JPC SYSTEMIC PATHOLOGY
Musculoskeletal System
April 2019
M-P02

Signalment (ACVP 75-34):  1-year-old pig 

HISTORY:  Clinical signs consisted of lameness, especially of the hind legs, anorexia, weight loss, malaise and rough hair coat.

HISTOPATHOLOGIC DESCRIPTION:  Skeletal muscle:  Multifocally replacing myocytes are numerous granulomas composed of a central area of necrotic, often mineralized cellular debris and degenerate nematode larvae surrounded by moderate numbers of epithelioid macrophages, foreign body and Langhans type multinucleated giant macrophages, further surrounded by fewer eosinophils, lymphocytes, plasma cells and concentric rings of reactive fibroblasts and fibrous connective tissue.   Multifocally hypertrophied myocytes with abundant eosinophilic fibrillar cytoplasm and multiple large, disorganized, vesiculate nuclei (nurse cells) contain intrasarcoplasmic 75-150 um diameter cysts with a 10 um thick, eosinophilic, hyalinzed wall that contains cross sections of nematode larvae.  Larvae are 25-30 um in diameter with a thin, eosinophilic cuticle, coelomyarian and polymyarian musculature, bilateral hypodermal bands, a cluster of basophilic cells that surround an esophagus (stichosome), musculature, intestinal tract and developing gonad.  Occasionally, encysted larvae are surrounded by moderate numbers of previously described inflammatory cells; other involved myocytes contain only debris from remnants of nematode larvae and mineral. Occasionally, adjacent myofibers are shrunken and brightly eosinophilic (atrophy) or are replaced by fibrous connective tissue. 

MORPHOLOGIC DIAGNOSIS:  Skeletal muscle:  Granulomas, eosinophilic, multifocal, moderate, with hypertrophied myocytes (nurse cells) with intra-sarcoplasmic, encysted aphasmid larvae, pig, porcine.

ETIOLOGIC DIAGNOSIS:  Trichinella myositis

CAUSE:  Trichinella spiralis

CONDITION:  Trichinosis, Trichinellosis 

GENERAL DISCUSSION:

LIFE CYCLE:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS: 

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS: 

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 1. 6th ed. St. Louis: Elsevier; 2016:237-238.
  2. Dmitric M, Vidanovic D, Vaskovic N, et al. TRICHINELLA INFECTIONS IN RED FOXES (VULPES VULPES) AND GOLDEN JACKALS (CANIS AUREUS) IN SIX DISTRICTS OF SERBIA. J Zoo Wildl Med. 2017 Sep;48(3):703-707.
  3. Gardiner CH, Poynton SL. An Atlas of Metazoan Parasites in Animal Tissues. Washington, DC: Armed Forces Institute of Pathology; 2009:3, 13, 40-42.
  4. Larter NC, Elkin BT, Forbes LB, Wagner B, Allaire Trichinella Surveillance in Black Bears ( Ursus americanus) from the Dehcho Region, Northwest Territories, Canada, 2002–15. J Wildl Dis. 2017;53(2):405-407.
  5. McAdam AJ, Milner DA, Sharpe AH. Infectious diseases. In: Kumar V, Abbas AK, Aster JC, eds. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Philadelphia, PA: Saunders Elsevier; 2015:396-397.
  6. Oltean M, Kalmar Z, Kiss BJ, et al. European mustelids occupying pristine wetlands in the Danube Delta are infected with Trichinella likely derived from domesticated swine. J Wildl Dis. 2014;50(4):972-975.
  7. Robinson WF, Robinson NA. Cardiovascular system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. St. Louis: Elsevier; 2016:44.
  8. Valentine BA. Skeletal muscle. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:927, 945.


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