WikiVet English

Changes

Muscles Inflammatory - Pathology (view source)

Revision as of 20:15, 18 August 2008

10,652 bytes added ,  20:15, 18 August 2008
no edit summary
Line 9: Line 9:  
}}
 
}}
 
<br>
 
<br>
 +
==Myositis==
 +
 +
*Inflammation of muscle
 +
 +
 +
===Bacterial myositis===
 +
 +
*Bacteria gain entry via:
 +
**Direct penetration
 +
**Blood stream
 +
**Extension
 +
*Lesions caused:
 +
**Suppurative
 +
**Serosanguinous
 +
**Granulomatous
 +
 +
 +
====Abscesses====
 +
 +
*Caused by pyogenic bacteria
 +
*Usually:
 +
**[[Arcanobacter pyogenes|''Arcanobacterium pyogenes'']] in sheep and cattle
 +
**[[Respiratory Bacterial Infections - Pathology#Strangles|''Streptococcus equi'']] in horses
 +
**[[Corynebacterium species|''Corynebacterium pseudotuberculosis'']] in sheep and goats
 +
**[[Pasteurella species and Mannheimia haemolytica|''Pasteurella multocida'']] causes cellulitis in cats
 +
*Usually localised suppuration and necrosis of myofibres
 +
*Occasionally my spread via the fascia
 +
 +
 +
====Black leg====
 +
[[Image:Black leg myositis.jpg|right|thumb|100px|<small><center>Blackleg myositis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
 +
*Causative agent: [[Clostridium species|''Clostridium chauvoei'']]
 +
*May affect the fattest cattle at pasture in the summer
 +
*Rapid toxaemia -> death
 +
*If clinical signs observed:
 +
**Toxaemia -> pyrexia, depression, [[Lungs Circulatory - Pathology#Pulmonary oedema|pulmonary oedema]], circulatory collapse
 +
**Muscle lesions -> lameness, swollen hot muscles later becoming cool as necrosis sets in
 +
*Pathogenesis:
 +
**Spores gain entry to GI tract -> blood -> muscle -> lie latent
 +
**Under right conditions (usually anaerobic following injury) they germinate and bacilli grow
 +
**Toxin damages capillaries -> serosanguinous exudate
 +
**Muscle necrosis due to gas producing bacteria -> emphysaema and crepitus
 +
*Grossly:
 +
**Early stages
 +
***At muscle periphery
 +
***Dark red
 +
***Distended by serous or serosanguinous exudate
 +
***Wet cut surface
 +
**Old stages
 +
***Centre of lesion is full of gas bubbles, porous, dry, reddish black
 +
***Rancid odour
 +
*Histologically:
 +
**Early stages
 +
***Separation of myofibres by exudate
 +
***[[General Pathology - Necrosis#Coagulation Necrosis|Coagulative necrosis]]
 +
***No nuclei
 +
**Old stage
 +
***Fragmented muscle fibres separated by gas bubbles
 +
***Gram positive bacilli may be found in clumps
 +
 +
 +
====[[General Pathology - Necrosis#Gas Gangrene|Gas gangrene]]====
 +
 +
*Causative agents: [[Clostridium species|''Clostridium septicum, C. novyi, C. perfringens, C. sordelli'']]
 +
*Normally in soil
 +
*Bacteria gain entry as spores via penetrating wounds
 +
*Serohaemorrhagic myositis
 +
*If only subcutis and fascia are involved - '''malignant oedema'''
 +
*Toxaemia and septicaemia -> rapid death
 +
 +
 +
====[[Oral Cavity - Tongue#Actinobacillosis|Wooden tongue]]====
 +
 +
*Also called '''Actinobacillosis'''
 +
*Caused by [[Actinobacillus species|''Actinobacillus lignieresii'']]
 +
*Usually due to direct penetration into [[Oral Cavity - Tongue - Anatomy & Physiology|tongue]] of cattle
 +
*Small granulomatous lesions containing 'sulfa granules' of large numbers of gram-negative rods
 +
 +
====Tuberculosis====
 +
 +
*Caused by [[Mycobacteria spp.|''Mycobacterium bovis'']]
 +
*Grossly:
 +
**Yellowish spherical nodules
 +
**[[General Pathology - Necrosis#Caseation Necrosis|Caseous content]]
 +
**Fibrous capsule usually
 +
*Histologically:
 +
**Granuloma
 +
**Central necrosis
 +
**Epitheliod and giant cells at periphery
 +
 +
 +
====[[Actinomycetes|''Actinomycosis bovis'']]====
 +
 +
*May extend to muscles, especially masseters, from [[Bones Inflammatory - Pathology#Osteomyelitis|osteomyelitis]]
 +
*Histologically:
 +
**Caseous or suppurative centres of lesions
 +
**Epithelioid and giant cells at periphery
 +
