Difference between revisions of "Hepatozoon"

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***Grossly:
 
***Grossly:
 
****Thickened and edematous periskeletal soft tissue and periosteum of the lower legs
 
****Thickened and edematous periskeletal soft tissue and periosteum of the lower legs
****Multifocal [[Muscles Inflammatory - Pathology#Parasitic myositis|parasitic myositis]]
+
****Multifocal [[Parasitic Myositis|parasitic myositis]]
 
***Histologically:
 
***Histologically:
 
****Swelling and hypertrophy of osteoprogenitor cells  
 
****Swelling and hypertrophy of osteoprogenitor cells  
 
****Hyperplasia of spindle cells
 
****Hyperplasia of spindle cells
 
****Osteoid is produced
 
****Osteoid is produced
*[[More Hepatozoon|More detail on ''Hepatozoon americanum'']]
+
 
 
*Myositis
 
*Myositis
 
**Develop cysts in skeletal muscle of dogs and cats
 
**Develop cysts in skeletal muscle of dogs and cats
 
**May be accompanied by pyogranulomatous myositis - macrophages and [[Neutrophils|neutrophils]] mainly with occasional other cells
 
**May be accompanied by pyogranulomatous myositis - macrophages and [[Neutrophils|neutrophils]] mainly with occasional other cells
[[Category:Protozoa]][[Category:To_Do_-_Parasites]]
+
 
 +
 
 +
'''[Skeletal lesions of canine hepatozoonosis caused by Hepatozoon americanum. Panciera Rj et al. Vet Path (2000) 37 225-230]'''
 +
 
 +
*[[Coccidia|'''''Hepatozoon americanum''''']]
 +
**SE USA
 +
**Clinical signs:
 +
***Fever
 +
***Weakness
 +
***Myalgia
 +
***Bone pain
 +
***Mature neutrophilic leukocytosis
 +
***Wasting
 +
***Poor response to treatment
 +
***Periosteal new bone formation
 +
**Much more aggressive and higher mortality rate than the disease in the Old World
 +
**Gross skeletal lesions:
 +
***Markedly thickened and edematous periskeletal soft tissue and periosteum of the lower legs ***+/- petechiation
 +
***Eccentrically or circumferentially arranged plaques of new bone formation deposited on the original cortex
 +
***Boney plaques look ‘porous’ to compact, often in layers with the spongey areas covered by more compact bone
 +
***No evidence of endosteal bone formation
 +
***Periosteoproliferative lesions most prominent in proximal long bones of the limbs (esp. femur and humerus)
 +
***Metaphyses usually spared
 +
***Caudal and lateral surfaces of the proximal tibia and fibular and radius and ulnar diaphyses affected
 +
***Distal diaphyses and metaphyses less severely affected/free from lesions
 +
***Metacarpals/tarsals mildly affected
 +
***Lateral surface of scapula affected
 +
***Axial skeleton less severely affected
 +
***Often bones of the skull prominently affected – orbits, rostrolateral maxilla and mandible, lateral aspect of zygomatic arch
 +
***Lateral aspects of vertebral arches and spinous processes sometimes affected
 +
***Ribs normal
 +
***Multifocal [[Parasitic Myositis|parasitic myositis]]
 +
**Histologically:
 +
***Earliest change in periosteum -> swelling and hypertrophy of osteoprogenitor cells in the deeper layers of the periosteum
 +
***Spindle cells become stellate and plumper
 +
****Become aligned in single or multiple layers
 +
****Undergo hyperplasia creating a thick and densely cellular zone on the cortical surface
 +
***Osteoid is produced and osteoblasts become entrapped forming spiccules of trabecular new bone
 +
***New spicules arranged perpendicular to the cortical surface
 +
***With time, considerable osteoclastic activity, remodeling occurs firstly adjacent to the older cortex and then extends outwards
 +
***As the remodeling continues, the spicules become longitudinally arranged
 +
***Pseudocortices form that can contain bone marrow parenchyma
 +
***Endothelial hypertrophy prominent in vessels adjacent and within the periosteum
 +
***Severe edema present in adjacent soft tissue
 +
***Muscle atrophy and fibrosis often accompanied the edema
 +
***No evidence of inflammation
 +
***No parasites in adjacent muscle/soft tissue
 +
**Lesions develop in young dogs, within 5wks of experimental infection and progress rapidly, looking just like hypertrophic osteopathy
 +
**No obvious link between site of infection and generalized boney lesions
 +
*Differentials for periosteal new bone formation:
 +
**[[Hypertrophic Osteopathy|Hypertrophic osteopathy]]
 +
**[[Craniomandibular Osteopathy|Craniomandibular osteopathy]]
 +
**[[Panosteitis|Canine panosteitis]]
 +
**[[Hypertrophic Osteodystrophy|Hypertrophic osteodystrophy]]
 +
*Hypertrophic osteoarthropathy
 +
**V difficult to distinguish from this syndrome
 +
**Again no inflammation, histologically look identical, but these cases don’t have an abdominal/thoracic mass, and HO usually starts on the metacarpals/tarsals
 +
*?Pathogenesis
 +
**Thought to occur secondary to increased blood flow and fluid retention within the limbs, leading to vascular and then periosteal proliferation
 +
 
