Page:Popular Science Monthly Volume 23.djvu/767

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THE LIVER-FLUKE OF SHEEP.

it is well to use the lime to destroy snails which may have been brought down from infested areas.

If there is suspicion that a lowland is likely to give the "rot" to sheep, the best plan is to not allow them to feed upon it. In seasons of excessive moisture it may be impossible to keep the flocks on dry pastures. Salt, as a preventive, may be used in a second way. It acts injuriously upon the germs when fed to the sheep, and it also improves the general health of the animal. In addition to the salt, use dry feed as much as possible. The sheep should not be allowed to graze too closely, for the snails, as a rule, keep near the ground.

If all farmers would unite in carrying out the above preventive measures given by Professor Thomas, the losses from a fatal disease would be greatly reduced. Rabbits and hares are an obstacle to the total extermination of the "rot" in sheep.

The literature of the liver-rot in sheep is specially interesting in the light of our present knowledge. Jennings, in his work on "The Horse and other Live-Stock" (1866), says: "The malady is unquestionably inflammation of the liver. These fluke-worms undoubtedly aggravate the disease and perpetuate a state of irritability and disorganization, which must necessarily undermine the strength of any animal. . . . The sheep, having a little recovered from the disease, should still continue on the best and driest pasture on the farm, and should always have salt within their reach." Youatt, in his work on sheep, in 1848—back of which date it is not worth while to go—wrote at length upon the "rot." He located the disease in the liver, and states that it has existed from the earliest period of agricultural history. His description of a diseased sheep was full and quite accurate, but the cause was unknown to him. He says, without qualification, that it is inflammation of the liver. The full-grown fluke is too large an object to escape notice in the examination of an infested liver, and therefore was known to Youatt and the veterinarians of his day, but was considered the consequence instead of the cause of the "rot." They believed that the "rot" was connected in some way with the soil, it being confined to wet seasons and to sheep which fed on marshy lands. "It has reference to the evaporation of water, and to the presence and decomposition of moist vegetable matter." In other words, the gases arising from decomposing organic substances cause the "rot." Randall, in his "Sheep Husbandry," states that this view at that date (1860) was universally received by scientific veterinarians. H. Clok, V. S., in his "Diseases of Sheep" (1869), says the "rot" is analogous to "fluke," and is produced by many causes, among which "grazing on marshy or sour meadows" is a leading one. In speaking of the fluke, he says, "The worms are found spontaneously, like all other worms of the viscera, and the opinion that they are introduced into the body with the food, drink, etc., must be considered erroneous."

With the first symptoms of the liver-fluke in sheep there is a tend-