Difference between revisions of "Black Leg"

Revision as of 22:24, 8 July 2010

Blackleg myositis (Image sourced from Bristol Biomed Image Archive with permission)

Causative agent: Clostridium chauvoei
May affect the fattest cattle at pasture in the summer
Rapid toxaemia -> death
If clinical signs observed:
- Toxaemia -> pyrexia, depression, 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
  - Coagulative necrosis
  - No nuclei
- Old stage
  - Fragmented muscle fibres separated by gas bubbles
  - Gram positive bacilli may be found in clumps

@@ Line 1: / Line 1: @@
-Also known as: '''''Blackquarter
+[[Image:Black leg myositis.jpg|right|thumb|100px|<small><center>Blackleg myositis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
-==Introduction==
+*Causative agent: ''[[Clostridium chauvoei]]''
-[[Image:Black leg myositis.jpg|right|thumb|300px|<small><center>Blackleg myositis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
+*May affect the fattest cattle at pasture in the summer
-A bacterial disease affecting cattle and sheep caused by [[Clostridium chauvoei|''Clostridium chauvoei'']]. Spores pass through the wall of the GI tract and via the bloodstream enter the muscle and liver where they then lie latent. This results in oedematous and crepitant swelling of the muscles. Under the correct conditions (usually anaerobic following injury) they germinate and bacilli grow. Toxins damage the capillaries causing a severe necrotising myositis.
+*Rapid toxaemia -> death
+*If clinical signs observed:
-==Signalment==
+**Toxaemia -> pyrexia, depression, [[Lungs Circulatory - Pathology#Pulmonary oedema|pulmonary oedema]], circulatory collapse
-In cattle it is typically beef breeds who are affected particularly animals in good health and good body condition. More frequently occurs in cattle between 6-24 months old but can affect animals of any age. In some animals lesions occur following muscle trauma, which is thought to activate latent spores in the muscle.
+**Muscle lesions -> lameness, swollen hot muscles later becoming cool as necrosis sets in
+*Pathogenesis:
-In sheep, cases typically occur following some form of injury such as shearing cuts, docking or castration.
+**Spores gain entry to GI tract -> blood -> muscle -> lie latent
+**Under right conditions (usually anaerobic following injury) they germinate and bacilli grow
-Tends to affect animals in the summer months.
+**Toxin damages capillaries -> serosanguinous exudate
+**Muscle necrosis due to gas producing bacteria -> emphysaema and crepitus
-==Diagnosis==
+*Grossly:
-Diagnosis is made on clinical signs and muscle biopsy.
+**Early stages
+***At muscle periphery
-==History and Clinical Signs==
+***Dark red
-The bacteria can cause rapid toxaemia resulting in sudden death, however, if clinical signs do occur these can include toxaemia, pyrexia, depression, [[Pulmonary Oedema|pulmonary oedema]], circulatory collapse lameness and swollen hot muscles which later become cool as necrosis occurs.
+***Distended by serous or serosanguinous exudate
+***Wet cut surface
-==Pathology==
+**Old stages
-Affected muscle is black, dry, infiltrated with small bubbles, distended by serous or serosanguinous exudate and often has a rancid smell. The lesions can be present in any muscle including the tongue or diaphragm and it is not unusual to find clumps of gram positive bacteria in affected muscle. Often in sheep, lesions are deep and quite small. Suspected cases can be confirmed using demonstration of ''C. chauvoei'' in diseased muscle using the fluorescent antibody test on smears produced from the primary lesion.
+***Centre of lesion is full of gas bubbles, porous, dry, reddish black
+***Rancid odour
-==Treatment==
+*Histologically:
-Vaccination can prevent black leg in cattle and sheep. In the face of an outbreak all susceptible animals should be treated with penicillin and vaccinated.
+**Early stages
+***Separation of myofibres by exudate
-==Prognosis==
+***[[Necrosis - Pathology#Coagulation Necrosis|Coagulative necrosis]]
-Poor, clinical cases can be treated with penicillin however this is rarely successful.
+***No nuclei
+**Old stage
-==Literature Search==
+***Fragmented muscle fibres separated by gas bubbles
-[[File:CABI logo.jpg|left|90px]]
+***Gram positive bacilli may be found in clumps
+[[Category:Sheep]][[Category:To_Do_-_Caz]]
-Use these links to find recent scientific publications via CAB Abstracts (log in required unless accessing from a subscribing organisation).
-<br><br><br>
-[http://www.cabdirect.org/search.html?q=%28%28title%3A%28%22Clostridium+chauvoei%22%29+AND+sc%3A%22ve%22%29%29+OR+%28%28title%3A%28%22blackleg%22%29+OR+title%3A%28%22black+leg%22%29+OR+title%3A%28%22black+quarter%22%29+OR+title%3A%28%22blackquarter%22%29+AND+sc%3A%22ve%22%29%29 Blackleg publications]
-==References==
-Merck & Co (2008) '''The Merck Veterinary Manual''' (Eighth Edition) Merial
-{{review}}
-[[Category:Musculoskeletal Diseases - Sheep]][[Category:Liver Diseases - Sheep]][[Category:Musculoskeletal Diseases - Cattle]][[Category:Liver Diseases - Cattle]][[Category:Bacterial Myositis]]
-[[Category:Brian Aldridge reviewing]]

Difference between revisions of "Black Leg"

Revision as of 22:24, 8 July 2010

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