LARYNGOTRACHEITIS VACCINATION 11 



the exudate from 12 infected pullets and cockerels. On the 14th, 284 birds were 

 vaccinated before the work had to be given up on account of rain. The vaccine 

 left over from the birds that had been slaughtered was used to inoculate 12 more 

 culls in order to insure a fresh supply of virus for use later. The rain continued 

 until the afternoon of the 17th. The next day was fair and the remaining 1,200 

 birds were vaccinated with fresh liquid vaccine prepared from the last lot of 

 inoculated culls. 



During the three rainy days the unvaccinated birds were in a field about 50 

 yards from the last lot of vaccinated pullets. Largely on account of the rain 

 the birds stayed in the colony houses most of the time. One colony house of 

 125 cockerels was more active than the pullets, and it was noticed that some of 

 these cockerels were showing symptoms of infectious laryngotracheitis on the 

 day the vaccination was recommenced. Some of these cockerels had natural 

 outbreaks of infectious laryngotracheitis and some died. The other birds came 

 through the year without incident. 



Flock 5 



This flock was not vaccinated, but it is closely related to the field experiments, 

 and demonstrated far more conclusively than any set laboratory experiment 

 possibly could the existence and dangers of carriers in vaccinated flocks. The 

 history of this flock is somewhat vague and indefinite because records were not 

 made at the time developments occurred, but it is sufficient to indicate the 

 points suggested. 



Flock 5 was visited February 9, 1934. Many of the hens showed active symp- 

 toms of infectious laryngotracheitis and some were dying. The caretaker re- 

 ported that he was carrying out 15 or 20 dead hens per day. The roosters had 

 swollen wattles and combs, but this appeared to be due to freezing and secondary 

 infection. Cholera was excluded from the diagnosis by bacteriological examina- 

 tion of both roosters and hens. Two of the roosters were sick from the absorption 

 of toxins from the edematous wattles, and one was reported as having died. The 

 two sick roosters had been taking severe punishment from the others and were 

 in bad shape. However they recovered in 24 hours after being removed from the 

 flock and having the combs and wattles lanced. 



The first lot of roosters had been purchased December 24, 1933, and the next 

 lot two weeks later, or January 6, 1934. Infectious laryngotracheitis appeared 

 soon after the second lot of roosters was added to the flock, although the exact 

 date of the beginning of this outbreak is unknown. The pullets. 500 in number, 

 had been purchased from a flock that has never had infectious laryngotracheitis. 

 The evidence was against the roosters. Consequently the 64 living roosters were 

 tested for carriers by inoculating exudate from the larynx and trachea into the 

 larynx and trachea of susceptible chickens. Two susceptible chickens were 

 inoculated from each rooster. This made a total of 128 chickens on the test. 

 Of these chickens 124 remained healthy for 10 days, and four died from two of 

 the roosters, one on the fourth day, two on the fifth, and one on the sixth. The 

 test was repeated two weeks later with the same results, except that all four 

 of the chickens were found dead on the fourth day. 



The results of this experiment indicate that two chronic carriers of infectious 

 laryngotracheitis were sold into a healthy fleck as a result of the purchase of 

 vaccinated birds. Of course it may be argued that this might have happened 



