What is Hydatid Disease?
Hydatid disease, also known as hydatidosis
, is a parasitic infection of various animals, which can infect humans. The disease is caused by a small tapeworm living in dogs, dingoes and foxes.
Tapeworm eggs pass out in the faeces of infected dogs. If eaten by a suitable host, such as sheep, goats, pigs and cattle, these eggs may develop into hydatid cysts in the internal organs of the host, especially the liver, heart and lung. On the Australian mainland, these cysts also occur in several wild species 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 material containing hydatid cysts (eg. sheep liver) and becomes infected with hydatid tapeworms. See life cycle of hydatid tapeworm below.
Humans can also become infected by accidentally swallowing hydatid eggs. These eggs are minute and sticky and easily transferred from the dog to human hands. In humans, cysts may grow quite large, causing medical problems and necessitating surgical treatment. The disease is occasionally fatal.
Hydatid Disease in Tasmania
In the early 1960s, a control program was commenced by the state government, aimed at stopping transmission of hydatid disease to humans. At the time, the disease was extremely common in sheep and rural dogs in Tasmania, and a disturbing number of human cases, some fatal, were occurring.
The Tasmanian program was based on stopping the hydatid life cycle by denying dogs access to internal organs (offal) of sheep, cattle, goats and pigs.
Hydatid disease in Tasmania affects mainly dogs, sheep and cattle. Unlike mainland Australia states, 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 control 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 because the disease also affects native and feral animals.
To help prevent spread of hydatids there are restrictions on feeding offal to dogs. The requirements in relation to offal are:
- Raw offal (unless it has been treated as detailed below) must not be fed to dogs.
- 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)
- It has been cooked to a core temperature of 100 degrees Celsius for one minute or an equivalent treatment.
- It has been frozen solid (core temperature of minus 20 degrees Celsius) for 48 hours
Note: Requirements for offal to be commercially sterile and to be cooked, as described, are detailed in the Animal Health Regulations 2006, and the freezing of offal, as described, is contained in a recent order published on 29 June 2016.
Fresh offal (i.e. offal which is neither frozen nor cooked) will remain prohibited for either sale as dog food, or for feeding to dogs in Tasmania. Fresh offal has always been available for sale as pet food for non-canines (e.g. cats) and for human consumption. This will continue to be the case.
Offal is sometimes found in manufactured pet food. This is safe and legal to feed to dogs if it has been treated as described above. Note feeding ‘fresh’ pet mince that contains offal that has not
undergone an approved process to render it hydatid- safe is illegal.
Tasmania's Provisional Freedom
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 signals that we have reached a significant stage in the eradication process. The disease is now very rare in Tasmania. In order to maintain provisional freedom, and progress towards eradication, we must continue to do three things:
1. Detect and remove any residual infection
2. Minimise the risk of infection entering from the mainland
3. Permanently identify all imported livestock to enable differentiation at slaughter
Dealing with Residual Infection
Each year in Tasmania, up to 400,000 sheep and 60,000 cattle are inspected in abattoirs at slaughter. DPIPWE also receives information on hydatid disease incidence in sheep and cattle slaughtered in some mainland abattoirs. The infected flock or herd may be quarantined and progressively slaughtered. If any hydatid cysts are found, the property of origin is thoroughly investigated.
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 praziquantel
or evidence of treatment, such as the pill packet. This 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.
Hunting dogs and roaming pet dogs
Hunting dogs and roaming pet dogs
Hunting dogs and pet dogs that roam can be a significant risk for hydatids. This is because there is a risk that, when hunting/roaming, they may come across a carcase of a dead animal and eat the offal.
Hunters should always do the right thing by the farmer who allows them onto the property by treating their dogs for hydatids, with a wormer that contains praziquantel, before they go onto the property. A further step that hunters can take to help further reduce the risk is to muzzle the dogs while they are hunting, as this would prevent scavenging.
Livestock farmers who allow hunters onto their property should always insist that the hunting dogs are treated for hydatids beforehand and it would be quite reasonable to insist that hunting dogs are muzzled as well.
Pet dogs that are allowed to roam are a major problem for livestock farmers for two reasons – the risk of hydatids and other diseases spread by scavenging dogs and the risk of attacks on livestock. 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:
1. Do not feed dogs untreated raw offal (eg liver, heart, kidneys etc,) even if purchased from a butcher for human
consumption. Commercially prepared dog food that has been appropriately cooked or frozen is fine.2. Prevent access of dogs to dead
stock or offal from a home kill.3. Prevent dogs from roaming or straying.
4. Always wash hands thoroughly
after handling dogs. This is particularly important for children.5. Treat dogs at the right dose for their weight regularly with an all-wormer
treatment containing praziquantel.