Difference between revisions of "Anthrax"

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|link = Factoid - Anthrax}}
 
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Also known as: '''''Anthracosis
 
  
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==Introduction==
 
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[[File:Bacillus anthracis Gram.jpg|right|thumb|250px|<small><center> photomicrograph of ''Bacillus anthracis'' bacteria using Gram-stain technique. (CDC unknown, Wikimedia commons)</center></small>]]
 
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Anthrax is a serious, often fatal zoonotic disease of wild and domestic mammals caused by the spore-forming bacterium ''[[Bacillus anthracis]]''. The disease has been reported worldwide (particularly in the tropical countries) and often occurs in outbreaks. The disease primarily affects herbivores but humans may be infected via contact with infected animal tissues, exposure to high concentrations of spores or contacted with infected animals.
 
  
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==Pathogenesis==
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==Description==
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The infected host sheds ''B. anthracis'' bacilli into the environment which sporulate on exposure to air. These spores are highly resistant and can survive in the environment for many years.  Grazing animals may become infected if ingestion of a large number of spores occurs. Following inhalation, germination and localised multiplication of the spores takes place. Spread via the lymphatics and blood stream then occurs, leading to massive septicaemia. In addition to the above routes of infection, [[:Category:Biting Flies|biting flies]] appear to have a role in transmission of spores in areas of endemic disease. Inhalation of dust-borne spores may also be of importance in the pathogenesis of the disease.
 
  
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In general, carnivores are more resistant to disease than herbivores. In herbivores the disease commonly presents as a peracute onset septicaemia with a high mortality rate. In dogs, humans and pigs however, the onset is less acute.
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Anthrax is a zoonotic disease caused by the spore-forming bacterium [[Bacillus anthracis]].
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*Clinical signs:
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**Cattle/sheep:
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***Fatal peracute septicaemia
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***Animals usually found dead
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***Pyrexia, depression, congested mucous membranes and petechiae before death
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***Abortion, subcutaneous oedema and dysentry in animals surviving more that one day
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**Pigs:
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***Subacute anthrax with oedematous swelling of throat, head and regional lymph nodes
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***Intestinal form with high mortality - dysentry due to haemorrhagic enteric lesions
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***[[Peritonitis#In pigs|Peritonitis]]
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**Horses:
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***Subacute anthrax with subcutaneous oedema of thorax, abdomen and legs following entrance of spores into abrasions
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***Septicaemia with colic and dysentry due to haemorrhagic enteritis from ingestion of spores; ecchymoses and splenomegaly
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**Dogs
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***Rarely affected, but similar disease to that found in pigs
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**Humans
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***Cutaneous anthrax - localised lesion from entrance into abrasion which can cause septicaemia
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***Pulmonary anthrax - inhalation of spores
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***Intestinal anthrax - ingestion of infective material
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*Diagnosis:
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**Post mortem: bloat, incomplete rigor mortis, ecchymoses, oedema, dark unclotted blood from orifices, blooy fluid in body cavities, splenomegaly
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**Blood smear from an ear or tail vein of ruminants, or peritoneal fluid from pigs stained with polychrome methylene blue
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**Chains of square-ended blue rods surrounded by mauve capsules
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**Culture on blood and MacConkey agar (no growth on MacConkey)
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**Biochemical tests
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*Treatment:
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**High doses of penicillin G or oxytetracylcine
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*Control:
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**Report suspected cases - notifiable
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**Spores destroyed by sterilisation
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**Endemic regions:
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***Live Sterne spore vaccine which produces toxin but has no capsule, therefore is non-pathogenic; stimulates protective antibody
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***Chemoprophylaxis with long-acting penicillin
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**Non-endemic regions after an outbreak:
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***Movement restrictions
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***Footbath with sporicidal disinfectant
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***Fumigate buildings with formaldehyde
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***Dispose carcases and contaminated material
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***Isolate in-contact animals
  
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==Clinical Signs==
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[[Category:Cattle]][[Category:Sheep]][[Category:Pig]][[Category:Dog]]
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===Ruminants and Horses===
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[[Category:Alimentary_Disorders_-_Horse]]
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The incubation period of the disease is approximately three to seven days. Often animals may be '''discovered dead''' in the field before any clinical signs have been observed. In general, in non-immunised ruminants and horses the disease is characterised by sudden death, peracute septicaemia, bleeding from orifices and subcutaneous haemorrhages. Other clinical signs including the following have been described:
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[[Category:To_Do_-_SophieIgnarski]]
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* Acute onset severe pyrexia
 
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* Depression
 
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* Neurological signs such as staggering or trembling
 
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* Cyanosis
 
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* Dyspnoea
 
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* Cessation of rumination
 
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* Subcutaneous oedematous swellings
 
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* Congested mucous membranes and petechiae
 
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* Shivering and cramp-like clinical signs
 
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===Pigs===
 
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Pigs are relatively resistant to anthrax. The disease in pigs has two manifestations; a pharyngeal and an intestinal form.
 
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The '''pharyngeal''' disease is linked with scavenging or purposeful feeding of infected carcasses and often begins as an oedematous cellulitis of the the neck, head and regional lymph nodes. This may cause death by asphyxia.
 
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The '''intestinal''' form is thought to be associated with contaminated mineral supplements, and may produce less obvious clinical signs including diarrhoea, lethargy and anorexia. Animals affected by the intestinal form frequently recover.
 
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===Dogs===
 
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Dogs are rarely affected, but develop a similar disease to that found in pigs. Disease most often occurs due to scavenging of infected sheep or cattle carcasses. Clinical signs include severe inflammation and oedema of the pharyngeal region and the disease is usually not fatal.
 
