Most of the birds were vaccinated during the first week of life. Those 

 being kept for replacement were revaccinated at 18 weeks. Recently chicks 

 have been vaccinated at all ages to maturity. 



It is interesting to note that while a good take was observed in the 

 chicks vaccinated at an early age, the same birds revaccinated at 18 weeks 

 with combination Newcastle and Infectious Bronchitis vaccine by the spray 

 method showed little or no reaction. This conclusion was further borne out 

 by challenge and serological results, thus indicating that the resistance stim- 

 ulated by the spray technique for Newcastle and Infectious Bronchitis di- 

 seases may be present in chicks at 18 weeks of age. 



The resistance to Newcastle and Infectious Bronchitis stimulated by 

 such a procedure appeared to carry breeders through the season with no 

 breaks recorded on well over 1,000,000 birds. Further parental immunity 

 for both diseases was quite satisfactory in day-old chicks so vaccinated 

 hatched from breeders. 



During the past year, contrary to results of earlier experiments, it has 

 been found that parental immunity to Infectious Bronchitis does not have 

 as much bearing on early chick mass immunization as the Chronic Respira- 

 tory Disease Complex present in the chick at times of vaccination. Chronic 

 Respiratory Disease has also been found a complicating factor when birds 

 are vaccinated during the growing period. 



Vaccination by means of a dust preparation containing the combination 

 vaccine for Newcastle disease and Infectious Bronchitis has been tried on 

 some 20,000 birds. While serological tests and challenge results are en- 

 couraging, further trials will be necessary. Dust vaccination has had insuf- 

 ficient field trials, but it is another means of mass immunization which saves 

 considerable time and labor. 



In summarizing the work on this project, it has been demonstrated 

 that mass immunization by the spray technique is an effectual method of 

 controlling Newcastle disease and Infectious Bronchitis in replacement 

 flocks as well as in broilers, thereby emphasizing that mass immunization of 

 birds against Newcastle disease and Infectious Bronchitis is a reality today 

 in the poultry industry. 



W. R. DUNLOP 



Early Wing Web Vaccination for the 

 Prevention of Newcastle Disease 



In order to determine the feasibility of vaccinating chicks under 4 

 weeks of age for the prevention of Newcastle disease with wing web vac- 

 cine, trials have been conducted utilizing the vaccine at 7 and 14 days of 

 age. Parallel groups of parentally immune and parentally susceptible chicks 

 were used. Each treatment group was run in duplicate. 



In the trial when the chicks were vaccinated at 7 days of age, two 

 chicks out of 40 died from the susceptible groups and 5 others were visibly 

 abnormal. None of the parentally immune chicks were visibly affected. 

 Upon challenge with a virulent strain of Newcastle virus at 5 weeks, all 

 chicks remaining of the parentally susceptible groups survived except one 

 runt. In the case of the parentally immune groups, 1 1 died and 1 1 showed 

 symptoms upon the 5 week challenge. 



In the trial when the chicks were vaccinated at 14 days of age, the ex- 

 perimental design was the same as with the younger chicks. Upon challenge 



40 



