Toxic Myopathy
- Plants
- E.g. Cassia occidentalis (coffee senna), Karwinskia humboldtiana (coyotillo), Eupatorium rugosum (white snakeroot), cotton seed
- Lesion an skeletal and cardiac muscle
- Grossly:
- Pale areas with ill-defined borders
- May involve very extensive necrosis
- Histologically:
- Segmental necrosis, no calcification
- Regeneration may occur in surviving animals
- Drugs
- E.g. corticosteroids, cholinesterase inhibitors, vincristine, dimethyl sulfoxide (DMSO)
- Monensin is a coccidiostat toxic to horses, donkeys, zebras, cattle, sheep, dogs and birds
- Causes muscle necrosis in heart and skeletal muscle
- Grossly:
- Pale streaks, mostly in hind limbs
- Histologically:
- Segmental necrosis
- Possibly regeneration in surviving animals
- Can cause rapid onset recumbency and potentially death
- Usually due to mixing errors in feed
- Also from intramuscular injections, e.g. oxytetracycline, lidocaine, chloramphenicol, produce local necrosis
- As satellite cells are destroyes, repair is via fibrosis with some budding
- Chemicals
- Iron injections can cause local myonecrosis
- Mycotoxins
- Metabolites cause persistent tremors
- Lesions in skeletal muscle only, possibly secondary to sustained contractions (similar to exertional myopathy)
- Histologically:
- Tiny foci of segmental necrosis