JPC SYSTEMIC PATHOLOGY
MUSCULOSKELETAL SYSTEM
April 2019
M-V01 (NP)

Signalment (ACVP #75-31):  Age unspecified ewe

HISTORY:  This ewe was 1 of 30 animals that presented with fever, facial edema, purulent nasal exudate, profuse salivation, ulcers at the commissures of the mouth, and coronitis.  At necropsy there were ulcers along the edge of the lips but no lesions in the oral cavity.  The coronary bands were hyperemic with hemorrhagic areas.  Muscles of the extremities displayed longitudinal light tan and dark red streaking of muscle fibers.  Multifocally the subcutis contained gelatinous edema fluid.

HISTOPATHOLOGIC DESCRIPTION:  Skeletal muscle:  Diffusely, muscle fibers are either swollen with vacuolated sarcoplasm (degeneration) or fragmented, with eosinophilic to amphophilic hyalinized sarcoplasm, loss of cross striations, pyknosis, and karyorrhexis (necrosis) with occasional mineralization.  Multifocally, separating, surrounding, and replacing degenerate and necrotic myofibers are macrophages, few lymphocytes, plasma cells, and neutrophils, scattered hemorrhage and fibrin, and variable amounts of reactive fibroblasts and collagen (fibroplasia).   There is rare regeneration characterized by invasion of lightly basophilic myofibers by satellite cells, forming a row of centralized nuclei, and occasional mitotic figures (myoblasts).  Multifocally, few blood vessels are lined by hypertrophied endothelial cells or have a disrupted endothelium with vessel walls that are fragmented and replaced by scattered pyknotic or karyorrhectic debris, fibrin, and few infiltrating neutrophils (fibrinoid and necrotizing vasculitis).  Between extant muscle fibers, there is increased clear space and few ectatic lymphatics (edema).  Within one myocyte, there is a single, oval, 40 x 60 um cyst containing numerous, elongate, 3 x 10 um basophilic bradyzoites (Sarcocystis sp.).

MORPHOLOGIC DIAGNOSIS: 

  1. Skeletal muscle:  Degeneration and necrosis, multifocal, moderate, with regeneration, multifocal fibrinoid vasculitis, hemorrhage, histiocytic myositis, and fibrosis, breed not specified, ovine.
  2. Skeletal muscle, myocyte: Sarcocyst. 

ETIOLOGIC DIAGNOSIS:  Orbiviral myositis

CAUSE:  Bluetongue virus (BTV; ovine orbivirus)

CONDITION:  Bluetongue

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

Sheep:

Cattle and goats:

TYPICAL GROSS FINDINGS:

Sheep:

Cattle and goats (recent European BTV serotype 8 epizootic):

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

Muscle degeneration/necrosis:

Similar systemic lesions:

Sheep:

Cattle:

White-tailed deer and mule deer:

COMPARATIVE PATHOLOGY (Orbiviruses):

REFERENCES:

  1. Allen AJ, Stanton JB, Evermann JF, Fry LM, Ackerman MG, Barrington GM. Bluetongue disease and seroprevalence in South American camelids from the northwestern region of the United States. J Vet Diagn Invest. 2015; 27(2):226-30.
  2. Barrat-Boyes SM, MacLachlan NJ. Pathogenesis of bluetongue virus infection of cattle. J Am Vet Med Assoc. 1995:206(9):1322-1329.
  3. Cantile C, Youssef S. Nervous system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. St. Louis, MO: Elsevier; 2016: 281.
  4. Johnson DJ, Ostlund EN, Stallnecht, Goekjian VH, Jenkins-Moore M, Harris SC. First report of bluetongue virus serotype 1 isolated from a white-tailed deer in the United States. J Vet Diagn Invest. 2006;18:398-401.
  5. Kienzle C, Poulson RL, Ruder MG, et al. Virus isolation and molecular detection of bluetongue and epizootic hemorrhagic disease viruses from naturally infected white-tailed Deer (Odocoileus virginianus) on St. John, US Virgin Islands. J Wildl Dis. 2017;53(4):843-849.
  6. Noon TH, Wesche SL, Cagle D, Mead DG, Bicknell EJ, Bradley GA, Riplog-Peterson S, Edsall D, Reggiardo C. Hemorrhagic disease in bighorn sheep in Arizona. J Wildl Dis. 38:172-176, 2002.
  7. Reuter JD, Nelson SL. Hematologic parameters and viral status for Zika, Chikungunya, bluetongue, and epizootic hemorrhagic disease in white-tailed deer. J Wildl Dis. 2018;54(4):843-847.
  8. Ruder MG, Johnson D, Ostlund E, et al. The first 10 years (2006–15) of epizootic hemorrhagic disease virus serotype 6 in the USA. J Wildl Dis. 2017;53(4):843-849.
  9. Ruder MG, Stallknecht DE, Allison AB, et al. Host and potential vector susceptibility to an emerging orbivirus in the United States: epizootic hemorrhagic disease virus serotype 6. J Wildl Dis. 2017;53(4):901-905.
  10. Schwartz-Cornil I, Mertens PPC, Contreras V, Hemati B, Pascale F, Breard E, Mellor PS, MachLachlan NJ, Zientata S. Bluetongue virus: virology, pathogenesis and immunity. Vet Res. 2008;39:46.
  11. Uzal FA, Platter BL, Hostetter JM. Alimentary System. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St Louis, MO: Elsevier; 2016:136-139, 145-146.
  12. Zachary JF. mechanisms of microbial infections. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:214.


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