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| − | {{review}}
| + | #redirect[[:Category:Muscles - Inflammatory Pathology]] |
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| − | {{toplink
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| − | |backcolour =CDE472
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| − | |linkpage =Musculoskeletal System - Pathology
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| − | |linktext =Musculoskeletal System
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| − | |maplink = Musculoskeletal System (Content Map) - Pathology
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| − | |pagetype =Pathology
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| − | |sublink1=Muscles - Pathology
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| − | |subtext1=MUSCLES
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| − | }}
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| − | <br>
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| − | ==Myositis==
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| − | | |
| − | *Inflammation of muscle
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| − | | |
| − | | |
| − | ===Bacterial myositis===
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| − | | |
| − | *Bacteria gain entry via:
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| − | **Direct penetration
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| − | **Blood stream
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| − | **Extension
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| − | *Lesions caused:
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| − | **Suppurative
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| − | **Serosanguinous
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| − | **Granulomatous
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| − | | |
| − | | |
| − | ====Abscesses====
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| − | | |
| − | *Caused by pyogenic bacteria
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| − | *Usually:
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| − | **[[Arcanobacter pyogenes|''Arcanobacterium pyogenes'']] in sheep and cattle
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| − | **[[Respiratory Bacterial Infections - Pathology#Strangles|''Streptococcus equi'']] in horses
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| − | **[[Corynebacterium species|''Corynebacterium pseudotuberculosis'']] in sheep and goats
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| − | **[[Pasteurella species and Mannheimia haemolytica|''Pasteurella multocida'']] causes cellulitis in cats
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| − | *Usually localised suppuration and necrosis of myofibres
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| − | *Occasionally my spread via the fascia
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| − | | |
| − | | |
| − | ====Black leg====
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| − | [[Image:Black leg myositis.jpg|right|thumb|100px|<small><center>Blackleg myositis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | | |
| − | *Causative agent: [[Clostridium species|''Clostridium chauvoei'']]
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| − | *May affect the fattest cattle at pasture in the summer
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| − | *Rapid toxaemia -> death
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| − | *If clinical signs observed:
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| − | **Toxaemia -> pyrexia, depression, [[Lungs Circulatory - Pathology#Pulmonary oedema|pulmonary oedema]], circulatory collapse
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| − | **Muscle lesions -> lameness, swollen hot muscles later becoming cool as necrosis sets in
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| − | *Pathogenesis:
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| − | **Spores gain entry to GI tract -> blood -> muscle -> lie latent
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| − | **Under right conditions (usually anaerobic following injury) they germinate and bacilli grow
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| − | **Toxin damages capillaries -> serosanguinous exudate
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| − | **Muscle necrosis due to gas producing bacteria -> emphysaema and crepitus
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| − | *Grossly:
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| − | **Early stages
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| − | ***At muscle periphery
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| − | ***Dark red
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| − | ***Distended by serous or serosanguinous exudate
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| − | ***Wet cut surface
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| − | **Old stages
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| − | ***Centre of lesion is full of gas bubbles, porous, dry, reddish black
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| − | ***Rancid odour
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| − | *Histologically:
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| − | **Early stages
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| − | ***Separation of myofibres by exudate
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| − | ***[[General Pathology - Necrosis#Coagulation Necrosis|Coagulative necrosis]]
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| − | ***No nuclei
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| − | **Old stage
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| − | ***Fragmented muscle fibres separated by gas bubbles
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| − | ***Gram positive bacilli may be found in clumps
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| − | | |
| − | | |
| − | ====[[General Pathology - Necrosis#Gas Gangrene|Gas gangrene]]====
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| − | | |
| − | *Causative agents: [[Clostridium species|''Clostridium septicum, C. novyi, C. perfringens, C. sordelli'']]
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| − | *Normally in soil
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| − | *Bacteria gain entry as spores via penetrating wounds
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| − | *Serohaemorrhagic myositis
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| − | *If only subcutis and fascia are involved - '''malignant oedema'''
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| − | *Toxaemia and septicaemia -> rapid death
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| − | | |
| − | | |
| − | ====[[Tongue - Pathology#Actinobacillosis|Wooden tongue]]====
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| − | | |
| − | *Also called '''Actinobacillosis'''
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| − | *Caused by [[Actinobacillus species|''Actinobacillus lignieresii'']]
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| − | *Usually due to direct penetration into [[Tongue - Pathology - Anatomy & Physiology|tongue]] of cattle
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| − | *Small granulomatous lesions containing 'sulfa granules' of large numbers of gram-negative rods
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| − | | |
| − | ====Tuberculosis====
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| − | | |
| − | *Caused by [[Mycobacteria spp.|''Mycobacterium bovis'']]
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| − | *Grossly:
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| − | **Yellowish spherical nodules
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| − | **[[General Pathology - Necrosis#Caseation Necrosis|Caseous content]]
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| − | **Fibrous capsule usually
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| − | *Histologically:
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| − | **Granuloma
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| − | **Central necrosis
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| − | **Epitheliod and giant cells at periphery
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| − | | |
| − | | |
| − | ====[[Actinomycetes|''Actinomycosis bovis'']]====
