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This article was published in 1976
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Hydatid Control Programme
R.C. Denyer, B.V.Sc., Acting Principal Veterinary Officer, Division of Animal Industry Department of Agriculture, NSW.
Hydatid disease occurs at a very variable rate in different parts of the world. In those areas where the disease is uncommon, there are unlikely to be endeavours to further reduce its incidence.
The incidence of the disease in man is generally expressed as the number of new cases per 100,000 persons per annum. The figures quoted below. indicate the prevalence of the disease on this basis for the decade 1950 to 1959.
| Australia | 1.6 | (Tasmania 9.3) |
| Italy | 1.6 | (Sardinia 14.2) |
| Yugoslavia | 3.4 | (Dalmatia 27.4) |
| New Zealand | 4.7 | (localised areas 9.3 to 26.8) |
| Greece | 8.3 | |
| Cyprus | 12.9 | |
| Uruguay | 17.5 |
In Iceland a century ago 2% of the population had recognisable hydatid disease. This is equivalent to an annual rate of perhaps 50 to 60 per 100,000 per year or more. An autopisy survey at that time showed that some 22% were infected with hydatids to a varying degree.
From the figures quoted above, it is not surprising that Iceland was the first country to wage war on hydatids. It is also understandable that New Zealand should have been concerned with its incidence last century and that it took its first steps towards reducing that incidence in 1937. One can understand, too, why the Tasmanians introduced a full pilot eradication scheme in 1964.
Before considering the various eradication schemes that have been introduced, let us consider the factors that influence the prevalence of the disease.
a). Only dogs and dingoes in this country and various other canines in other areas carry the hydatid tapeworm.
b). In most circumstances, dogs become infected by eating sheep offal fed to them or secured from carcases. Dingoes become infected by eating marsupials and, in odd cases, sheep.
c). The human disease is very much more common in rural than in urban populations.
Societies which have few or no dogs or which have no sheep have least hydatids. However, in this country dogs may sometimes become infected by being fed from (sic) marsupials.
Before considering what ought to be done in an eradication campaign, let us look at what has been attempted in other areas.
Iceland.
Because the incidence of hydatids in man was known to be high, a Danish parasitologist and physician, Dr. Harald Krabbe, was sent to investigate and in 1864 he wrote a booklet for distribution to every household in Iceland by the Government.
That booklet explained in very considerable detail how hydatids was caused and how it could be prevented. It dealt, too, with the other conditions caused by tapeworms of the dog, namely Cysticercus tenuicollis or bladder worm cysts, common in this country, and gid, a disease fortunately not present in Australia, in which the brain of the sheep is attacked.
At that time one quarter of all adults in Iceland bore some signs of infection with hydatids and one person in very 50 or 60 was a known hydatid sufferer. Undoubtedly, every family had had its victims and the populous would be very receptive to the advice furnished.
Dr. Krabbe warned against keeping too many dogs, allowing them to live in the house and against fondling of dogs. This was particularly relevant when personal hygiene, particularly in the long winters with 18 hours of darkness, was so difficult. He warned against offal feeding and indicated that cooked meat only should be fed to dogs.
Having laid down the necessary preventive measures, the doctor then indicated the treatment to be administered to dogs.
These measures alone led to a dramatic reduction in hydatid disease. Later on other more sophisticated measures were introduced, but the net result has been that hydatid disease has been completely eliminated from Iceland. This has been one of the most spectacular success stories in disease eradication.
New Zealand
Again, because the incidence of hydatids in many was known to be substantial, official control measures were introduced in 1937. At that time the registration of dogs was required and arecoline tablets were to be given four times a year. The feeding of raw offal was condemned and leaflets were distributed, but the programme made very limited headway.
In 1947 there was a transition to the growth of local hydatid eradication committees, the programme at the time being based on education and treatment of dogs. Once again the progress was deemed to be inadequate and in 1959 the National Hydatid Council was formed. The Council prescribed techniques and methods to be used in eradication campaigns and prompted research extension and the provision of adequate diagnostic services.
Once the official campaign got underway with supervision by a team of inspectors, it was possible to show a marked downturn in the incidence of tapeworms in dogs and the presence of the disease in sheep. The programme has involved the annual testing of some 500,000 dogs per year for the presence of the hydatid tapeworm Echinococcus granulosus.
