PARASITES AXD PARASITIC DISEASES OF HORSES 



23 



cases may produce death. It is believed that most cases of colic in 

 horses result from such disturbances in the blood circulation of the 

 gut. If the plug forms in a hind leg it may cause a form of intermit- 

 tent lameness. Aside from the injuries described, mixed parasitic 

 infestation, known as strongylidosis, results when blood strongyles 

 occur in large numbers and in association with other species of 

 roundworms in the large gut, particularly when horses are kept on 

 permanent pastures. 



This condition is widespread in horses and is usually more injuri- 

 ous to foals and young horses than to older horses. Strongylidosis is 

 frequently mistaken for infectious anemia or swamp fever and cases 

 diagnosed as swamp fever, in many instances, have cleared up fol- 

 . lowing the removal of worms by medicinal treatment. The common 

 symptoms of strongylidosis are diarrhea, weakness, and emaciation. 

 The digestive disturbances result from the irritation to the lining 



Figure 16. — A small aneurism of the anterior mesenteric artery of the horse, 

 partly cut open to show worms and the heavy deposit of fibrin inside. 

 The "worms are immature forms of Strongylus vulgaris. Natural size 



of the gut produced by the parasites. At first the diarrhea is slight 

 and the soft manure lias a bad odor and contains poorly digested 

 food material; later the diarrhea becomes more pronounced, with 

 softer feces. The appetite, which is irregular at first, becomes poorer 

 and finally the horses are off feed. As a result of their weakened 

 condition, affected horses find difficulty in chewing, may throw out 

 mouthfuls of feed, and then reject feed altogether. This leads to 

 further emaciation which becomes very marked. As the disease pro- 

 gresses the bones become prominent, the coat becomes rough, the 

 eyes are sunken, and the animal becomes greatly weakened. 

 (Fig. IT.) With these symptoms there are marked changes in 

 various tissues and organs of the body. 



The working capacity of horses which are suffering from strongy- 

 lidosis is decreased considerably even before the symptoms become 

 very pronounced, and in the absence of treatment such horses are 

 able to do less and less work as the disease progresses. It has been 

 found that when horses are treated for the removal of parasites 

 many of the symptoms described above disappear, the animals take 



