Table 3. Results of Newcastle Spray at Farm No. 1 



Age 4 weeks 8 weeks 12 weeks 



Geometric mean litre 1.111 7.464 7.127 



At ten weeks of age, two groups of ten Ijirds were withdrawn for chal- 

 lenge purposes. One group was challenged with 1000 infective doses of a 

 held strain of infectious bronchitis, employing .2 cc. intratracheally. One 

 bird showed respiratory symptoms against challenge. In the other group, 

 wdiich was challenged with the Boney strain of Newcastle virus, two birds 

 showed paralysis. 



The mortality from all causes on the 100.000 liroilers was 2.3 per cent 

 for three weeks following vaccination. 



According to serological test, adequate parental immunity was present 

 in chicks hatched from the spray-vaccinated parents. These chicks were 

 spray-vaccinated, showing a geometric mean titre of 16.14 at day-old, with 

 95.0 per cent of the samples tested for bronchitis antilxxlies. neutralizing 

 100 or more neutralizing doses of an embryo-adapted bronchitis virus. 



During the past two years over 3,000,000 birds have been vaccinated 

 in the State of New Hampshire, with over 200 individual farms having been 

 involved. The size of the flocks ranged from 100 to 100,000 chicks. 

 Brooding systems of various types were used on these farms. Management 

 conditions of all types were also encountered. The age of the chicks ranged 

 from 1 to 7 days at the time of vaccination. 



The mortality figures on the entire number of birds sprayed averaged 

 2.4 per cent. This figure includes losses from all causes, not merely losses 

 resulting from the vaccination alone. At one period during the fall and early 

 winter of 1953, the average mortality was 3.1 per cent, but a change in the 

 technique at that time lowered the mortality figures. The figures for the 

 three months following presented an average mortality from all causes of 

 1.9 per cent. 



The symptoms appeared on an average of three days post inoculation. 

 Such symptoms were generally mild and, in isolated instances, went un- 

 noticed. The average length of symptoms was approximately 17 days. 



Blood samples, taken at the time of vaccination, and at 4-week intervals 

 thereafter, exhibited the following geometric mean ])attern. (Samples 

 labeled as day-old may actually be from 2- to 3-day-old chicks, but in all 

 instances they are pre-inoculation titres.) 



Table 4. Results of Newcastle Spray When in Combination with Infectious 



Bronchitis 



(Pre-Inoc.) 

 Age Day-Old Weeks 



4 5-8 9-12 13-16 16-19 20-f 



Gcometric mean titre 15.32 7.52 6.97 8.82 121 4.34 18.24 

 Positives 86.8% 76.7% 72.57^ 73.0% 75.67c 70.5% 91.8% 



'o 



Serum neutralization tests for Newcastle disease antibody, while of 

 necessity very limited, demonstrated that 76.8 per cent neutralized 100 or 

 more neutralizing doses of an embr}o adapted Newcastle virus strain at 16 

 weeks of age. 



12 