**'Sulfa granules' at centre - gram-positive branching rods
 +
 +
 +
====Botryomycosis====
 +
 +
*Caused by [[Staphylococcus spp.|''Staphylococcus aureus'']]
 +
*Occurs in horses and pigs usually due to wounds
 +
*Lowgrade persistent infection -> granulomatous lesions
 +
*Grossly:
 +
**Hard nodules with fibrous capsule in muscles
 +
**Contain yellow-brown pus and granules
 +
*Histologically:
 +
**Encapsulated granulomatous lesions
 +
**Central club colonies
 +
**Staphylococci are present
 +
 +
 +
===Viral myositis===
 +
 +
*Rare in the UK
 +
 +
====Porcine encephalomyelitis====
 +
 +
*Caused by [[Coronaviridae|Coronavirus]]
 +
*May cause multifocal myofibre necrosis + focal interstitial and perivascular lymphocyte, macrophage and neutrophil infiltration
 +
 +
 +
====Foot and Mouth disease====
 +
 +
*Caused by [[Picornaviridae|Apthovirus]]
 +
*Main presentation are vesicles
 +
*May also involve skeletal and heart muscle
 +
*Grossly:
 +
**Yellow streaks and grey foci
 +
*Histologically:
 +
**Segmental myofibre [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
 +
**Infiltration of lymphocytes and neutrophils
 +
 +
 +
====Bluetongue====
 +
 +
*Caused by [[Reoviridae|bluetongue virus of family Reoviridae]]
 +
*Non-contagious
 +
*Insect-borne
 +
*Causes vasculitis, especially in oral cavity
 +
*Grossly:
 +
**Infarctions -> necrosis
 +
**Haemorrhage
 +
*Histologically:
 +
**Necrosis -> calcification or regeneration (depends on age of lesion)
 +
 +
 +
===Parasitic myositis===
 +
[[Image:taenia ovis cysticerci.jpg|right|thumb|100px|<small><center>''T. ovis'' cysticerci (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
[[Image:Sarcocyst in muscle.jpg|right|thumb|100px|<small><center>Sarcocyst (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
*Rare in domestic animals
 +
 +
 +
====Nematodes====
 +
 +
*[[Trichinelloidea|'''''Trichinella''''']] larvae
 +
**Particularly in pigs and dogs
 +
**Public health and economic importance
 +
**''T. spiralis'' affecting dogs, pigs, cats and humans is most common in hotter climates
 +
**Larvae distend myofibres
 +
**May be seen grossly if dead and calcified
 +
**Predilection for active muscles, ''e.g.'' diaphragm, intercostal, masseter and tongue muscles
 +
**Histologically:
 +
***Focal myositis - neutrophils, lymphocytes, eosinophils
 +
 +
*[[Ancylostomatoidea|''Ancylostoma'']] larvae
 +
**Cause inflammation and [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
 +
*[[Ascaridoidea|Ascarid]] larvae
 +
*[[Dirofilaria immitis|''Dirofilaria immitis'']] in dogs causing ischaemic myopathy due to [[Muscles Degenerative - Pathology#Ischaemia|infartcs]]
 +
 +
 +
====Cestodes====
 +
 +
*[[Taenia|''Taenia solium, '']] - cysticercosis in swine and humans
 +
*[[Taenia|''T. ovis'']] - cysticercosis in sheep
 +
*[[Taenia|''T. saginata'']] in cattle cysticercosis
 +
*[[Taenia|''Multiceps serialis'']] in rabbits, primates coenurosis
 +
*[[Echinococcus|''Echinococcus granulosus'']] hydatid disease in herbivores and humans
 +
 +
====Protozoa====
 +
 +
*[[Tissue cyst-forming coccidia|'''''Toxoplasma gondii''''']]
 +
**Cats as final hosts
 +
**Intermediate hosts, birds and mammals have tachyzoites throughout body, infrequently in skeletal muscle
 +
**Histologically:
 +
***Multifocal [[Muscles Degenerative - Pathology#Necrosis|necrosis]] of myofibres
 +
***Lymphocyte and plasma cell infiltration
 +
***In later stages bradyzoite cysts
 +
*[[Tissue cyst-forming coccidia|'''''Neospora caninum''''']]
 +
**Necrotising inflammation of muscles
 +
**Myositis more severe than in toxoplasmosis
 +
*[[Tissue cyst-forming coccidia|'''''Sarcocystis''''']]
 +
**Histologically:
 +
***Merozoites causing focal and segmental [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
 +
***May involve [[Muscles Degenerative - Pathology#Calcification|mineralisation]]
 +
