HEMORRHAGIC SEPTICEMIA 301 



most predisposed, and in them the disease assumes usually a 

 very acute form. In older sheep the disease is more chronic. 



The infective discharges of diseased animals obviously c6n- 

 tribute toward the spread of the disorder. In sheep herds 

 running in small pastures or kept crowded in folds the disease 

 assumes a very virulent form. It is transmitted to healthy 

 sheepfolds by infected animals. 



Predisposing causes are anything that will reduce the resis- 

 tance of the sheep, such as cold, getting wet by rain, etc. The 

 disease is more common in wet seasons and on low grounds. 



In all probability infection with strongyls may be a predis- 

 posing cause. 



Necropsy. — In peracute cases the postmortem is largely 

 negative, except for the symptoms noted under Hemorrhagic 

 Septicemia. 



In the acute form the subcutaneous connective tissue of the 

 dewlap, neck, and throat shows gelatinous infiltration. The 

 mucous membranes of the head, air passages, abomasum, and 

 bowel are inflamed (reddened and swollen). The lymph 

 glands are enlarged, diffusely reddened (blood-shot). Pete- 

 chia? and ecchymoses are noted in the serous membranes, 

 kidneys, and lymph glands. In many cases, even in the acute 

 form, the lungs are involved. In them are found dark, red- 

 dish-brown areas of bronchopneumonia surrounded by infil- 

 trated interlobular connective tissue. The spleen is usually 

 normal. 



In the subacute form bronchopneumonia involving the 

 anterior and lower parts of the lung is present. The pleura 

 and also the pericardium is often covered with fibrinous 

 pseudomembranes and the serous cavities partially filled with 

 a clear yellow or turbid fluid. Bronchitis and enteritis may 

 also be present and in many cases fibrinous rhinitis. 



In the chronic form larger areas of the lung and pleura are 

 involved. Thickenings and adhesions are common. The in- 

 volved area is hepatized, some areas which have undergone 

 necrosis surrounded by connective-tissue capsules. The 

 necrotic foci when cut through show a yellow centre of viscid 

 pus surrounded by concentric layers resembling in structure 

 an onion. However, in some cases none of the internal organs 



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