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==Diagnosis==
 
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Diagnosis is confirmed in most affected animals (other than pigs) by demonstration of large numbers of rod-shaped ''B. anthracis'' in the blood or tissue. A tissue sample from a fresh carcass may be collected from an incision made in a well vascularised area such as the ear. As pigs with localised disease are rarely bacteraemic, a small piece of lymphatic tissue should be collected aseptically and submitted. Diagnostic tests include '''bacterial culture, PCR''' and '''fluorescent antibody stains''' for demonstration of the bacillus in blood or tissue.
 
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===Pathology===
 
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Bloody discharges from body orifices may be observed in carcasses and ''rigor mortis'' is often absent or incomplete in dead animals. Failure of the blood to clot and splenomegaly are other important ''post mortem'' findings. Lymph nodes are often swollen and oedematous. Haemorrhages may be found on the serosal surfaces of the thorax and abdomen as well as the endocardium.
 
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==Treatment==
 
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'''Penicillin''' and '''Streptomycin''' is the treatment of choice in animals suspected to be suffering from Anthrax. All livestock at risk from infection should be treated with a long-acting antibiotic and moved to uncontaminated pasture. Any suspected contaminated feed should be removed. 
 
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==Control==
 
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Animals in endemic areas should be vaccinated on an annual basis with the '''non-encapsulated Sterne strain vaccine'''. As the vaccine is live, antibiotics should not be administered within one week of vaccination.
 
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{{Learning
 
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|literature review = [http://www.cabdirect.org/search.html?rowId=1&options1=AND&q1=%28%28title%3A%28anthracosis%29%29%29+OR+%28%28title%3A%28Anthrax%29%29%29&occuring1=freetext&rowId=2&options2=AND&q2=&occuring2=freetext&rowId=3&options3=AND&q3=&occuring3=freetext&publishedstart=2000&publishedend=yyyy&calendarInput=yyyy-mm-dd&la=any&it=any&show=all&x=47&y=9 Anthrax publications since 2000]
 
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|full text = [http://www.cabi.org/cabdirect/FullTextPDF/2007/20073085070.pdf ''' Anthrax - the forgotten plague.''' Clark, C.; Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada, Large Animal Veterinary Rounds, 2006, 6, 10, pp 1-6, 11 ref]
 
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}}
 
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==References==
 
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* Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''' ''Merial''
 
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* Turnbull, P (2007) '''Anthrax in Humans and Animals (Fourth Edition)''' ''World Health Organisation Press''
 
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* Jones, T. C., Hunt, R. D., King, N. W. (1997) '''Veterinary Pathology''' ''Wiley-Blackwell''
 
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{{review}}
 
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{{OpenPages}}
 
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[[Category:Alimentary Diseases - Cattle]][[Category:Alimentary Diseases - Pig]][[Category:Alimentary Diseases - Dog]][[Category:Lymphoreticular and Haematopoietic Diseases - Dog]]
 
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[[Category:Alimentary Diseases - Horse]][[Category:Neurological Diseases - Horse]][[Category:Respiratory Diseases - Horse]]
 
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[[Category:Alimentary Diseases - Sheep]][[Category:Neurological Diseases - Sheep]][[Category:Respiratory Diseases - Sheep]]
 
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[[Category:Brian Aldridge reviewing]]
 
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[[Category:Spleen - Pathology]]
 

Revision as of 19:27, 27 July 2010


 This article is still under construction.



Description

Anthrax is a zoonotic disease caused by the spore-forming bacterium Bacillus anthracis.

  • Clinical signs:
    • Cattle/sheep:
      • Fatal peracute septicaemia
      • Animals usually found dead
      • Pyrexia, depression, congested mucous membranes and petechiae before death
      • Abortion, subcutaneous oedema and dysentry in animals surviving more that one day
    • Pigs:
      • Subacute anthrax with oedematous swelling of throat, head and regional lymph nodes
      • Intestinal form with high mortality - dysentry due to haemorrhagic enteric lesions
      • Peritonitis
    • Horses:
      • Subacute anthrax with subcutaneous oedema of thorax, abdomen and legs following entrance of spores into abrasions
      • Septicaemia with colic and dysentry due to haemorrhagic enteritis from ingestion of spores; ecchymoses and splenomegaly
    • Dogs
      • Rarely affected, but similar disease to that found in pigs
    • Humans
      • Cutaneous anthrax - localised lesion from entrance into abrasion which can cause septicaemia
      • Pulmonary anthrax - inhalation of spores
      • Intestinal anthrax - ingestion of infective material
  • Diagnosis:
    • Post mortem: bloat, incomplete rigor mortis, ecchymoses, oedema, dark unclotted blood from orifices, blooy fluid in body cavities, splenomegaly
    • Blood smear from an ear or tail vein of ruminants, or peritoneal fluid from pigs stained with polychrome methylene blue
    • Chains of square-ended blue rods surrounded by mauve capsules
    • Culture on blood and MacConkey agar (no growth on MacConkey)
    • Biochemical tests
  • Treatment:
    • High doses of penicillin G or oxytetracylcine
  • Control:
    • Report suspected cases - notifiable
    • Spores destroyed by sterilisation
    • Endemic regions:
      • Live Sterne spore vaccine which produces toxin but has no capsule, therefore is non-pathogenic; stimulates protective antibody
      • Chemoprophylaxis with long-acting penicillin
    • Non-endemic regions after an outbreak:
      • Movement restrictions
      • Footbath with sporicidal disinfectant
      • Fumigate buildings with formaldehyde
      • Dispose carcases and contaminated material
      • Isolate in-contact animals
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