Comparison of the pathogenicity of QX-like, M41 and 793/B infectious bronchitis strains from different pathological...

Area of Science:

• Veterinary Virology
• Avian Pathology
• Immunology

Background:

• Infectious bronchitis virus (IBV) poses a significant threat to poultry health and economic stability.
• Understanding the pathogenicity and organ tropism of different IBV serotypes is crucial for effective disease control strategies.

Purpose of the Study:

• To compare the pathogenicity of five QX-like IBV strains and two reference strains (M41, 793/B) in specific pathogen-free chickens.
• To evaluate differences in ciliary activity inhibition, immune response, viral replication, and histopathological lesions.
• To determine organ distribution and identify characteristic lesions associated with different IBV serotypes.

Main Methods:

• Infection of 1-day-old specific pathogen-free chickens with five QX-like IBV strains and two reference strains.
• Monitoring of trachea epithelium ciliary activity, immune response (ELISA), viral replication, and histopathological lesions over 42 days post-infection.
• Repeated samplings for comprehensive analysis of pathogenicity and organ distribution.

Main Results:

• Significant differences in pathogenicity and organ distribution were observed among the three IBV serotypes.
• Strain 793/B exhibited limited organ invasion but induced a robust humoral immune response.
• QX-like strains generally replicated to higher titers, with the Chinese isolate causing the most severe lesions and highest antibody titers.
• Prominent lesions included severe kidney damage and oviduct dilatation, particularly associated with QX-like IBV strains.

Conclusions:

• QX-like IBV strains demonstrate distinct pathogenic profiles, including significant kidney damage and oviduct alterations.
• Variability exists within QX-like strains regarding pathogenicity and organ tropism.
• Understanding these differences is vital for developing targeted interventions against IBV.