460 HORSE, SWINE AND POULTRY DISEASES 



of a cholera pig of equal weight to hyper-immunize every pig used 

 for the production of hog cholera serum, some idea of the cost is at 

 hand. Other expenses are losses from death of pigs producing hog 

 cholera blood before they are bled ; also from death of pigs used to 

 test potency of the serum produced before it is sent out for use. 

 (N. J. L. S. C. Cir. 1 ) 



At the present time it is impossible to state definitely just what 

 the cost of this serum should be. This will undoubtedly vary in dif- 

 ferent localities, depending upon local conditions, such as the price 

 of hogs, the cost of feed, and similar minor considerations; but it 

 has been estimated, and this estimate has been confirmed by at least 

 one of the States now conducting this work, that the serum can be 

 made for 25 cents a dose. We do not regard this as the minimum 

 limit of cost for the serum production, but rather hope that with in- 

 creased knowledge of the disease and wider experience with the serum 

 production this estimate will be materially reduced. (F. B. 379.) 



It is gratifying to be able to state positively that epidemics of 

 hog cholera can now be successfully controlled by a process of vacci- 

 nation. (Tenn. B. 85.) 



Two Methods of Vaccinating. The first method is to use the 

 serum alone. In this method there is simply injected into the mus- 

 cles of the hog a dose of the anti-hog cholera serum, which makes 

 the hog immune against cholera for a time varying from a few weeks 

 to several months. This is the method used when, for instance, a 

 very fat show herd is vaccinated. It is absolutely safe. It is also 

 used in herds where the cholera already exists and some of the ani- 

 mals have been exposed only a few days. After the disease has been 

 in a herd for three or four days, vaccinating seldom does any good. 

 Thus the earlier the vaccination in these cases the more certain the 

 results. A day's time here may mean either the losing or saving a 

 large part of the herd. 



Where vaccinating is done in diseased herds, the amount is in- 

 creased from one-half to double the regular sized dose. The second 

 method is one in which there is some danger, but the results, if the 

 animal survives, renders it immune for the rest of its life. It is the 

 so-called serum simultaneous method, in which there is injected at 

 the same time, in addition to the serum, a small amount of virulent 

 blood or blood taken from a hog very sick with the cholera. This 

 method really gives the hog a very slight form of the disease and as 

 a consequence the animal does not take the cholera the second time 

 it has been artificially immunized. This is the most satisfactory 

 method to use in a healthy herd, or before they become infected. 

 Great care is necessary that too much of the virulent blood is not 

 used. If the dose is too large the result may make the hog quite 

 sick, or even cause death. (Kan. B. 163.) 



The serum alone method produces an immunity lasting 3 to 6 

 weeks, the one in which the serum is used in conjunction with 2 to 

 3 cc. of fresh blood obtained for a hog sick with hog cholera, known 

 as the serum-simultaneous method, produces an immunity which is 

 considered practically permanent. When injecting in the second 



