog that strays onto their property. So, pet dog owners, especially those in rural or semi-rural areas, should never allow their dog to roam.
Recommendations for all dog owners
Although Tasmania is considered to be provisionally free of hydatid disease, there are a number of simple recommendations that all dog owners should continue to observe:
Do not feed dogs untreated, raw offal (e.g. liver, heart, kidneys etc,) even if purchased from a butcher for human consumption.
Prevent dogs gaining access to dead stock animals, dead/burial pits or offal from a home kill.
Prevent dogs from roaming, scavenging, or straying.
Always wash hands thoroughly after handling dogs. This is particularly important for children.
Treat dogs at the correct dose and regularly with an all-wormer treatment containing the active ingredient- praziquantel. For any questions regarding worming, please speak with your veterinarian.
Hydatid Disease Poster