Diagnosis. Early diagnosis is difficult, and can only be established by microscopic examination of the excreta and the discovery of eggs. On an average one may find one egg in each preparation when the liver contains 80 to 100 flukes. When wasting is very marked, and particularly when there has already been a number of deaths, diagnosis becomes extremely easy. It is sufficient to find flukes in any form (Distoma hepaticum rel lanceolatum) to be assured as to the cause of disease.
Prognosis. In severely infested cases the prognosis is extremely grave, because no efficient method of treatment exists. Embedded in the liver, the parasites resist the action of all drugs, and we know of no anthelmintic eliminated by the bile which in any way affects their vitality. When the disease is recognised early, the most economical method is to fatten the animals as rapidly as possible and prepare them for slaughter.
Treatment. There is no reliable curative treatment. The drugs which one might employ would kill the animal before poisoning the parasites embedded in the liver. Various mixtures containing sulphate of iron, juniper leaves, etc., have been recommended; but rich food constitutes the best of all treatment, both from a curative and a prophylactic standpoint.
With the view of preventing the disease, however, and protecting flocks from attack in places where the disease is common, certain precautions should be adopted. They comprise—(a) providing a free supply of rock-salt, either in masses placed in the mangers or distributed with the food; the salt increases gastric secretion, and has a slight action on the parasites: (b) adding to the food during the first months of winter branches of birch, juniper, willow, and broom; the leaves of these plants contain aromatic or resinous principles which act on the liver, are eliminated by the bile, and may have valuable results.
But of all preventive measures the most effective consist in draining, cleansing, and drying low, moist, or marshy lands, because the molluscs which are essential to the life cycle of the parasites are unable to develop where the soil is dry. The manure containing the eggs of the parasites may be disinfected by adding to it lime, sulphate of iron, or common salt. Common salt and lime spread over the pastures has a double beneficial influence, acting both as a manure and as a parasiticide. From May to August is the best time for spreading this dressing.
The fluke embryos are destroyed by 1 to 2 per cent. solutions of common salt, and by ¾ per cent. solutions of lime.
In over-stocked fields the animals are obliged to graze very close to the ground, and are thus more exposed to infection. Over-stocking should therefore be avoided. Animals should not be left too long on the same ground. If infected they should at once be driven to higher pastures. Raised water tanks can be placed in the pastures—they are less likely to become infected. Animals from known infected flocks or herds should not be purchased. Livers from infected animals should be cooked or destroyed. If eaten raw by dogs the eggs pass uninjured through the dog’s intestine and infect fresh pastures.
Sulphate of iron distributed in quantities of 250 to 400 lbs. per acre is valuable as a manure, and would probably have a greater effect in destroying the embryos.