Examination of intra-sinus infraorbitalis chicken challenge model of Avibacterium paragallinarum serotype A for vaccine efficacy trials

Abstract

Infectious Coryza, caused by Avibacterium paragallinarum, is a significant poultry respiratory disease, particularly in the developing countries. It causes marked economic losses by growth retardation and drop in egg production. Vaccination is the most effective preventive measure against IC. The ability of the vaccine to prevent infection is tested in laboratory challenge conditions where the challenge strain, its dose and the challenge route play a crucial role. This study summarizes the establishment of an intra-sinus challenge model of a serotype A strain for vaccine efficacy testing and its testing in a vaccination-challenge efficacy design. In contrast to the literature statements, our results supported the usefulness of the direct intra-sinus challenge method using a high titre of challenge bacteria, which is estimated with high accuracy on the day of challenge using the OD measurement of the culture. This method was successfully applied in an efficacy test with a commercially available combined IC vaccine.