Anthrax

Anthrax

There are three recognized forms of infection with Bacillus anthracis:

1.      Cutaneous anthrax.

2.     Gastrointestinal anthrax.

3.     Inhalational (pulmonary) anthrax.

Cutaneous Anthrax

The skin lesion is associated with occupational exposure to anthrax spores during processing of hides and bone products, or with bioterrorism. It accounts for the vast majority of clinical cases. Animal infection is a serious problem in Africa, India, Pakistan and Middle East.

Spores are inoculated into exposed skin.

A single lesion develops as an irritable papule on an oedematous haemorrhagic base. This progresses to a depressed black eschar.

Despite extensive oedema, pain is infrequent.

Gastrointestinal anthrax

This is associated with the ingestion of meat products that have been contaminated or incompletely cooked. The caecum is the seat of the infection, which produces nausea, vomiting, anorexia and fever. Followed in 2-3 days by severe abdominal pain and bloody diarrhea. Toxaemia and death can develop rapidly thereafter.

Inhalational anthrax

This form of the disease is extremely rare unless associated with bioterrorism. Without rapid and aggressive therapy at the onset of symptoms, the mortality is greater than 90%. Fever, dyspnea, cough, headache and symptoms of septicaemia develop 3-14 days following exposure. Typically, there is little on the chest X-ray other than widening of the mediastinum and pleural effusion.

Management

B. Anthracis can be cultured from lesional skin swabs. Skin lesions are readily curable with early antibiotic therapy. Treatment is with ciprofloxacin 500mg daily until penicillin susceptibility is confirmed; the regimen can then be changed to benzylpenicillin 600 000 units i. m. 6 hourly or phenoxymethylpenicillin 500mg 6 hourly. Aggressive fluid resuscitation and the addition of an aminoglycoside may improve the outlook. Ventilatory assistance will be required.

Prophylaxis with ciprofloxacin 500mg 12 hourly for high risk of exposure to biological warfare.