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| − | ====Black leg==== | + | ====[[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>]]
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| − | *Causative agent: ''[[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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| − | ***[[Necrosis - Pathology#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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| | ====[[Necrosis - Pathology#Gas Gangrene|Gas gangrene]]==== | | ====[[Necrosis - Pathology#Gas Gangrene|Gas gangrene]]==== |