Biological Therapy 



140 



Hog Cholera 



This is an acute septicemia to which only swine are sus- 

 ceptible. 



ETIOLOGY. The exact cause of hog cholera is not 

 known. The blood of affected individuals contains the in- 

 fectious material and will reproduce the disease when in- 

 jected into susceptible swine. If such blood be passed 

 through Berkefeld filters, the filtrate is infectious, hence we 

 say that the causative agent is an ultra microscopic or fil- 

 terable virus. 



SYMPTOMS. In the fulminating type symptoms and 

 postmortem lesions may be entirely lacking and death very 

 sudden. Not infrequently this condition exists in the first 

 few animals which succumb, after which subsequent cases 

 resolve into the acute type. In the latter the incidence is 

 high, affecting practically every susceptible animal in the 

 herd, resulting in a mortality of seventy to ninety per cent. 



In the acute type the onset is gradual, the affected indi- 

 viduals being "slow" previous to the appearance of acute 

 symptoms. Later, inappetence and prostration are marked. 

 Affected animals can be made to move only with difficulty 

 and manifest a marked tendency to hide under the bedding. 

 The temperature rises four to five days after exposure and 

 ranges from 104 to 108, showing a tendency to remain high 

 rather than to fluctuate. 



Intestinal disturbances are quite regularly observed. In 

 cases tending to chronicity the appearance of pronounced 

 respiratory or intestinal disturbances indicate secondary in- 

 fection. These ore not caused by the virus of hog cholera. 



When cholera pigs are made to move two cardinal symp- 

 toms of great diagnostic importance should be observed. 

 These consist of a peculiar and typical "breaking" sideways 

 at the hock and a straightening of the ankle joint so that 

 the individual appears to be "standing on its toes." The lat- 

 ter symptom is usually the first observable in cholera sick 

 swine and differs considerably from the staggering seen in 

 many diseases or conditions and which is due to weakness. 



The period of incubation is from four to seven days, 

 while death occurs in from seven to twenty-one days. 



