Biological Therapy 



151 



DIAGNOSIS. From the foregoing it will be seen that a 

 differential diagnosis is beset with many difficulties. It 

 should be arrived at only after a combined and careful study 

 of the history, sytnptoms and post-mortevi lesions. Many 

 times a real study of the history and symptoms will make 

 possible a correct diagnosis not afforded by the lesions. It 

 is seldom safe to arrive at a conclusion following one au- 

 topsy, and diagnosis had best be made only after a compila- 

 tion of the findings from several autopsies. 



When clinical diagnosis is impossible, laboratory exam- 

 inations should be resorted to. In making such an examina- 

 tion the blood is first cultured for the presence of bacteria 

 causing diseases other than cholera, after which it is passed 

 through Berkefeld filters and the filtrate injected into sus- 

 ceptible pigs. Whenever possible the blood from acute cases 

 should be used. Blood for this purpose must be thoroughly 

 difibrinated in order to prevent coagulation. 



PREVENTION. The fact that anti-hog-cholera serum 

 and hog cholera virus are the only agents capable of prevent- 

 ing this disease is too well known to require discussion. 

 There are two methods of using these products for the pre- 

 vention of hog cholera. 



1. Serum only treatment. 



2. Simultaneous treatment. 



1. Serum Only Treatment. This consists of injecting 

 anti-hog-cholera serum subcutaneously or intramuscularly 

 into susceptible swine and is followed by a temporary or 

 passive immunity lasting from three to six weeks. This 

 single or serum only treatment is indicated in the treatment 

 of young pigs, in pregnant sows close to farrowing and in 

 sick individuals. The immunity conferred by this method 

 is entirely mechanical and passive except when adminis- 

 tered to animals already infected with hog cholera. Several 

 years ago infected swine were treated by this method on the 

 assumption that the animals already had enough virus with- 

 in their system to insure active immunity after recovery. 

 Experience, however, taught that this method was not safe 

 and it largely has been supplanted by the simultaneous treat- 

 ment. 



2. Simultaneous Treatment. This consists of the sub- 

 cutaneous or intramuscular injection of liberal doses of anti- 

 hog-cholera serum (see table of dosage) and simultaneously 

 but at a different site two or more cubic centimeters of hog 