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| − | *"Lumpy jaw"
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| − | *May extend to muscles, especially masseters, from [[Bones Inflammatory - Pathology#Osteomyelitis|osteomyelitis]]
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| − | *Histologically:
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| − | **Caseous or suppurative centres of lesions
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| − | **Epithelioid and giant cells at periphery
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| − | **'Sulfa granules' at centre - gram-positive branching rods
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| − | | |
| − | ====Botryomycosis====
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| − | | |
| − | *Caused by [[Staphylococcus spp.|''Staphylococcus aureus'']]
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| − | *Occurs in horses and pigs usually due to wounds
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| − | *Lowgrade persistent infection -> granulomatous lesions
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| − | *Grossly:
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| − | **Hard nodules with fibrous capsule in muscles
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| − | **Contain yellow-brown pus and granules
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| − | *Histologically:
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| − | **Encapsulated granulomatous lesions
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| − | **Central club colonies
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| − | **Staphylococci are present
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| − | | |
| − | | |
| − | ===Viral myositis===
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| − | | |
| − | *Rare in the UK
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| − | | |
| − | ====Porcine encephalomyelitis====
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| − | | |
| − | *Caused by [[Coronaviridae|Coronavirus]]
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| − | *May cause multifocal myofibre necrosis + focal interstitial and perivascular lymphocyte, macrophage and neutrophil infiltration
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| − | | |
| − | | |
| − | ====Foot and Mouth disease====
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| − | | |
| − | *Caused by [[Picornaviridae|Apthovirus]]
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| − | *Main presentation are vesicles
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| − | *May also involve skeletal and heart muscle
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| − | *Grossly:
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| − | **Yellow streaks and grey foci
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| − | *Histologically:
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| − | **Segmental myofibre [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
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| − | **Infiltration of lymphocytes and neutrophils
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| − | | |
| − | | |
| − | ====Bluetongue====
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| − | | |
| − | *Caused by [[Reoviridae|bluetongue virus of family Reoviridae]]
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| − | *Non-contagious
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| − | *Insect-borne
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| − | *Causes vasculitis, especially in oral cavity
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| − | *Grossly:
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| − | **Infarctions -> necrosis
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| − | **Haemorrhage
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| − | *Histologically:
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| − | **Necrosis -> calcification or regeneration (depends on age of lesion)
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| − | | |
| − | | |
| − | ===Parasitic myositis===
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| − | [[Image:taenia ovis cysticerci.jpg|right|thumb|100px|<small><center>''T. ovis'' cysticerci (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | [[Image:Sarcocyst in muscle.jpg|right|thumb|100px|<small><center>Sarcocyst (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | *Rare in domestic animals
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| − | | |
| − | | |
| − | ====Nematodes====
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| − | | |
| − | *[[Trichinelloidea|'''''Trichinella''''']] larvae
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| − | **Particularly in pigs and dogs
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| − | **Public health and economic importance
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| − | **''T. spiralis'' affecting dogs, pigs, cats and humans is most common in hotter climates
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| − | **Larvae distend myofibres
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| − | **May be seen grossly if dead and calcified
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| − | **Predilection for active muscles, ''e.g.'' diaphragm, intercostal, masseter and tongue muscles
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| − | **Histologically:
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| − | ***Focal myositis - neutrophils, lymphocytes, eosinophils
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| − | | |
| − | *[[Ancylostomatoidea|''Ancylostoma'']] larvae
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| − | **Cause inflammation and [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
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| − | *[[Ascaridoidea|Ascarid]] larvae
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| − | *[[Dirofilaria immitis|''Dirofilaria immitis'']] in dogs causing ischaemic myopathy due to [[Muscles Degenerative - Pathology#Ischaemia|infartcs]]
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| − | | |
| − | | |
| − | ====Cestodes====
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| − | | |
| − | *[[Taenia|''Taenia solium, '']] - cysticercosis in swine and humans
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| − | *[[Taenia|''T. ovis'']] - cysticercosis in sheep
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| − | *[[Taenia|''T. saginata'']] in cattle cysticercosis
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| − | *[[Taenia|''Multiceps serialis'']] in rabbits, primates coenurosis
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| − | *[[Echinococcus|''Echinococcus granulosus'']] hydatid disease in herbivores and humans
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| − | | |
| − | ====Protozoa====
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| − | | |
| − | *[[Tissue cyst-forming coccidia|'''''Toxoplasma gondii''''']]
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| − | **Cats as final hosts
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| − | **Intermediate hosts, birds and mammals have tachyzoites throughout body, infrequently in skeletal muscle
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| − | **Histologically:
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| − | ***Multifocal [[Muscles Degenerative - Pathology#Necrosis|necrosis]] of myofibres
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| − | ***Lymphocyte and plasma cell infiltration
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| − | ***In later stages bradyzoite cysts
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| − | *[[Tissue cyst-forming coccidia|'''''Neospora caninum''''']]
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| − | **Necrotising inflammation of muscles
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| − | **Myositis more severe than in toxoplasmosis
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| − | *[[Tissue cyst-forming coccidia|'''''Sarcocystis''''']]
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| − | **Histologically:
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| − | ***Merozoites causing focal and segmental [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
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| − | ***May involve [[Muscles Degenerative - Pathology#Calcification|mineralisation]]
