Abstract Description

Infectious coryza (IC) in poultry remains a serious problem in many parts of the world despite the widespread use of various vaccines. Avibacterium paragallinarum is the bacterium responsible for IC infections in poultry and was first isolated in the 1930s. Early signs of infection in chickens can be seen in facial swelling, nasal discharge and sneezing. Untreated infection can lead to retardation in the growth experienced by broilers and a decrease in egg production. This can affect the food security of many countries that rely on poultry production as a main protein source. A. paragallinarum is divided into three (A, B and C) serogroups, with nine reference serovars. Identifying the serovars is crucial, as vaccines provide no cross-protection, particularly within serogroup C. A. paragallinarum requires a colony feeder that consistently supplies nicotinamide adenine dinucleotide (NAD + ), which contributes to the variant ability. A NAD + -independent strain of A. paragallinarum was isolated from the infected chickens. Previous studies indicated that this NAD + -independence was caused by a transmissible plasmid enabling the strains to grow without NAD + , making these strains less variant. Therefore, this plasmid was sequenced and transformed into the four main reference serovars of A. paragallinarum by creating competent cells and applying heat shock. Past studies have indicated that NAD + -independent strains are less variant when compared to NAD + -dependent strains. Therefore, this study investigates the potential of using the transformed reference serovars as an attenuated vaccine. The transformed serovars could enhance vaccination programs by serving as a live vaccine, which is what will be tested next with the transformed reference serovars.