ANIMAL PARASITES OF CATTLE. 535 



blood vessels. According to Noe, they are spread from one animal 

 to another by stable flies (see p. 511). The roundworms found oc- 

 casionally in the anterior chamber of the eye (see p. 536) are per- 

 haps immature forms of this species which have reached this location 

 during their migration. 



LUNG WORMS. 



Lung worms {Dictyocaulus viviparus, fig. 29) 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 advo- 

 cated for lung worms, including fumigating with different substances 

 and injections of remedies into the 

 trachea by means of a large hypo- 

 dermic syringe or by a special 

 spraying apparatus, but none has 

 been very successful from a prac- 

 tical standpoint. About all that 



can be done is to feed affected ani- Fig. 29. — Lung worm (Dictyocaulus vivi- 

 Tnilq wpll nnd nrnfprt thpni frnm Parus) of cattle. Outlines showing nat- 



mais wen ana protect inem rrom ^^.^j ^j^^ ^^ ^^^j^ (above) and female. 

 exposure, removing them from the 



pasture and keeping them in dry yards or stables maintained in a 

 cleanly, sanitary condition. 



The methods of prevention in general are similar to those described 

 under the discussion of the twisted stomach worm (p. 526). 



PARASITES OF THE BLOOD. 



Certain flukes (Schistosoma bovis and related species) which live 

 in the blood vessels (the large veins) of cattle in tropical and sub- 

 tropical countries cause bloody urine and diarrhea, the feces being 

 mixed with blood. These parasites have not yet been discovered in 

 the United States, although the natural conditions are such in some 

 parts of the country that they are liable to become established if 

 introduced. 



The embryos of Setaria labiato-papHlosa (p. 534) which occur in 

 the blood may be found by microscopical examination. They ap- 

 parently cause no trouble. 



The organism which causes Texas fever is a protozoan parasite 

 {Piroplasma higeminum) of microscopic size, which lives in the blood 



