Hydatid Disease

​​​​​​​​​​​​​​​​​​​​​​​​​What is hydatid disease?

Echinococcus-granulosis parasite

Echinococcus granulosus parasite seen under the microscope, © Peter M Schantz

Hydatid disease, also known as hydatidosis or echinococcosis, is a type of  tapeworm infection that can occur in various species of animals, including humans.

Echinococcus granulosus is the tapeworm which causes hydatid disease in Australia.

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 sheep, cattle, 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.

Legislation

To help prevent the potential spread of hydatids in Tasmania 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 Jun​​e 2016 order published in the Tasmanian Gazette details the acceptable requirements for freezing. These conditions include the following:
  • Raw, untreated offal (from any livestock – imported or of Tasmanian origin) 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 thermally treated using acceptable thermal parameters, in a verifiable manner (i.e. time, temperature, batch records maintained), OR
    • It has been frozen solid to a core temperature of minus 20 degrees Celsius for a minimum of 48 hours, with records available to allow verification of this process, OR
    • The process or treatment applied has been approved by the Chief Veterinary Officer of Tasmania.
NOTE: Offal may be present in commercially manufactured pet food that has undergone an approved treatment process. This is safe and legal to feed to dogs. Please note that raw, 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:
  1. Detect and remove any hydatid infection in dogs.
  2. Minimise the risk of hydatids in dogs entering Tasmania.
  3. Control or remove any stray dogs.
  4. Permanently identify all imported livestock to enable tracing. 
  5. 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​.
  6. Ensure carcase disposal of stock animals is undertaken in a manner that prevents access by dogs and other animals.
  7. 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

Screening for Echinococcosis using ultrasonography, © WHO

cause serious disease and can be fatal. If you have any concerns, please speak with your doctor.

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. DPIPWE 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:
  1. A veterinary certificate (from a registered veterinarian) detailing effective treatment within 14 days of export to Tasmania, OR
  2. A Statutory Declaration (made by the dog owner) indicating effective treatment within 14 days of export to Tasmania, OR
  3. Evidence of effective treatment, such as the worming product packet.
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.

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. Dogs that are used for hunting should be regularly wormed for hydatids, especially prior to being used on someone else’s property. Muzzling dogs during their hunting activities is recommended to help reduce the likelihood of scavenging.

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:
  1. Never feed untreated, raw offal to dogs.
  2. Prevent dogs gaining access to dead stock animals, dead/burial pits or raw, untreated offal.
  3. Prevent dogs from roaming, scavenging, or straying. Livestock farmers have the legal right to kill any dog that strays onto their property under the Dog Control Act 2000. Dog owners, especially those in rural or semi-rural areas, should never allow their dog to roam.
  4. Always wash hands thoroughly after handling dogs.
  5. Treat dogs at the correct dose and regularly with a worming treatment containing the active ingredient praziquantel. For any questions regarding worming, please speak with your veterinarian.

Livestock Data Link (LDL)

Livestock Da​ta Link is an initiative by Meat & Livestock Australia which allows participating abattoirs and producers to access carcass information that conveys the cost of non-compliance in market specifications including animal health and welfare issues detected at the abattoir (such as hydatid disease).

Producers (that use participating abattoirs) can access carcass data for their animals through the Livestock Data Link Portal. The animal health information present within this data can serve as an extremely valuable resource for a livestock producer (and their veterinarian) by helping to inform decisions relating to disease control, disease management and livestock performance.​

Remember, hydatids is a notifiable disease, meaning that confirmed cases or suspicion of the disease must be reported immediately.

Further information

If you suspect hydatid cysts in a carcase or offal, please contact AnimalDisease.Enquiries@dpipwe.tas.gov.au,
call 1800 675 888, or contact your registered veterinarian - (testing is free).

Information regarding sample collection and submission can be found on the Biosecurity Tasmania Animal Health Laboratory website.

Hydatid disease poster and factsheet

  Hydatid Poster

 

  Hydatids Factsheet

 

Glossary of hydatid images

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.

Multiple solid, firm hydatid cysts (circled) in the liver of a cow​​. © Animal Health Laboratory, Tasmania.

A single hydatid cyst in the liver of a steer. © Animal Health Laboratory, Tasmania.

A clear, fluid filled hydatid cyst (circled) in part of a bovine lung. © Animal He​​alth Laboratory, Tasmania.

Numerous small, firm hydatid cysts containing cream to yellow coloured fluid in the liver of a steer. © Animal Health Laboratory, Tasmania.

Two hydatid cysts (circled) in the liver of a bull. © Animal Health Laboratory, Tasmania.

Multiple fluid filled hydatid cysts in the lungs of a cow. © Animal Health Laboratory, Tasmania.​


Contact

Animal Disease Enquiries
13 St Johns Avenue
New Town TAS 7008
Phone: 03 6165 3777
Email: AnimalDisease.Enquiries@dpipwe.tas.gov.au

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