Cause
The cause of anthrax is a gram-positive bacterium called Bacillus anthracis. These bacteria form spores when exposed to the air and the spores can survive for a long time in the environment - spores have been recorded to survive as long as 60 years . These spores are resistant to changes in environmental temperatures, common disinfectants and processing of meat and by-products such as curing hides or rendering to produce bone meal. Spores survive especially well in warm conditions, alkaline, poorly drained soil and in the presence of organic material.

Outbreaks of the disease occur when environmental temperatures exceed 15⁰ C. 

The bacteria produce a deadly toxin which causes death by causing shock and acute renal failure.

If an infected animal is allowed to decompose the bacteria are destroyed, but opening the carcase exposes the bacteria to air, and results in spore formation and contamination of the soil, and an exposure risk for humans. For this reason post-mortem examination of suspect animals is not recommended.

Animals become infected from soil by spores entering:

• Cuts - inside the mouth, or in the skin - common route of infection
• By ingestion of contaminated soil/food or water. Common route of infection  - eg ingestion of contaminated bone meal.
• By inhalation of spores -"Woolsorters disease" in humans is due to the inhalation of spores in wool workers.
• Transmission from biting insects - possible source
• Following vaccination against anthrax - if the spores have not been killed adequately

• Agricultural workers
• Animal handlers
• Butchers
• Weavers
• Wool sorters
• Veterinarians

Signs usually occur 1-2 weeks after exposure to the spores. The disease is almost always fatal  in domestic animals except in pigs. . Signs that are seen include :

• Cats
  • Anthrax is uncommon in cats.
  • Infection occurs following ingestion of infected meat or bone meal.
  • Swellings of the head and neck - can cause asphyxiation
  • Acute, fatal gastroenteritis
• Cattle and Sheep
  • Sudden death
  • Fever (up to 42⁰ C)
  • Muscle tremors
  • Difficulty breathing and increased breathing rate
  • Collapse
  • Exposed mucous membranes look dark in colour and congested
  • Increased heart rate
  • Anorexia
  • Depression
  • Abortion in pregnant cattle
  • Diarrhoea and dysentery
  • Swellings in the throat
  • Swelling (oedema) of the sternum flanks and perineal region may occur. 
  • Milk changes colour - yellow or blood-stained
  • After death blood does not clot may discharge out of the nose, mouth and other orifices.
• Dogs
  • Anthrax is uncommon in dogs.
  • Infection occurs following ingestion of infected meat or bone meal.
  • Swellings of the head and neck - can cause asphyxiation
  • Acute, fatal gastroenteritis
• Horses and Ponies
  • Abdominal pain (colic) following ingestion
  • Fever 
  • Depression
  • Swellings due to oedema - following insect bite - throat, and lower parts of the body including the  neck, underside of chest and abdomen.
  • Death in 2-8 days
• Humans (Woolsorter's or Ragpicker's Disease)
  • Localised, black skin reaction with cutaneous papules and ulcers- most common 
  • Fever
  • Lymphadenopathy
  • Myalgia
  • Upper respiratory signs
  • Pneumonia
  • Septicaemia can occur which is fatal.
• Pigs
  • Swelling of the throat and face
  • Anorexia
  • Depression
  • Blotchy red-purple haemorrhages appear in the skin
  • Dysentery may occur
  • Pneumonia and pleurisy- in young pigs following inhalation of spores.
  • Death - up to 3 days after signs appear

Complications
The Bacillus anthracis spores can survive for very long periods in soil, which can present a problem of infected land.

• Formalin (10%)
• Sodium hydroxide (5-10%)
• Ethylene oxide for shoes - for 18 hours

Vaccines are available against anthrax for use in countries in which the disease is endemic and where vaccination is allowed. Vaccination is not allowed in the UK.