272 PARASITES OF THE DOMESTIC ANIMALS 



is especially prevalent in the Mississippi Valley, in the region of rivers 

 tributary to the Mississippi, and in the Gulf States. In parts of the 

 Middle West and South the parasite has been such a source of discour- 

 agement as to cause the sheep industrj^ to be almost completely aban- 

 doned. 



Pathogenesis. — Taken up as larvae with ingested plants or drinking 

 water, the worms attack the mucosa of the fourth stomach and feed 

 upon the blood of their host. The degree of disturbance which they 

 cause will be proportionate to their number. Heavy infestations are 

 accompanied by disorders of digestion and lead through loss of blood 

 to anemia, dropsy, and emaciation, the general morbid effect being 

 contributed to by the toxins elaborated by the parasites. 



Symptoms. — The symptoms are those of a pernicious anaemia. The 

 infected animal becomes dull and spiritless and there is arrested develop- 

 ment. The appetite is diminished and depraved, and the animal fre- 

 quently seeks water to quench an intense thirst. The anaemia is revealed 

 in the paleness of the skin and visible mucous membranes and in the 

 edematous swellings in dependent parts of the body, often under the 

 lower jaw. Later in the course of the disease a diarrhea appears with 

 watery dark discharge of putrid odor. In some cases the toxic disturb- 

 ances may be manifested by convulsions or paralysis. Finally, after a 

 course of several months, the animal dies in a state of extreme emacia- 

 tion and weakness. 



The cause of these symptoms of a progressive anaemia can often be 

 no more than suspected, and, where the condition prevails in flocks, a 

 more certain diagnosis may be made by killing an affected animal and 

 examining the fourth stomach. 



For Post-mortem Appearance, Development, Control, and Treat- 

 ment, refer to pp. 275-279. 



Gastro-Intestinal Strongylosis of Cattle 



Several species of strongyles may occur in the abomasum of cattle- 

 Of these the most important are Hcemonchus contortus, described under 

 gastro-intestinal strongylosis of sheep, and the encysted stomach worm, 

 Ostertagia ostertagi. 



1. Ostertagia ostertagi (Strongylus ostertagi). Fig. 14L Tricho- 

 strongylinae (p. 268). — The body is filiform with attenuated extremities. 

 The mouth is small and surrounded by six indistinct papillae; cervical 

 papillae present. The cuticle has 25 to 35 longitudinal lines or ridges. 

 The bursa of the male is comparatively small and has two lateral lobes 

 united by a small median lobe (Fig. 142) . The spicules are short, each 

 having two slender barbed processes coming off from the inner side in 

 the posterior half. The vulva of the female is a transverse slit covered 



