Fig. 21.—Portion of grass stalk bearing three encysted cercariæ of the common liver fluke (Fasciola hepatica). Enlarged.
The drainage of wet pastures and the avoidance of swampy lands for grazing purposes are important measures in the prevention of fluke diseases.
Railliet and others have recently recommended the application of lime to fluky pastures, having discovered that very weak solutions are destructive not only to fluke embryos but to snails. This application is to be made during the summer months at the rate of about 500 to 1,000 pounds of lime per acre. The same authors also recommend extract of male fern for the treatment of fluke disease. Moussu states that the average dose for cattle is 1 gram of the extract for each 10 kilograms of live weight; that is, 10 grams for a young animal weighing 100 kilograms (about 220 pounds) up to 50 grams as a maximum for large animals weighing 500 kilograms (about 1,100 pounds) or more. The extract is mixed with about 5 times as much non-purgative oil and the dose is administered each morning for five consecutive days two hours before the animal is allowed to feed after having been fasted over night. The extract of male fern used should have a guaranteed strength of 22 to 25 per cent of filicine and 3.5 per cent of filicic acid.
TAPEWORM CYSTS OF LIVER AND OTHER VISCERA.
Three kinds of tapeworm cysts are found in the viscera of cattle. One of these (Multiceps multiceps, or Cœnurus cerebralis) will be further referred to in the discussion of gid ([p. 528]). All these are the intermediate stages of tapeworms, which live when mature in the intestines of dogs, wolves, and other canines. The eggs of the tapeworms are scattered over the fields in the droppings of infested dogs or wolves, and when swallowed in food or water by cattle hatch out and the embryos migrate to the liver, mesentery, lungs, brain, or other organs, where they develop into cysts, variously known as hydatids, bladder worms, water balls, etc. When organs of cattle thus infested are eaten by dogs or wolves the cystic worms are also liable to be swallowed and then develop into mature tapeworms. To prevent cattle from infection with these parasites stray dogs, wolves, and coyotes should be killed wherever found, and dogs too valuable to kill should be kept free from tapeworms. As a precaution against infection with tapeworms, the viscera of cattle, sheep, or hogs should not be fed to dogs unless cooked.
Fig. 22.—Hydatids (Echinococcus granulosus) in portion of hog's liver.