EXPERIMENTS IN VACCINATION AGAINST ANTHRAX. 13 



TEST OF THE SIMULTANEOUS METHOD ON CATTLE AND SHEEP. 



A series of experiments was conducted at the experiment station of 

 the Bureau of Animal Industry at Bethesda, Md., to establish the 

 efficiency of the simultaneous method of anthrax immunization on 

 cattle and sheep. 



For this purpose 6 head of cattle and 5 sheep were given the simul- 

 taneous injection of anthrax serum and spore vaccine. Three weeks 

 subsequent to immunization they were subjected to infection tests 

 which consisted of a subcutaneous administration of 0.25 c. c. for the 

 cattle and 0.125 c. c. for the sheep of blood from a guinea pig which 

 had died from an artificial infection with our most virulent strain of 

 anthrax. 



The microscopic examination of the blood of the guinea pig showed 

 it to be heavily charged with anthrax bacilli, but in order to make 

 the test as severe as possible it was deemed advisable to use such exces- 

 sive amounts. Three additional cattle and two sheep were used as 

 checks, receiving only the virulent blood. As a result of this infec- 

 tion all animals manifested an elevation of temperature ranging from 

 103° to 107° F. The control animals especially were markedly 

 affected with typical manifestations of anthrax and all succumbed 

 within two to eight days following infection. All but one of the 

 vaccinated sheep succumbed to anthrax, but at a later date than the 

 check animals. Of the immunized cattle a marked temperature reac- 

 tion was noted, but all of these animals recovered with the exception 

 of a small, undersized, weak calf, which died in six days following 

 infection. 



While in the above test the sheep succumbed and one of the small 

 calves died of anthrax, nevertheless the potency of the serum was 

 demonstrated. The excessive virulent blood used for the infection 

 was extraordinary and could not be compared with the amount of 

 virus taken by a susceptible animal in cases of natural infection. 



FIELD TESTS. 



On June 21, 1915, Dr. R. R. Ashworth, a dairy inspector for the 

 District of Columbia, notified our office that a number of deaths 

 among hogs were occurring on a farm in Maryland, just outside of 

 the District. The symptoms described by Dr. Ashworth pointed sus- 

 piciously to anthrax. A visit was made to the farm the same morn- 

 ing, and after an autopsy on several animals, followed by a bac- 

 teriological examination, a definite diagnosis of anthrax was estab- 

 lished. This was later conclusively verified by animal inoculation 

 tests. 



At that time 7 shoats and 1 sows had died of the disease and 3 shoats, 

 4: sows, and 1 boar were showing symptoms of anthrax, several of the 



