210 , TECHNICAL BULLETIN 10 



Virus C presented an incubation period of nine days, niaxinuini develop- 

 ment fifteen days later, and complete recovery within an additional six days. 



Virus D was very weak. The period of incubation was twelve days. There 

 was practically no further development of pox and recovery soon took place. 



Interpretation. 



The degree of efficiency of the powdered pox virus vaccine depends upon 

 the potency and antigenicity of the virus of which it is composed. The fol- 

 lowing conclusions are then evident: — 



1. The viruses, being non-uniform in potency, would produce vaccines of 

 varying efficiency. 



2. A method of standardizing the virus and vaccine, which is lacking at 

 the present time, would be essential to the efficiency of the vaccine. 



3. An autogenous virus would produce a vaccine of greater value than one 

 composed of a stock virus. 



The Efficiency of Powdered Pox ^']uus Vaccines. 



The powdered pox virus vaccine was first used by Manteufel (15) and 

 by Hadley and Beach (16). The vaccine as commercially distributed to-day 

 is a development of the original methods of these workers. 



Scabs collected from pox nodules are the source of the virus. In order to 

 produce large quantities of scabs it is necessary to maintain a flock of young 

 cockerels, preferably white leghorns. The combs and wattles are scarified 

 and the powdered scab virus after being "emulsified" in physiological salt 

 solution is vigorously rubbed into the wounded areas. Typical pox scabs will 

 develop and mature on susceptible birds in from seven to twelve days. The 

 scabs are then collected, thoroughly dried, ])assed through a coffee mill, and 

 finally pulverized in a ball mill. The product is stored away as the stock 

 virus. 



The vaccine is made by takinsr 1 erram of the powdered virus and thoroughly 

 triturating it in 100 cc. of physiological salt solution. It is then attenuated 

 at 55° C. for one hour in a water bath. Finally it is filtered through sterile 

 cheesecloth into vaccine bottles, and after cooling is ready for use. The entire 

 procedure should be handled in as sterile a manner as possible. The vaccine 

 should be used within ten to fifteen days after it is manufactured because it 

 deteriorates rapidly. 



In the following experiments having to do with the efficiency of the powdered 

 pox virus vaccines each bird was housed in a separate compartment. The 

 final conclusions are based on a repetition of experiments and the average 

 reaction of a group of birds. The vaccine used was manufactured as described 

 by J. R. Beach (17), a brief description of which is given above. 



Experiment 1. 



Part A. 



A freshly made vaccine, composed of virus B, was administered subcutane- 

 ously to a group of six healthy birds, 1 cc. being given to each bird beneath 

 the skin of the breast under the right thigh. The group was divided into three 

 lots of two birds each. 



Lot 1. Fourteen days after vaccination both liirds were inoculated on comb 



