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 INFECTIOUS LARYNGOTRACHEITIS VACCINATION 



By Charles S. Gibbs, 1 

 Research Professor of Veterinary Science 



This bulletin is a continuation of a previous study (Gibbs, 1933b) which should 

 be consulted for a knowledge of the immunology of infectious larvngotracheitis 

 as demonstrated up to the present in laboratory and field experiments. Its 

 object is primarily to record the results of certain field experiments which were 

 conducted in Worcester and Norfolk Counties during the summer and fall of 

 1933 and the winter and spring of 1934. Before attempting the field work 

 it was necessary to make further laboratory studies in order to determine, (1) 

 what is the most satisfactory time after vaccination to read takes; (2) what per- 

 centage of takes will insure a satisfactory degree of immunity for a vaccinated 

 flock as a whole; (3) whether carriers are produced by vaccination. Other 

 laboratory experiments were necessary after the field vaccinations had been 

 completed, in the search for cloacal and bursal carriers and the study of certain 

 other diseases resembling infectious larvngotracheitis clinically. 



LABORATORY EXPERIMENTS 



The Most Favorable Time For Reading Takes 



It is known that the virus of infectious larvngotracheitis has special affinity 

 for the mucous membrane of the eye, nostril, larynx, trachea, cloaca, and bursa 

 of Fabricius. In these experiments a "take" is indicated by inflammation re- 

 sulting from the inoculation of the virus into the mucous membrane of the cloaca 

 and bursa of Fabricius. 



In order to determine the most favorable time for the reading of takes, 365 



birds of various ages were vaccinated and daily observations made. It was 



found, regardless of age, that takes were fairly evident from the third to the 



eighth day, and that the fourth and fifth days were the best for reading takes in 



^-v a vaccinated flock, as shown in Table 1. 



A Comparative Classification of Takes 



The takes recorded in Table 1 were classified into five groups as shown in 

 Table 2. From the beginning it was realized that any attempt to classify takes 

 <v in vaccinated birds would have to be on a relative basis because they would grade 

 into each other in such a manner that in many cases no sharp limits of demarca- 

 * tion would be evident. But this experiment had some real value in training the 

 eye and the judgment and in developing precision and speed in reading takes 

 under controlled conditions in the laboratory. Without this preliminary train- 

 ing, the field experiments might not have been satisfactory. 



In this study the expression "no visible takes" indicates that the virus had no 



'The writer extends his sincere thanks to Mr. John H. Vondell of the Poultry Department of 

 the Massachusetts State College, for taking the photographs showing the method of holding birds 

 for vaccination against infectious laryngotracheitis. 