 +
 
 +
[[Category:Miscellaneous Protozoa]][[Category:To_Do_-_Parasites]]
 +
[[Category:Bones - Pathology]]

Latest revision as of 23:09, 5 March 2011

  • Tick borne disease
  • Two species:
    • Hepatozoon canis
      • Usually subclinical disease
    • Hepatozoon americanum
      • SE USA
      • Grossly:
        • Thickened and edematous periskeletal soft tissue and periosteum of the lower legs
        • Multifocal parasitic myositis
      • Histologically:
        • Swelling and hypertrophy of osteoprogenitor cells
        • Hyperplasia of spindle cells
        • Osteoid is produced
  • Myositis
    • Develop cysts in skeletal muscle of dogs and cats
    • May be accompanied by pyogranulomatous myositis - macrophages and neutrophils mainly with occasional other cells


[Skeletal lesions of canine hepatozoonosis caused by Hepatozoon americanum. Panciera Rj et al. Vet Path (2000) 37 225-230]

  • Hepatozoon americanum
    • SE USA
    • Clinical signs:
      • Fever
      • Weakness
      • Myalgia
      • Bone pain
      • Mature neutrophilic leukocytosis
      • Wasting
      • Poor response to treatment
      • Periosteal new bone formation
    • Much more aggressive and higher mortality rate than the disease in the Old World
    • Gross skeletal lesions:
      • Markedly thickened and edematous periskeletal soft tissue and periosteum of the lower legs ***+/- petechiation
      • Eccentrically or circumferentially arranged plaques of new bone formation deposited on the original cortex
      • Boney plaques look ‘porous’ to compact, often in layers with the spongey areas covered by more compact bone
      • No evidence of endosteal bone formation
      • Periosteoproliferative lesions most prominent in proximal long bones of the limbs (esp. femur and humerus)
      • Metaphyses usually spared
      • Caudal and lateral surfaces of the proximal tibia and fibular and radius and ulnar diaphyses affected
      • Distal diaphyses and metaphyses less severely affected/free from lesions
      • Metacarpals/tarsals mildly affected
      • Lateral surface of scapula affected
      • Axial skeleton less severely affected
      • Often bones of the skull prominently affected – orbits, rostrolateral maxilla and mandible, lateral aspect of zygomatic arch
      • Lateral aspects of vertebral arches and spinous processes sometimes affected
      • Ribs normal
      • Multifocal parasitic myositis
    • Histologically:
      • Earliest change in periosteum -> swelling and hypertrophy of osteoprogenitor cells in the deeper layers of the periosteum
      • Spindle cells become stellate and plumper
        • Become aligned in single or multiple layers
        • Undergo hyperplasia creating a thick and densely cellular zone on the cortical surface
      • Osteoid is produced and osteoblasts become entrapped forming spiccules of trabecular new bone
      • New spicules arranged perpendicular to the cortical surface
      • With time, considerable osteoclastic activity, remodeling occurs firstly adjacent to the older cortex and then extends outwards
      • As the remodeling continues, the spicules become longitudinally arranged
      • Pseudocortices form that can contain bone marrow parenchyma
      • Endothelial hypertrophy prominent in vessels adjacent and within the periosteum
      • Severe edema present in adjacent soft tissue
      • Muscle atrophy and fibrosis often accompanied the edema
      • No evidence of inflammation
      • No parasites in adjacent muscle/soft tissue
    • Lesions develop in young dogs, within 5wks of experimental infection and progress rapidly, looking just like hypertrophic osteopathy
    • No obvious link between site of infection and generalized boney lesions
  • Differentials for periosteal new bone formation:
  • Hypertrophic osteoarthropathy
    • V difficult to distinguish from this syndrome
    • Again no inflammation, histologically look identical, but these cases don’t have an abdominal/thoracic mass, and HO usually starts on the metacarpals/tarsals
  • ?Pathogenesis
    • Thought to occur secondary to increased blood flow and fluid retention within the limbs, leading to vascular and then periosteal proliferation