Pathogenicity, colonization, and innate immune response to Pasteurella multocida in rabbits

Area of Science:

• Veterinary Pathology
• Infectious Diseases
• Immunology

Background:

• Pasteurella multocida (P. multocida) is a significant rabbit pathogen causing economic losses.
• Understanding P. multocida pathogenesis and immune response is crucial for disease management.

Purpose of the Study:

• To elucidate the pathogenic mechanisms of P. multocida in rabbits.
• To investigate the innate immune response following P. multocida infection.

Main Methods:

• Rabbit infection model with P. multocida.
• Clinical observation, pathological, and histopathological analysis.
• Bacterial load quantification in tissues and analysis of Toll-like receptor (TLR) and cytokine expression.

Main Results:

• P. multocida infection caused severe dyspnea, high mortality (60%), and significant lung pathology (consolidation, abscesses).
• Rapid bacterial replication occurred in multiple tissues, peaking at 2 days post-infection (dpi), with sustained high levels in lungs and thymus at 3 dpi.
• TLR2 and TLR4 signaling pathways were activated, leading to increased expression of pro-inflammatory cytokines (Il1β, Il6, Il8, Tnf-α), correlating with bacterial colonization.

Conclusions:

• P. multocida rapidly replicates in rabbits, leading to bacteremia and significant respiratory inflammation.
• Activation of TLR signaling pathways and subsequent cytokine induction are key contributors to the observed respiratory inflammation and septicemia.