Inflammatory Myopathy in Horses With Chronic Piroplasmosis.
Authors: Pasolini Maria P, Pagano Teresa B, Costagliola Alessandro, Biase Davide De, Lamagna Barbara, Auletta Luigi, Fatone Gerardo, Greco Michele, Coluccia Pierpaolo, Vincenzo Veneziano, Pirozzi Claudio, Raso Giuseppina Mattace, Santoro Pasquale, Manna Giuseppe, Papparella Serenella, Paciello Orlando
Journal: Veterinary pathology
Summary
Chronic equine piroplasmosis commonly manifests as performance decline and muscle wasting, yet the underlying mechanisms driving myopathy remain poorly characterised. Researchers examined muscle biopsies from 16 serologically positive horses displaying clinical and biochemical evidence of myopathy, analysing tissue architecture, immune cell populations, circulating autoantibodies, and inflammatory cytokine expression using histopathology, immunohistochemistry, immunofluorescence, and molecular techniques. Muscle atrophy was universal, whilst 81% showed degenerative changes and lymphocytic infiltration; notably, 94% of muscle fibres displayed strong MHC class I and II staining, and circulating autoantibodies against sarcolemmal antigens were detected in all affected horses, with significantly elevated interferon-γ, interleukin-12, and TNF-α gene expression compared to healthy controls—critically, piroplasm organisms were not detected within muscle tissue itself. These findings suggest that chronic piroplasmosis triggers an autoimmune-mediated inflammatory cascade rather than direct parasitic invasion of muscle, explaining the progressive atrophy and performance issues observed clinically. For practitioners managing chronically infected horses, this autoimmune mechanism implies that standard antiprotozoal treatment alone may be insufficient; consideration of anti-inflammatory interventions and immune modulation alongside parasite clearance could warrant investigation to prevent irreversible myopathic damage.
Read the full abstract on PubMed
Practical Takeaways
- •Horses with chronic piroplasmosis presenting with poor performance and muscle atrophy may have autoimmune-mediated myopathy; consider serology and muscle biopsy for diagnosis
- •Autoimmune mechanisms appear central to piroplasmosis-associated myopathy, suggesting immune-modulating treatments may warrant investigation alongside anti-parasitic therapy
- •Muscle fiber atrophy and degeneration in chronically infected horses likely results from inflammatory cytokine activity rather than direct parasite damage to muscle tissue
Key Findings
- •All 16 affected horses showed muscle fiber atrophy with 81% presenting degenerative changes and lymphocytic infiltration
- •94% of cases demonstrated strong MHC class I and II immunostaining on muscle fibers, indicating autoimmune-mediated muscle damage
- •Circulating autoantibodies against muscle antigens were detected in serum from all affected horses via sarcolemmal staining
- •Significantly elevated interferon-γ, interleukin-12, and TNF-α gene expression in affected muscle tissue compared to healthy controls