462 HORSE, SWINE AND POULTRY DISEASES 



tion requires the services of an expert. The cost of hog-cholera serum 

 is considerable, usually varying from fifteen to fifty cents an animal, 

 depending upon the size. As the immunity conferred is for about 

 six months only, it is not practicable, usually, to vaccinate hogs ex- 

 cept when hog cholera is in the locality, or there is a possibility of 

 infection from other sources. The Commonwealth of Virginia sup- 

 plies hog cholera serum at cost to Virginia hog raisers through the 

 Commissioner of Agriculture, Richmond, Va., to whom application 

 for serum should be made. After an outbreak of hog cholera, non- 

 immune hogs should not be placed in the same yards or corrals, until 

 at least three months' time Has elapsed. (Va. B. 189.) 



The pig is injected subcutaneously with proper amounts of 

 serum and virulent blood. This method is used where the disease 

 does not exist or where it has just started. The immunity resulting 

 therefrom lasts longer than from use of serum alone, usually from 6 

 months to one year, or perhaps for life. There is considerable dan- 



fer from using this virulent blood method, as the practice has been 

 nown to start outbreaks of hog cholera. Veterinarians only should 

 conduct the treatment. It is not generally recommended by inves- 

 tigators at the present time. (N. J. L. S. C. Cir. 1.) 



The safety of this mode of vaccination is manifestly a condition 

 of vital importance if it is to be used in herds not already infected. 

 In the use of a living virus as a vaccine there is, necessarily, a sus- 

 picion that it may under certain conditions beget a plague instead 

 of suppressing one. A vaccine which has proved safe in its applica- 

 tion by its originators, may be very unsafe when applied indiscrim- 

 inately by farmers or even by veterinarians. (Ark. B. 105.) 



Serum Alone Inoculation. The serum-alone method, which 

 consists simply in the injection of the protective serum without the 

 simultaneous use of virulent blood, appears to confer only a tem- 

 porary immunity upon the treated pigs, unless they are exposed to 

 hog cholera a short time after receiving the serum, in which case 

 they also acquire a lasting immunity. For these reasons this method 

 is admirably adapted to the treatment of hogs in a herd where hog 

 cholera has already broken out, but which have not themselves 

 shown visible symptoms of disease. 



The experiments which are being carried out to determine the 

 curative properties of the serum are not yet complete, but from the 

 results thus far obtained we know that serum in the doses used for 

 immunization can not be depended upon to cure hogs which already 

 show visible symptoms of hog cholera. Neither the simultaneous 

 nor the serum-alone method, when properly applied, appears to in- 

 jure the hog in any way. (B. A. I. 25th A. R.) 



The hogs which are to be protected are injected on the inside 

 of the hind leg with a suitable dose of the serum alone. This injec- 

 tion will serve to protect hogs from hog cholera for several weeks and, 

 in some cases, for a longer time. But if the hog is not exposed to 

 hog cholera within a few weeks after this treatment, the immunity 

 which is conferred by the serum will gradually lessen in degree and 

 the hog may again become susceptible. If, however, the hog is ex- 



