JPC SYSTEMIC PATHOLOGY
MUSCULOSKELETAL SYSTEM
March 2019
M-B01

Signalment (ACVP# 75-28):  5-month-old Hereford calf    

HISTORY:  This animal was from a feedlot containing 42 cattle.  Over a period of 2 weeks, 4 calves died.  The gross lesions consisted of hemorrhagic edematous foci in the muscles with gaseous crepitation of the adjacent tissues.

HISTOPATHOLOGIC DESCRIPTION:  Skeletal muscle:  Affecting greater than 80% of the skeletal muscle there is marked expansion of fascial planes (epimysium, perimysium, and endomysium) up to 300um, with separation of muscle fascicles and individual myocytes by moderate to abundant amounts of fibrin, hemorrhage, and edema, admixed with degenerate neutrophils and karyorrhectic and cellular debris (necrosis).  There is extensive monophasic myofiber acute necrosis characterized by hypereosinophilic, fragmented sarcoplasm and myofibrils, loss of cross striations, pyknosis, and karyolysis.  Multifocally, there are fewer areas of myofiber degeneration characterized by myofiber swelling and vacuolation.  Multifocally there are ectatic lymphatics, and variably sized, up to 2mm diameter, well demarcated clear spaces that compress adjacent myocytes (emphysema).  Within adjacent adipose tissue, there is expansion by a neutrophilic serohemorrhagic infiltrate admixed with abundant 2-4um basophilic bacilli and beaded eosinophilic material (fibrin).

Lymph node:  Expanding the subcapsular sinus, filling trabeculae, and obscuring follicular architecture, are numerous erythrocytes and fewer neutrophils.

MORPHOLOGIC DIAGNOSES:  

  1. 1. Skeletal muscle:  Myositis, necrohemorrhagic, acute, diffuse, severe, with emphysema, edema, and numerous 2-4um intralesional bacilli, Hereford, bovine.
  2. Lymph node: Draining hemorrhage, acute, diffuse, severe.

ETIOLOGIC DIAGNOSIS:  Clostridial myositis

CAUSE:  Clostridium chauvoei

CONDITION:  Blackleg

SYNONYMS:  Black-quarter, emphysematous gangrene

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

Myopathy:

Sudden death in cattle:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Abreu CC, Blanchard PC, Adaska JM, et al. Pathology of blackleg in cattle in California, 1991-2015. J Vet Diag Invest. 2018;30(6):894-901.
  2. Abreu CC, Edwards EE, Edwards JF, et al. Blackleg in cattle: A case report of fetal infection and a literature review. J Vet Diag Invest. 2017;29(5):612-621.
  3. Constable PD, Hinchcliff KW, Done SH, Grunberg W. Veterinary Medicine. 11th ed. St Louis, MO: Elsevier Ltd; 2017:1430-1432.
  4. Cooper BJ, Valentine BA. Muscle and Tendon. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. St. Louis, MO: Elsevier; 2016:230-34.
  5. Valentine BA. Skeletal muscle. In: McGavin MD, Zachary JF, eds. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier Inc; 2017:926, 933, 940-941.


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