Anthrax
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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
- Cattle/sheep:
- 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