130 ANNUAL REPORT OF THE Off. Doc. 



uiime hogs. IMimy times the blood proved to be contaminated or 

 changed so that it caused the death of several animals used for hyi)er- 

 immunization. The hog bred on the farm could be used for hvjjer- 

 immuiiizalion because the.v had a certain amount of immunity, and 

 would easily resist too mild hog cholera infection. Immunity pro- 

 duced with blood from hog cholera outbreaks in the eastern pait of 

 the State did not have the same protective properties against a severe 

 infection as when the serum was produced with virulent blood from 

 the western part of the State. There appears to be a variation of 

 viiulency which is confined to certain localities, and the serum 

 produced from such places will only protect against this particular 

 hog cholera infection. It is, therefore, the policy at present to use 

 a polyvalent virus fa virus which cimtains at least 10 to 12 hog 

 cholera vira ) from different localities. To increase the potency of this 

 virus seveial strains were added through the courtesy of Dr. \'an Es, 

 of North Dakota. 



We are now preparing virus by inoculation or by the exposure of 

 susceptible hogs in naturally infected pens. Hogs for this purpose 

 were purchased from parts of Pennsylvania where hog cholera was 

 never observed. They were at first inoculated but it was soon learned 

 that the pens were sufSciently infected to cause a natural infection. 

 Daily records of temperatures would indicate an infection, and the 

 animals were killed in agonal stage shortly before death. Their 

 blood is used at once for hyper-immunization. A careful autopsy 

 of the animal will demonstrate the severeness of the disease, and one 

 familiar with this work can readily ascertain the fitness of the virus 

 for hyper-immunization by the morbid lesions. Hyper-immunized 

 hogs are usually bled four times at intervals of ten days, the blood is 

 defibrinated, filtered and preserved with 0.5 per cent, carbolic acid. 

 From September to January over 111,485 c. c. of serum were pro- 

 duced. The mixture of diff'erent bleedings has usually been tested 

 in the way described by Dorset and DeSchweinitz. The results ob- 

 tained in the field with this serum are very encouraging. As a pro- 

 phylactic the serum proved to be of great value. The therapeutic 

 effect was not satisfactory. It must be kept in mind that hogs may 

 succumb after they have been immunized against hog cholera but not 

 to a secondary invasion which is caused by lesions in the lungs or 

 other organs. A statistical report would show better the value of 

 serum treatment if results were more faitlifully submitted. It is 

 hoped that during the coming year more interest wall be shown in 

 this phase of the work. 



The simultaneous method of treating hogs with a small dose of 

 virulent blood and serum together has been entirely dropped. Prof. 

 Hutyra claims that hog cholera is disseminated by the sero-simultan- 

 eous method, and that areas of the disease are thus established. His 

 views have been confirmed by our experience. If the serum treatment 

 is given early in the disease and particularly w^hen only one or two ani- 

 mals have succumbed the results are perfect. Outbreaks of hog cholera 

 should be reported as early as possible, and treatment begun at once if 

 the fullest benefit is to be expected. The serum treatment should not 

 be given unless there are cases of cholera on the premises. 



An investigation concerning the importance of the bacillus suijiesti- 

 fer and other micro-organisms found in hog cholera has been started, 

 but sufiScient data is not at hand to permit a conclusive statement. 



