Comparative Analysis Of Pathogenesis In Two Strains Of Infectious Bronchitis Virus In Chicks: Implications For Future Research

Abstract

Infectious bronchitis virus (IBV) is a highly contagious respiratory pathogen in chickens, causing severe illness, particularly in young chicks. This study compares the early pathogenicity of two IBV strains, Massachusetts M41 and Moroccan G, in specific pathogen-free (SPF) chicks infected at one day old. The aim was to investigate the kidney’s role in viral persistence and determine the most suitable strain for further experimental studies.
Post-infection, serum IgG and IgM levels peaked on the same day for both strains, despite a delayed infection with strain G. However, the IgG response to M41 was higher over the same period, possibly due to a delayed uptake of strain G. Previous studies relied solely on virus isolation to assess persistence, whereas this study incorporated RT-PCR to improve detection sensitivity.
Unexpectedly, M41 produced clinical signs at the expected time post-inoculation, whereas strain G induced disease only at 10 days post-infection. The reason for this delay remains unclear. Strict biosecurity measures ensured separate housing, minimizing cross-contamination. Virus G was isolated from the lung and rectum as early as day 3, confirming successful infection. Although the IgG profile suggested a delayed infection, IgM results provided no further clarity.
This study highlights key differences in the early pathogenicity of M41 and strain G, emphasizing the need for further research on viral persistence and immune response dynamics in chickens.