Tasmania
The Tasmanian campaign is similar to that in New Zealand. It was launched following earlier trials in 1964.
Basically the extension programme lays down the following essential ingredients of the control programme:—
No offal feeding
Offal disposal into pits
Enclosure of killing pens for human consumption
Carcase disposal
Continuous dog control
School lecture programmes.
Administratively, owners are required to present dogs for testing and to submit infected dogs to treatment. Quarantine is now imposed on those flocks where more than 20% of adult sheep have hydatids.
Progress towards eradication in Tasmania has been quite spectacular. The reduction in the percentage of infection is indicated by the following figures and they cover the period 1964-65 to 1973-74.
Dogs 11.3% to 067%
Full mouth sheep 52.2% to 7.0%.
The percentage of dog owners with infected dogs has fallen from 14.8% to 1.03%. In 1964-65 there were 19 new human cases of hydatids. In 1973-74, 6 such cases.
New South Wales
For some years, like the New Zealanders, we recommended control by asking dog owners to boil offal before feeding and to regularly treat their dogs. In retrospect, the advice though well meant, was ill advised because:—
nobody ever boiled offal for a sufficiently long period to ensure sterility of the cysts.
treatment then meant using arecoline. This drug works by purging dogs. In 25% of cases it does not work and in research after even 5 days 90% of dogs had been freed of worms.
Without a preventive programme, dog owners were in effect being lulled into a false sense of security.
Subsequently there have been a number of attempts to set up local eradication schemes, generally under the auspices of local councils. These programmes have normally been soundly based but the local committees have not as a rule remained intact for adequate periods of time and the campaigns have tended to lapse.
In a discussion of what we ought to attempt in this State, it must be accepted that because of the size of the continent the extensive movement of stock to abattoirs and the present difficulties in tracing sheep to their origin, an extensive campaign of the Tasmanian pattern is impracticable.
Unquestionably there is a need for an adequate education programme for the whole community and not just for rural dwellers. Few people who fully understand the parasite, its life cycle and the disease that it causes could remain indifferent to a programme of prevention of infection.
It has been shown quite dramatically in Tasmania that the following programme is effective:—
No offal must be fed.
Home killing should be in a dog-proof area offering offal disposal facilities.
Dogs must be kept under control at all times, either on an exercise wire or in yards and not be allowed to roam. When used for mustering the dogs should be muzzled if carcases of dead sheep are available to them.
It should always be made clear that visiting dogs are not welcome.
It is essential to dispose of carcases, especially of sheep and if there is any delay in completing this operation the carcases should be sprayed with sump oil to deter consumption. Do not feed dogs on marsupials, as many are heavily infected.
Treat dogs for hydatid tapeworms when the programme is introduced and 3 weeks after they may have been extensively exposed to infection. It is essential, however, to realise that treatment alone provides inadequate protection.
There are several basic aspects to this programme which cannot be over-stressed.
a). It is possible to keep your dog free of infection no matter how many hydatids may be present initially in your sheep. On the other hand, one feed of offal or access to one dead sheep per year could make your dog dangerous.
b). The risk of infection in man is one related to the dog and only the dog.
c). It is essential to follow the programme list in its entirety. One cannot cover up weaknesses in the programme by carrying out occasional treatment.
What about other tapeworm diseases? The Tasmanians have practically eradicated hydatids but the incidence of other conditions related to dog tapeworms has not been markedly reduced. The risk of sheep measles can be eliminated if dogs are not fed raw sheep meat. If shanks, neck or flap of sheep is to be fed to dogs it should be fully cooked in the kitchen. Access to carcases might also be important in infecting dogs with Tenia ovis the tapeworm causing sheep measles. The other tapeworm in which we are interested is Tenia hydatidgena. This tapeworm is acquired by eating offal of sheep suffering from Cysticercus tenuicollis, or bladder worn cysts. In Tasmania, inspectors believe that dogs frequently become infected because of access to carcases.
To summarise, it is essential in any eradication programme that measures be taken conscientiously and continually against infection for a prolonged period. It is inevitable that a phase of compulsion will be needed to deal with those owners who do not fulfil their responsibilities but there is no intention of endorsing such measures at this time. The introduction of a traceback capability for sheep is envisaged and when introduced it will be possible to concentrate on those holdings where infection rates are highest.