***Non-purulent myositis with plasma cells, lymphocytes and macrophages
 +
**Diaphragm and masseters most severely affected
 +
*[[Bones Hyperplastic and Neoplastic - Pathology#Hepatozoon|'''''Hepatozoon americanum''''']]
 +
**Develop cysts in skeletal muscle of dogs and cats
 +
**May be accompanied by pyogranulomatous myositis - macrophages and neutrophils mainly with occasional other cells
 +
*'''''Trypanosoma'''''
 +
**Infrequent muscle lesions with mononuclear infiltrates
 +
**Dogs, cats and pigs are affected
 +
**Parasites lie between myofilaments
 +
**May cause fibre degeneration
 +
*'''''Babesia bovis'''''
 +
**In cattle
 +
**Infrequent muscle [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
 +
 +
 +
====Arthropods====
 +
 +
*Dipterious larvae causing myiasis
 +
*[[Insecta|''Hypoderma'' spp.]] in cattle
 +
**May occasionally burrow into muscle
 +
 +
 +
===Immune-mediated myositis===
 +
 +
====Masticatory muscle myositis (MMM)====
 +
 +
*Occurs in dogs
 +
*Tends to affect the masseter and temporalis muscles
 +
*Autoantibodies selectively attack muscles of mastication (type IIM fibres)
 +
*Acute stage = eosinophilic myositis
 +
**Extremely swollen, painful, hard masticatory muscles
 +
*Chronic stage = atrophic myositis
 +
**Atrophy may occur without previous acute stage
 +
*Grossly:
 +
**Bilateral but not necessarily symmetrical
 +
**At first, enlarged and oedematous muscles becominf dark red, firm with reddish streaks and yellowiss foci
 +
*Histologically:
 +
**Acute lesions:
 +
***Mainly eosinophilic infiltrate, few lymphocytes, monocytes and plasma cells
 +
***In recurrent disease plasma cells predominate
 +
***[[Muscles Degenerative - Pathology#Necrosis|Necrotic]] myofibres, [[Muscles Degenerative - Pathology#Atrophy|atrophy]] and attempted [[Muscles - normal#Regeneration|regeneration]]
 +
**Chronic stage:
 +
***[[Muscles Degenerative - Pathology#Atrophy|Atrophy]] predominates
 +
***Fasciculi are shrunken
 +
***Condensation of stroma -> enlarged endomysium
 +
***Focal plasma cell and lymphocyte infiltration
 +
 +
 +
====[[Muscles Developmental - Pathology#Canine dermatomyositis|Canine dermatomyositis]]====
 +
 +
 +
===Idiopathic myositis===
 +
 +
====Canine polymyositis====
 +
 +
*DOES NOT include MMM above
 +
*Rare
 +
*Clinical signs:
 +
**Muscle pain
 +
**Fever
 +
**Weakness, particularly in hind limbs
 +
*Grossly:
 +
**Inflammation is accompanied by muscle necrosis and regeneration
 +
*Histologically:
 +
**Inflammatory foci with lymphocytes, plasma cells and occasionally eosinophils
 +
*Possibly immunological cause
 +
*Single biopsy may not be enough to make the diagnosis as it tends to be multifocal and disseminated
 +
*Lesions similar to some infectious causes (such as [[Tissue cyst-forming coccidia|''Toxoplasma gondii'']])
 +
 +
 +
====Canine bilateral extraocular polymyositis====
 +
 +
*In Golden retrievers
 +
*Very rare
 +
*Clinical signs:
 +
**Acute bilateral exophthalmos
 +
*Involves only extraocular muscles except for retractor blbi
 +
*Grossly:
 +
**Swollen and pale extraocular muscles
 +
*Histologically:
 +
**Sterile myositis
 +
**Multifocal necrosis of myofibres
 +
**Lymphocytic, histiocytic and plasmacytic infiltrate with few neutrophils
 +
 +
 +
====Bovine and ovine eosinophilic myositis====
 +
 +
*Unknown aetiology
 +
*Major cell involved is eosinphil
 +
*Usually noticed at slaughter - green muscle discoloration
 +
*May be caused by degenteration of [[Tissue cyst-forming coccidia|''Sarcocystis'' spp.]]
 +
*Grossly:
 +
**Green discolored areas, well demarcated
 +
**Mostly in muscles of back and thighs
 +
*Histologically:
 +
**Massive eosinophil infiltration
 +
**Muscle fibres may degenerate
 +
**In old lesions - endimysial fibrosis, myofibre atrophy, some regeneration, lymphocytes, plasma cells, macrophages and few eosinophils
 +
**Capsule may form
Retrieved from "https://en.wikivet.net/Special:MobileDiff/28909"