To prevent cattle from becoming infested with this parasite care should be taken that human feces are not placed where they will contaminate the feed or drinking water.
This parasite is very common in cattle in the United States, at least 1 per cent being infested. As a result considerable loss is entailed through condemnations of beef carcasses by meat inspectors, because of the presence of tapeworm cysts. All this loss could be avoided and the danger of tapeworm infestation in human beings from this source could be removed by the observance of proper precautions in disposing of human excreta. At the same time much sickness and many deaths from diseases (hookworm, typhoid fever, etc.) caused by soil pollution would be prevented, and farm life would be rendered much safer than under the poor sanitary conditions which are responsible for the high percentage of tapeworm cysts among cattle in the United States.
THREAD WORMS IN THE ABDOMINAL CAVITY.
Thread worms (Setaria labiato-papillosa) 2 to 4 inches long are frequently found in the abdominal cavity. They seem to cause little or no trouble. The embryos produced by these worms enter the blood vessels. According to Noé, they are spread from one animal to another by stable flies (see [p. 503]), but this has not been definitely proved. The roundworms found occasionally in the anterior chamber of the eye (see [p. 531]) are perhaps immature forms of this species which have reached this location during their migration.
LUNG WORMS.
Lung worms (Dictyocaulus viviparus, fig. 24) in cattle are thread-like worms 2 to 4 inches long, found in the bronchial tubes and producing a condition known as verminous bronchitis. The life history of the parasite is not fully known, but infection is evidently derived through the medium of pastures where infested cattle have grazed. In the later stages of the disease the cattle cough, especially at night. Young cattle are more seriously affected than old animals.
Treatment for lung worms.—Various treatments have been advocated
Fig. 24.—Lung worm (Dictyocaulus viviparus) of cattle. Outlines showing natural size of male (above) and female.