18 MASS. EXPERIMENT STATION BULLETIN 295 



GLOACAL VERSUS BURSAL VACCINATION 



Forty chickens, three and one-half months old, were divided into two groups of 

 twenty each. Group 1 was inoculated in the cloaca and Group 2 in the bursa of 

 Fabricius. In Group 1,8 of the chickens developed mild inflammation of the cloaca, 

 which indicated 40 per cent successful takes; while 18, or 90 per cent, of those in- 

 oculated in the bursa of Fabricius showed definite indications of takes. Two 

 chickens from each group contracted infectious laryngotracheitis and died. When 

 tested for immunity fourteen days later, 10 of the chickens in Group 1 contracted 

 the disease and 6 died, while all of the 18 living chickens in Group 2 resisted infec- 

 tion. 



This experiment indicates that the number of takes is greater when the bursa 

 of Fabricius is inoculated than then the cloaca is swabbed with the same virus in 

 the same manner, and the resulting degree of immunity is greater in the former 

 than it is in the latter case. 



DISCUSSION 



In attempting immunization in infectious laryngotracheitis the object should be 

 to produce an immunity at least as good as that which follows the disease when 

 naturally contracted. At present this can not be accomplished artificially. Since 

 birds infected in the larynx and trachea are liable to die of asphyxia, due to plug- 

 ging of the respiratory tract with pseudoniembrane, the infection should be kept 

 from this system, unless partial immunity has been previously produced by means of 

 properly filtered tracheal exudate or hyperimmune serum. Laryngotracheitis is 

 primarily a disease of the mucous membranes and infection is not induced by 

 inoculation of the virus into the subcutaneous tissues or blood stream. However, 

 when a relatively large dose of the virus is released in the blood stream, the in- 

 fectious agent may be carried to the larynx and trachea and a natural attack 

 result. On the other hand, when the virus is introduced into the blood stream in 

 relatively small quantities over a comparatively long time, active immunity is 

 produced. It seems to make little difference whether the small quantities are 

 continuous, as they probably are in the bursa of Fabricius infection, or intermit- 

 tent as in intravenous inocalation. 



Naturally acquired immunity in infectious laryngotracheitis is permanent, 

 while artifically acquired immunity is relative and appears to depend upon the 

 severity of the reaction. Hence the introduction of filtered tracheal exudates 

 into the blood stream, or the inoculation of a mucous surface outside of the trachea 

 such as the bursa of Fabricius, stimulates various degrees of active immunity. 

 The inoculation of hyperimmune serum into the blood stream produces passive 

 immunity only, because the antigen is not present, and the tissues of the bird are 

 not stimulated to produce antibodies. It is impossible to control the reaction in 

 any of the methods suggested for the immunization of birds against infectious 

 laryngotracheitis, because a standard vaccine has not been produced, and in spite 

 of the arbitrary standard suggested in this bulletin for inoculation in the bursa of 

 Fabricius, the danger of spreading the infection where it does not already exist is 

 involved. 



Birds weakened, as in coccidiosis, are liable to develop acute infectious laryngo- 

 tracheitis when vaccinated in the bursa of Fabricius and relatively large numbers 

 die. The simultaneous vaccination of birds against infectious laryngotracheitis 

 and chicken pox was not attempted in these studies, because the experiments 

 were conducted in the laboratory, and it was not considered expedient to 

 make the two tests under such limitations, for fear that the results might 



