Difference between revisions of "Black Leg"

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Also known as: '''''Blackquarter
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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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{| cellpadding="10" cellspacing="0" border="1"
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| Also known as:
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| '''Blackquarter
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==Introduction==
 
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[[Image:Black leg myositis.jpg|right|thumb|300px|<small><center>Blackleg myositis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 
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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.
 
  
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==Signalment==
 
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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.
 
  
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In sheep, cases typically occur following some form of injury such as shearing cuts, docking or castration.
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==Description==
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A bacterial disease affecting cattle and sheep caused by [[Clostridium chauvoei|''Clostridium chauvoei'']]. Latent spores of this organism are deposited in the muscle and liver of ruminants via the circulation resulting in oedematous and crepitant swellings of the muscles.  
  
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Tends to affect animals in the summer months.
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==Signalment==
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In cattle it is typically beef breeds who are affeceted particularly animals in good health and gaining weight quickly. 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
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In cattle, blackleg infection is endogenous, in contrast to malignant edema ( Malignant Edema). Lesions develop without any history of wounds, although bruising or excessive exercise may precipitate some cases. Commonly, the animals that contract blackleg are of the beef breeds, in excellent health, gaining weight, and usually the best animals of their group. Outbreaks occur in which a few new cases are found each day for several days. Most cases are seen in cattle from 6-24 mo old, but thrifty calves as young as 6 wk and cattle as old as 10-12 yr may be affected. The disease usually occurs in summer and fall and is uncommon during the winter. In sheep, the disease is not restricted to the young, and most cases follow some form of injury such as shearing cuts, docking, crutching, or castration. Endogenous blackleg in sheep is uncommon in the USA; it is much more common in New Zealand where blackleg is seen more frequently in sheep than in cattle.  
  
 
==Diagnosis==
 
==Diagnosis==
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Diagnosis is made on clinical signs and muscle biopsy.
 
  
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==History and Clinical Signs==
 
==History and Clinical Signs==
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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.
 
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==Pathology==
 
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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.
 
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==Treatment==
 
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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.
 
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==Prognosis==
 
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Poor, clinical cases can be treated with penicillin however this is rarely successful.
 
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==Literature Search==
 
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[[File:CABI logo.jpg|left|90px]]
 
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Use these links to find recent scientific publications via CAB Abstracts (log in required unless accessing from a subscribing organisation).
 
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<br><br><br>
 
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[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]
 
  
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==References==
 
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Merck & Co (2008) '''The Merck Veterinary Manual''' (Eighth Edition) Merial
 
  
  
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{{review}}
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*Causative agent: ''[[Clostridium chauvoei]]''
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[[Category:Musculoskeletal Diseases - Sheep]][[Category:Liver Diseases - Sheep]][[Category:Musculoskeletal Diseases - Cattle]][[Category:Liver Diseases - Cattle]][[Category:Bacterial Myositis]]
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*May affect the fattest cattle at pasture in the summer
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[[Category:Brian Aldridge reviewing]]
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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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[[Category:Sheep]][[Category:To_Do_-_Caz]]

Revision as of 20:40, 18 July 2010

Blackleg myositis (Image sourced from Bristol Biomed Image Archive with permission)
Also known as: Blackquarter



Description

A bacterial disease affecting cattle and sheep caused by Clostridium chauvoei. Latent spores of this organism are deposited in the muscle and liver of ruminants via the circulation resulting in oedematous and crepitant swellings of the muscles.


Signalment

In cattle it is typically beef breeds who are affeceted particularly animals in good health and gaining weight quickly. 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 cattle, blackleg infection is endogenous, in contrast to malignant edema ( Malignant Edema). Lesions develop without any history of wounds, although bruising or excessive exercise may precipitate some cases. Commonly, the animals that contract blackleg are of the beef breeds, in excellent health, gaining weight, and usually the best animals of their group. Outbreaks occur in which a few new cases are found each day for several days. Most cases are seen in cattle from 6-24 mo old, but thrifty calves as young as 6 wk and cattle as old as 10-12 yr may be affected. The disease usually occurs in summer and fall and is uncommon during the winter. In sheep, the disease is not restricted to the young, and most cases follow some form of injury such as shearing cuts, docking, crutching, or castration. Endogenous blackleg in sheep is uncommon in the USA; it is much more common in New Zealand where blackleg is seen more frequently in sheep than in cattle.

Diagnosis

History and Clinical Signs

  • 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
    • Old stage
      • Fragmented muscle fibres separated by gas bubbles
      • Gram positive bacilli may be found in clumps
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