Fig. 17.—Piece of lining of fourth stomach, showing cysts of the encysted stomach worm (Ostertagia ostertagi).
This parasite is as thick as a fine hair and less than half an inch in length. It lives in small cysts in the wall of the fourth stomach (fig. 17) and is also found free in the cavity of the stomach. When numerous, these parasites cause a thickening of the stomach wall and disturb its digestive functions. The symptoms caused by this parasite are very similar to those produced by the twisted stomach worm. The life history of the encysted stomach worm is not known in detail, but it is undoubtedly very much the same as that of the twisted stomach worm. The same measures as recommended above for preventing infection with the twisted stomach worm should be used. Medicinal treatment would seem to be of little use, owing to the protected position in which the parasite occurs.
INTESTINAL PARASITES.
TAPEWORMS.
Fig. 18.—A tapeworm (Moniezia planissima) which infests cattle.
Two species of tapeworms (fig. 18) are known to occur in the small intestine of American cattle. They sometimes grow to a length of several yards and to a breadth of three-fourths of an inch. Small portions of tapeworms, consisting of one or more segments, are occasionally seen in the droppings of infested cattle. The life history is not known, but the infectious stage is undoubtedly taken in with the feed or water, infection being spread by the eggs of the parasite contained in the feces of infested animals. The eggs are perhaps swallowed by some small creature (an insect, worm, or snail) which acts as an intermediate host, and which when accidentally swallowed by a cow while grazing or drinking carries with it into her stomach the infectious stage of the tapeworm.
Adult cattle do not seem to suffer much from infestation with tapeworms, but in calves these parasites may cause scouring and emaciation.
Treatment.—Medicinal treatment for tapeworms in cattle is usually unsatisfactory, but the bluestone treatment used for stomach worms and mentioned above ([p. 522]) sometimes expels tapeworms. Arsenic in doses of 1½ to 3 grains has been claimed to give good results in the treatment of calves for tapeworms. From results obtained at the Oklahoma Experiment Station in the treatment of tapeworms of sheep it would appear that the efficacy of the bluestone treatment against these parasites may be increased by the addition of tobacco. For use on cattle the bluestone and tobacco mixture may be prepared as follows: 13 ounces of snuff or powdered tobacco is soaked over night in about 8 gallons of water. To this decoction is added 1 pound of copper sulphate which has been dissolved in 2 or 3 quarts of boiling water. Sufficient water is then added to the mixture to make a total of 9½ gallons. The doses of this solution are the same as for the simple copper sulphate solution, described on [page 522], namely: