IMMUNOLOGY OF LARYXCOTRACHEITIS 9 



the day symptoms appeared; those in Group 2 received 1/2 cc. on the same day 

 and 3/4 cc. on the day following; while those in Group 3 were treated with 1 cc. 

 of hyperimmune serum two days after symptoms appeared. The results of this 

 experiment are tabulated as follows: — 



Table 6. — The Results of Intravenous Inoculation with Hyperimmune 



Serum 



Treated with Controls 



firoiip virus and hyperimmune serum (virus but no serum) 



Affected Affected 



Recovered Died Recovered Died 



1 8 2 4 



2 10 t 3 

 .3 2 8 4 



Totals 



Table 6 indicates that one large dose of the hyperimmune serum on the day 

 symptoms appear is not as effective as smaller doses given twenty-four hours 

 apart. Serum administered intravenously two days after symptoms have already 

 appeared, or in other words when the disease is pretty well advanced, is of little 

 value. All of the birds protected by the hyperinmiune serum and recovering 

 from the intratracheal inoculations were found to be immune a month later. 

 The reaction in these partially immune birds may have been similar to the serum 

 and virus immunization process so often taken atlvantage of in hog cholera, rinder- 

 pest, and sometimes in dog distemper. 



The task of inoculating birds intravenously was slow, painstaking labor, be- 

 cause each bird had to be treated individually and the needle carefully man- 

 euvered into the wing vein. For this reason it was almost impossible to inocu- 

 late successfully birds under three months of age. Since infectious laryngo- 

 tracheitis is primarily a disease of chickens, this method may not be practical on 

 a large scale. 



Subcutaneous Inoculations 



In order to determine the eflicacy of the subcutaneous inoculation of hyperim- 

 mune serum, 42 pullets and cockerels three months old were divided into three 

 groups of 14 birds each, and inoculated intratracheally with infectious laryngo- 

 tracheitis virus. Then 10 birds in each group were treated subcutaneously with 

 hyperimmune serum, and 12 controls, 4 for each group, were not given any serum. 

 The doses of serum for each group varied as follows:- 



Group 1 received 1 cc. of serum on the day the tracheas were inoculated, and 

 a second dose was given twenty-four hours later on the other side of the breast. 

 Group 2 was inoculated in the same manner, e.xcept that the inoculations were 

 commenced the second day after symptoms appeared. Group 3 was given 1 cc. 

 of hyperimmune serum only on the day symptoms of infectious laryngotracheitis 

 appeared . 



In these experiments the hyperimmune serum apparently filtered slowly into 

 the tissues and did not neutralize the virus of infectious laryngotracheitis to any 

 great extent. The best results were secured in Group 1 in which chickens were 

 inoculated before symptoms of disease appeared. All of the surviving chickens 

 were found to be immune a month after recovering from the disease, except the 

 controls and two unaffected chickens in Group 1. The controls died, but the two 

 unaffected chickens in Group 1 recovered. 



