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CIRCULAR 148. U. S. DEPARTMENT OF AGRICULTURE 



that of blood strongvles. described elsewhere in this circular, with 

 respect to the development of the eggs and larvae on pastures. It is 

 also fairly certain that infestation is direct, and results from the 

 swallowing, by horses, of the infective larvae with food or water. 

 However, these worms burrow only into the stomach wall and are 

 not known to wander extensively, as young worms, throughout the 

 body of the horse. 



Symptoms and lesions. — These parasites injure the stomach wall. 

 Sometimes the stomach lining shows areas superficially like a ring- 

 worm or a mass of small tumors (fig, 5). In addition to these injuries 

 the parasites contribute to general gross parasitism in horses which 



Figure 5. — Portion of the inner lining of a horse's stomach, showing lesions 

 produced by the small stomach worm, Trichostrongylus axei. (Photograph by 

 courtesy of the Agricultural and Mechanical College of Texas.) 



is characterized by weakness, paleness of the mucous surfaces, wast- 

 ing, and digestive disturbances. 



Treatment. — It is seldom that specific treatment is employed to 

 remove or destroy these parasites. So far as is known, however, 

 the use of phenothiazine. as recommended for removing strongvles. 

 is a reasonably effective measure. There is some evidence, also, that 

 treatment with carbon disulfide, as described for large stomach 

 worms, may be effective against this species. 



Prevention. — Preventive measures are similar in a general way to 

 those discussed in connection with preventive measures against blood- 

 worms and other strongvles. The similarity in control measures is 

 based on similar life histories. 



