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TRICHINELLOSIS

Evolution
Larvae
Cysts
Inflammation
Muscle fibers
  Infection
  Myopathy
Chronic


Trichinellosis: Active


Trichinella Myopathy: Evolution


Trichinellosis: Active Myopathy


Myopathy: Multifocal, Ongoing

H&E stain
Muscle fibers: Necrosis & Replacement by large histiocytic cells

H&E stain

Gomori trichrome stain
Muscle fibers
  Ongoing myopathy: Necrosis & Replacement by large histiocytic cells
  Chronic changes: Internal nuclei in some muscle fibers

VvG stain

Muscle Fiber Damage: Evolution


Muscle Fiber Necrosis
  Pale muscle fiber cytoplasm (Arrow)

H&E stain

Muscle Fiber Necrosis: Cell invasion
  Cells in muscle fiber cytoplasm

H&E stain

Muscle Fiber Necrosis: Cell replacement
  Cells (Large, Histiocytic) replace muscle fiber

H&E stain

Trichinellosis: Muscle Fiber Invasion



VvG stain

VvG stain
Δ (Delta) lesions (White arrow)
  Focal, Subsarcolemmal (Early) changes in muscle fibers after larval invasion

H&E stain

NADH stain

Inclusions: Possible trichina larva within muscle fibers

VvG stain

VvG stain


VvG stain

NADH stain

Muscle fibers: Other pathology

VvG stain

VvG stain

VvG stain

VvG stain

Trichinellosis: Larvae

Extracellular, in endomysium, indenting muscle fibers

H&E stain

PAS stain

Trichinellosis: Unencysted extracellular larvae


H&E stain

H&E stain
  • Unencysted larva (White arrows)
  • Inflammatory foci: Surround extracellular, unencysted larva
    • Many cells in the infiltrates are histiocytes (macrophages) that
      • Contain nuclei that are larger and paler than those in T-cells
      • Stain with acid phosphatase and esterase (Below)
    • May include multinucleated giant cells (Above, Right; Below)

Acid phosphatase stain

Esterase stain

Multinucleated Giant Cell containing a Larva

H&E stain

Larva, extracellular: Surrounded by cells

VvG stain

Trichinellosis: Cysts

Contain larvae & Nurse cells


Congo red stain

Gomori trichrome stain
  • Larvae: Encased in cysts within muscle
  • Each cyst contains one coiled larva (Strongly stained by PAS (Below))
  • Cysts also contain "nurse" cells with large nuclei
  • The outer edge of the cyst is a well-defined wall
  • "Fluid" in cysts stains with NADH & Alkaline phosphatase(Below)
  • There is little inflammation around well-formed cysts

PAS stain

Acid phosphatase stain

VvG stain

NADH stain


ATPase pH 4.3 stain


Alkaline phosphatase stain
Contents of cyst around larvae & Vessels around cyst stain with alkaline phosphatase

Eosinophils

Present in vessel but not in extravascular regions

H&E stain

Trichinellosis: Chronic

Cysts without larvae


Cyst
  Inflammatory cells
  No larvae

H&E stain


H&E stain
Cysts: Empty
  Surrounding muscle: No inflammation or active myopathic changes

H&E stain

Calcification inside cyst

H&E stain


Trichinella spiralis: Lifecycle


CDC
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11/26/2016