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This article was published in 1956
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
HYDATID DISEASE
(Data and comments by E. A. FARLEIGH, B.V.Sc., Inspector of Stock, Glen Innes - Inverell)
Following a recent survey of the incidence of Hydatids in sheep, cattle and pigs throughout Southern New South Wales, some alarming figures have been published.
Examinations have been conducted at abattoirs during routine meat inspection; where 300,000 sheep have shown up to 40% infection, 30,000 cattle showed 30% infection and 5,000 pigs showed 5%. The economic loss to the meat industry alone is over £600,000 per annum; due to the condemnation of livers and other portions of carcases.
The survey also revealed that 25% of dogs in these rural areas are infected with the minute tapeworm, Echinococcus granulosis. The hydatid cysts in sheep, cattle and pigs form part of the life-cycle of this worm.
It appears that, if anything, there has been an increase in the incidence of this disease over the last decade or two and this immediately causes concern to Public Health authorities, as the life cycle of this parasite can implicate humans also, and the danger to the human population, particularly in rural areas, cannot be overstressed.
The life cycle of this worm is not very complicated, and in its adult state is a minute tapeworm found in dogs, dingoes and foxes. It is only about ¼inch long and should not be confused with other much longer tapeworms found in dogs. The eggs pass out in the droppings and, for the life cycle to be completed, must then be swallowed by any of the intermediate hosts, such as sheep, cattle, pigs and man. The eggs hatch in the intestines of the host animal and the embryos penetrate the intestinal wall and are carried in the blood stream to the liver. Here some are caught up, while others may escape and be carried to the lungs or other organs, such as bone or nervous tissue. The embryo grows slowly and may after many months reach a size of up to 4 inches in diameter. These are known as Hydatid cysts, which consist of a hard capsule containing a fluid under pressure, in which are numerous tapeworm heads. To complete the life cycle these cysts must be eaten by the final host, which in most cases is the dog.
The pathogenic significance of Hydatid Disease in man is very great, though it may be some years after infection before any symptoms become evident. However, the medical profession should be the best source of advice as regards human involvement.
The methods of infection of man are several. The most likely way is the handling of dogs whose coats are contaminated by tapeworm eggs. Subsequent handling of food, rolling of cigarettes,etc., can easily transfer the eggs into the mouth. Children, who do not realise the rudiments of hygiene, show a high incidence of infection, for they commonly play around dog kennels and fondle dogs, and then suck their fingers; so easily transferring the eggs into the body. Drinking of infected water is not so important, as the eggs sink; but it cannot be overlooked. Handling sheep, whose wool is contaminated with dog faeces, is another risk.
Flies can carry tapeworm eggs on their feet and also may swallow them. Subsequent contamination of food can be brought about in this way. Stress must be laid, too, on contamination of uncooked vegetables, where dogs have access to a vegetable garden.
While all these possible sources of infection should not be forgotten, the most common means of infection of man is through direct contact with infected dogs. In certain parts of New Zealand there is one case of Hydatid Disease for every 300 people admitted to hospital.
It may be seen from the foregoing that there are two points where the cycle can be broken. The first point is to prevent the infection of dogs. If the dog does not have access to raw offal from the carcase of sheep or other animals, then it cannot consume any cysts. It is most important, therefore, not to feed raw offal to any dog. All offal should be boiled for at least 10 minutes before being fed; thus rendering the cysts sterile.
Secondly, if the dog is infected with tapeworms there are various medicants available which will eliminate the infection. Suitable drugs are Arecoline hydrobromide, Nemural and Dicestal; obtainable from chemists and stores. Regular treatment, at least every six months for rural dogs, is essential.
The education of humans to appreciate the danger of this disease is most important; and will do much to reduce the incidence in both man and animals.