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| − | ***Non-purulent myositis with plasma cells, lymphocytes and macrophages
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| − | **Diaphragm and masseters most severely affected
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| − | *[[Bones Hyperplastic and Neoplastic - Pathology#Hepatozoon|'''''Hepatozoon americanum''''']]
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| − | **Develop cysts in skeletal muscle of dogs and cats
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| − | **May be accompanied by pyogranulomatous myositis - macrophages and neutrophils mainly with occasional other cells
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| − | *'''''Trypanosoma'''''
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| − | **Infrequent muscle lesions with mononuclear infiltrates
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| − | **Dogs, cats and pigs are affected
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| − | **Parasites lie between myofilaments
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| − | **May cause fibre degeneration
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| − | *'''''Babesia bovis'''''
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| − | **In cattle
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| − | **Infrequent muscle [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
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| − | | |
| − | | |
| − | ====Arthropods====
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| − | | |
| − | *Dipterious larvae causing myiasis
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| − | *[[Insecta|''Hypoderma'' spp.]] in cattle
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| − | **May occasionally burrow into muscle
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| − | | |
| − | | |
| − | ===Immune-mediated myositis===
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| − | | |
| − | ====Masticatory muscle myositis (MMM)====
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| − | | |
| − | *Occurs in dogs
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| − | *Tends to affect the masseter and temporalis muscles
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| − | *Autoantibodies selectively attack muscles of mastication (type IIM fibres)
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| − | *Acute stage = eosinophilic myositis
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| − | **Extremely swollen, painful, hard masticatory muscles
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| − | *Chronic stage = atrophic myositis
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| − | **Atrophy may occur without previous acute stage
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| − | *Grossly:
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| − | **Bilateral but not necessarily symmetrical
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| − | **At first, enlarged and oedematous muscles becominf dark red, firm with reddish streaks and yellowiss foci
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| − | *Histologically:
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| − | **Acute lesions:
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| − | ***Mainly eosinophilic infiltrate, few lymphocytes, monocytes and plasma cells
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| − | ***In recurrent disease plasma cells predominate
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| − | ***[[Muscles Degenerative - Pathology#Necrosis|Necrotic]] myofibres, [[Muscles Degenerative - Pathology#Atrophy|atrophy]] and attempted [[Muscle Regeneration - Anatomy & Physiology|regeneration]]
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| − | **Chronic stage:
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| − | ***[[Muscles Degenerative - Pathology#Atrophy|Atrophy]] predominates
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| − | ***Fasciculi are shrunken
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| − | ***Condensation of stroma -> enlarged endomysium
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| − | ***Focal plasma cell and lymphocyte infiltration
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| − | | |
| − | | |
| − | ====[[Muscles Developmental - Pathology#Canine dermatomyositis|Canine dermatomyositis]]====
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| − | | |
| − | | |
| − | ===Idiopathic myositis===
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| − | | |
| − | ====Canine polymyositis====
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| − | | |
| − | *DOES NOT include MMM above
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| − | *Rare
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| − | *Clinical signs:
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| − | **Muscle pain
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| − | **Fever
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| − | **Weakness, particularly in hind limbs
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| − | *Grossly:
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| − | **Inflammation is accompanied by muscle necrosis and regeneration
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| − | *Histologically:
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| − | **Inflammatory foci with lymphocytes, plasma cells and occasionally eosinophils
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| − | *Possibly immunological cause
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| − | *Single biopsy may not be enough to make the diagnosis as it tends to be multifocal and disseminated
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| − | *Lesions similar to some infectious causes (such as [[Tissue cyst-forming coccidia|''Toxoplasma gondii'']])
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| − | | |
| − | | |
| − | ====Canine bilateral extraocular polymyositis====
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| − | | |
| − | *In Golden retrievers
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| − | *Very rare
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| − | *Clinical signs:
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| − | **Acute bilateral exophthalmos
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| − | *Involves only extraocular muscles except for retractor blbi
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| − | *Grossly:
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| − | **Swollen and pale extraocular muscles
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| − | *Histologically:
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| − | **Sterile myositis
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| − | **Multifocal necrosis of myofibres
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| − | **Lymphocytic, histiocytic and plasmacytic infiltrate with few neutrophils
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| − | | |
| − | | |
| − | ====Bovine and ovine eosinophilic myositis====
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| − | | |
| − | *Unknown aetiology
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| − | *Major cell involved is eosinphil
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| − | *Usually noticed at slaughter - green muscle discoloration
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| − | *May be caused by degenteration of [[Tissue cyst-forming coccidia|''Sarcocystis'' spp.]]
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| − | *Grossly:
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| − | **Green discolored areas, well demarcated
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| − | **Mostly in muscles of back and thighs
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| − | *Histologically:
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| − | **Massive eosinophil infiltration
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| − | **Muscle fibres may degenerate
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| − | **In old lesions - endimysial fibrosis, myofibre atrophy, some regeneration, lymphocytes, plasma cells, macrophages and few eosinophils
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| − | **Capsule may form
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