by Alison Bowler

Created on: April 24, 2010

Anthrax is a disease of animals, which can also infect man. The bacterium causing anthrax, Bacillus anthracis, is a gram-positive aerobic spore-bearing bacillus. Most human infections arise after contact with infected animal products such as hides, meat, fur or wool. Some cases develop from close contact with contaminated pastures. Cases of deliberate infection with the bacterium as an agent of biological warfare also occur. There are three types of recognized anthrax infection cutaneous, pulmonary and gastrointestinal.

Cutaneous anthrax is the most common and least severe form of the infection. The bacteria enter the skin via a cut or abrasion. The site of infection starts to itch before a red-brown spot appears on the skin surface. This enlarges and hardens. The center of the spot blisters then ulcerates before forming a black crust or eschar. Lymph nodes close to the site of infection enlarge. Symptoms associated with cutaneous anthrax include painful muscle aches, headache, fever, nausea and vomiting. This form of anthrax responds readily to antibiotic therapy. Occasionally the bacteria in untreated cases spread to the blood to cause a fatal septicemia.

Pulmonary anthrax also known as inhalation anthrax or wool sorter's disease starts with the inhalation of anthrax spores. An early sign of infection is the gradual onset of a flu-like illness. Within a few days the condition of the patient worsens as they develop severe respiratory distress. They then go into shock and coma before dying. Even when treated with antibiotics this form of anthrax is frequently fatal. It is this form of anthrax that the weaponized anthrax causes when used as an agent of biological warfare.

When a person inhales anthrax spores their macrophages engulf the spores and carry them to the lymph nodes. While some spores do not survive some develop into vegetative bacteria and multiply in the lymph nodes.  The growing bacteria produce toxins which causes hemorrhage and necrosis (tissue death) of the lymph nodes. The bacteria spread back to the lungs where they continue to produce their deadly toxins. Antibiotics may kill the bacteria but the toxins remain within the body and continue to damage to the lungs.

The final form of anthrax is the rarest. Gastrointestinal anthrax occurs after the ingestion of undercooked or raw meat from an infected animal. Infection of the intestinal tract causes fever, loss of appetite, abdominal pain, nausea and bloody diarrhea. Damage to the bowel wall allows the anthrax bacteria to enter the bloodstream to cause a fatal toxic septicemia. Early treatment prevents some fatalities, but even treated gastrointestinal anthrax may have a mortality rate of 20-80%.

If you suspect you have been in contact with anthrax do not wait for the start of symptoms. Contact a qualified medical practitioner to arrange prophylactic antibiotic treatment.

Reference sources:
HPA UK Health Protection Agency
CDC Centers for Disease Control and Prevention
Medline Plus US National Library of Medicine

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