JPC SYSTEMIC PATHOLOGY
MUSCULOSKELETAL SYSTEM
April 2019
M-T02 

Signalment (ACVP/75-25):  2-year-old red Angus cow

HISTORY:  This is one of 14 surviving cows from a small herd in Southeast Texas.  Sixteen cows died suddenly or after being down for less than 24 hours.  The cows had grazed a coastal Bermuda grass pasture that contained toxic weeds.  The cow was alert and had a good appetite but would not rise from sternal recumbency.

HISTOPATHOLOGIC DESCRIPTION:  Skeletal muscle:  Approximately 50% of myocytes are swollen up to 100 um in diameter with pale, often vacuolated sarcoplasm,  indistinct cross-striations and disrupted myofibrils (degeneration), or shrunken and angulated profiles with homogeneous hypereosinophilic hyalinzed sarcoplasm, disorganized fragmented myofibrils, loss of cross-striations, prominent contraction bands and pyknotic nuclei (necrosis).  Multifocal aggregates of hyperplastic and hypertrophied satellite cells surround affected myocytes, which occasionally contain intrasarcoplasmic macrophages and satellite cells.  Rarely, myocytes have basophilic sarcoplasm with internalized, “rowed” vesiculate nuclei (regeneration).  Surrounding affected myofibers are few scattered macrophages and rare neutrophils. 

MORPHOLOGIC DIAGNOSIS:  Skeletal muscle, myocytes:  Degeneration and necrosis, acute, multifocal, moderate, with rare regeneration, red Angus cow, bovine.

ETIOLOGIC DIAGNOSIS:  Phytotoxic myopathy

CAUSE:  Senna sp. (formerly Cassia sp.)

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ULTRASTRUCTURAL FINDINGS:

DIFFERENTIAL DIAGNOSIS:  Other toxic myopathies and cardiomyopathies: 

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Cooper BJ, Valentine BA. Muscle and Tendon. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. St Louis, MO: Elsevier; 2016: 219-220.
  2. Haraguchi M, Calore EE, Dagli MLZ, et al. Muscle atrophy induced in broiler chicks by parts of Senna occidentalis Vet Res Comm. 1998;22:265-271.
  3. Jones TC, Hunt RD, King NW. Diseases due to extraneous poisons. In: Veterinary Pathology. 5th ed. Baltimore, MD: Williams and Wilkins; 1997:770-771.
  4. Rissi DR, L Barros CS. Pathology in Practice. J Am Vet Med Assoc. 2017;250(1):51-53.
  5. Sebastian MM. Role of pathology in diagnosis. In: Gupta RC, ed. Veterinary Toxicology: Basic and Clinical Principles. Ney York, NY: Elsevier; 2007:1120.
  6. Valentine BA, Skeletal Muscle. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:925.


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