Soo4ten^" SPRAY 



INCREASES IMMUNITY AGAINST NEWCASTLE 



By STEPHEN B. HITCHNER and GILBERT REISING, JR. 



IN ITS INCESSANT struggle to 

 conquer the forces of respiratory 



infection, Veterinary Science con- 

 tinues to pound at the still im- 

 pregnable line of Newcastle disease 

 — an ever-present threat to the 

 poultry industry. This respiratory 

 and nervous infection of poultry is 

 caused by a virus that may produce 

 a high mortality in young chickens 

 and a complete cessation of egg 

 production in laying flocks. It has 

 become so firmly established in the 

 United States that the develop- 

 ment of a method of immunization 

 to keep the disease under control is 

 urgently needed. 



Vaccines now available are the 

 killed virus, and two live-virus vac- 

 cines (the intranasal and wing-web) . 

 Each type has its advantages and 

 disadvantages, and to date no one 

 vaccine gives complete control of 

 the disease. That differences of 

 opinion do exist regarding the type 

 of vaccine to be used is an indication 

 that knowledge of the respective 

 merits of the vaccines is lacking 

 and that additional improvements 

 are needed in vaccines or vaccina- 

 tion procedures. 



Bi Strain Safe for Chicks 



Vaccination studies at this Sta- 

 tion have been devoted primarily 

 to the strain of virus used in the 

 intranasal vaccine, frequently re- 



*S. B. Hitchner, Research Professor, assisted by 

 G. Reising, Jr., Research Instructor, Veterinary 

 Science. 



f erred to as the Bi strain. Since 

 this strain causes such a mild reac- 

 tion, it can be used with safety in 

 chicks of any age without producing 

 any nervous symptoms. The im- 

 munity induced in day-old chicks 

 is not 100 percent effective, but 

 does provide most broiler flocks 

 with approximately 80 to 85 percent 

 protection up to market age, 



Recent tests have demonstrated 

 that to get protection each chick 

 must receive an adequate dose of 

 live-virus particles. Because of the 

 mild nature of this strain of virus, 

 the virus must reach the susceptible 

 tissues to be effective. Poultrymen 

 should not rely on contact exposure 

 to take care of the birds that are 

 poorly vaccinated. Therefore, to 

 get the greatest protection from the 

 intranasal vaccine, a vaccine con- 

 taining sufficient live-virus particles 

 must be administered to each chick, 

 with care, without stretching the 

 dosage. 



It has been recognized that dur- 

 ing the past season a few flocks have 

 experienced severe outbreaks of 

 Newcastle a few weeks after vac- 

 cination. The exact cause of lack 

 of protection in these cases is not 

 known but may be explained, in 

 part, by failure to observe the pre- 

 cautions previously mentioned. Re- 

 gardless of the cause, during certain 

 seasons of extreme exposure to 

 Newcastle, a higher degree of im- 

 munity may be needed to give 



