Poster Presentation 12th Australasian Virology Society Meeting 2024

Emergence and Molecular Characterisation of a Novel Variant of Infectious Bronchitis Virus in Poultry from Victoria, Australia (#201)

Karim Mardani 1 , Amir H. Noormohammadi 1 , Andrés Diaz-Méndez 1 , Songhua Shan 1 , Sunita Sumanam 2 , Neil D. Young 2 , Arif Anwar 3 , Glenn F. Browning 1
  1. Asia-Pacific Centre for Animal Health, Melbourne Veterinary School, Faculty of Science, The University of Melbourne, Parkville, Vic 3010, Australia
  2. Department of Veterinary Biosciences, Melbourne Veterinary School, Faculty of Science, The University of Melbourne, Parkville, Vic 3010, Australia
  3. Scolexia Pty Ltd, Moonee Ponds, 3039, Victoria, Australia

Infectious bronchitis virus (IBV) poses a significant economic threat to poultry production globally. The continuous evolution of IBV has led to the emergence of numerous antigenically and genetically distinct variants, making disease prevention and control increasingly challenging. In August 2023, caecal tonsil tissues from two different free-range poultry farms (layers) with a history of IBV vaccination of chickens, where chickens exhibited false layer syndrome without any clinical signs, were submitted to Asia-Pacific Centre for Animal Health diagnostic Laboratory, Melbourne Veterinary School, University of Melbourne. Initial IBV PCR-HRM identified IBV variant strains from one farm and indistinguishable strain from the subgroup 1 IBV reference strains (vaccine strain) from the other farm. The viruses were propagated in embryonated SPF eggs, and their genomes were sequenced using Nanopore technology. The two isolates were molecularly characterised and designated as Chicken/AU/V806-2/23 and Chicken/AU/V817-3B/23. Comparative full-length sequence analysis revealed that Chicken/AU/V806-2/23 was a distinct recombinant virus, likely resulting from genetic recombination between the structural and non-structural genes of the VicS and Armidale (A3) vaccine strains. Chicken/AU/V817-3B/23 was found to be 99.94% identical to the VicS vaccine strain of IBV. False layer syndrome has previously been associated with specific IBV strains, such as DMV1639, QX, Massachusetts, and the Australian T strains. The new recombinant IBV may be linked to the false layer syndrome observed on the affected farms. To establish effective vaccination and control programs, it is crucial to enhance biosecurity and surveillance measures. Future studies should also focus on characterising newly emerging IBV strains, specifically investigating their virulence, tissue tropism, and pathogenesis.