The U.S. Poultry & Egg Association and the USPOULTRY Foundation have completed a funded research project at the University of Georgia and the U.S. Department of Agriculture Southeast Poultry Research Laboratory regarding the finding of a genetic code for creating safer vaccines for infectious laryngotracheitis. The project is part of the association’s comprehensive research program encompassing all phases of poultry and egg production and processing.


The live vaccines that are used to control infectious laryngotracheitis in chickens have the potential to regain their virulence when they spread from chicken to chicken in the field. This characteristic of the vaccines has limited their use in some instances and induced vaccine-related disease in some cases. The genetic basis for how these vaccines regain their virulence has been poorly understood. 

Dr. Maricarmen Garcia, University of Georgia, and Dr. Stephen Spatz, USDA Southeast Poultry Research Laboratory, successfully determined the full genome sequences for the two most common live ILT vaccines. They then allowed the vaccines to spread in chickens and looked at the DNA changes in the genomes of the vaccine viruses after they had been allowed to spread one time and again after they had been allowed to spread twenty times. Through this process, they determined which genetic sequences are responsible for the virulence of the virus. This new genetic information will allow researchers to create vaccines which do not have these genetic virulence markers, providing the basis for future effective, safe vaccines to protect the chicken industry against infectious laryngotracheitis.