Host responses associated with chronic staphylococcal mastitis in rabbits

Area of Science:

• Veterinary Immunology
• Bacterial Pathogenesis
• Animal Science

Background:

• Staphylococcal infections, particularly Staphylococcus aureus mastitis, cause significant economic losses in commercial rabbit farming.
• Chronic mastitis primarily affects breeding female rabbits, with ST121 and ST96 lineages of S. aureus being common causative agents.

Purpose of the Study:

• To characterize the host immune response in naturally occurring rabbit mastitis caused by S. aureus.
• To evaluate the relationship between peripheral and local immunity in affected rabbits.
• To investigate how different S. aureus genotypes (ST121 vs. ST96) influence these immune responses.

Main Methods:

• Histological and immunohistochemical analysis of mammary gland tissues from 204 affected rabbits.
• Flow cytometric analysis of peripheral blood immune cells.
• Multilocus sequence typing (MLST) to identify S. aureus genotypes (ST121 and ST96).

Main Results:

• Immune cell infiltration varied with lesion maturity; immature lesions showed higher cellularity with more T lymphocytes, macrophages, and plasma cells.
• A positive correlation was observed between peripheral monocytes and mammary tissue macrophages.
• Infection with ST96 strains was associated with significantly fewer granulocytes and higher numbers of B cells, T cells, CD4(+) T cells, and CD8(+) T cells compared to ST121 strains.

Conclusions:

• Rabbit mammary gland immune responses to S. aureus infection are genotype-dependent.
• ST96 strains induce a more robust adaptive immune response (T and B cells) than ST121 strains.
• Understanding these genotype-specific immune profiles can inform strategies for managing staphylococcal mastitis in rabbits.