This condition is usually acquired through contact with infected livestock or animal products such as wool or bristles.
Previously rare in industrialized countries, its importance has increased there since the recent wave of bio-terrorist attacks. The spores of Bacillusanthracis, the causative organism, are highly resistantto physical and chemical agents.
Anthrax has two main clinical variants: inhalational anthrax, which is outside the scope of this book; and cutaneous anthrax. The incubation period of the latter is usually between 2 and 5 days. A skin lesion then appears on an exposed part, often in association with a variable degree of cutaneous oedema, which can sometimes be massive, especially on the face. Within a day or two, the original small painless papule shows vesicles that quickly coalesce into a larger single blister. This ruptures to form an ulcer with a central dark eschar, which falls off after 1–2 weeks leaving a scar. The skin lesions are often accompanied by fever, headache, myalgia and regional lymphadenopathy. The mortality rate for untreated cutaneous anthrax is up to 20%; with appropriate antibiotic treatment, this falls to less than 1%.
Cultures of material taken from the vesicle may be positive in 12– 48 h; a Gram stain will show Gram-positive bacilli, occurring singly or in short chains. Quicker results may be obtained by a direct fluorescent antibody test, or by an enzyme-linked immuno-absorbant assay (ELISA)aboth of which are currently available only at reference laboratories. Before the results are available, it is wise to assume that the organism is penicillin- and tetracycline-resistant, and to start treatment with ciprofloxacin at 400 mg intra-venously every 12 h or, for milder cases, ciprofloxacin 50 mg orally every 12 h. The latter dose is suitable for prophylactic use in those who are known to have been exposed to spores. A switch to an alternative regimen can be made once the antibiotic sensitivity of the organ-ism has been established. At present, anthrax vaccine is in short supply; it requires six injections over 18 months, with subsequent boosters, to prevent anthrax.
Skin lesions are important clues to the diagnosis of this condition, in which the symptoms and signs of classical gonorrhoea are usually absent. The patient, usually a woman with recurring fever and joint pains, develops sparse crops of skin lesions, usually around the hands and feet. The grey, often haemorrhagic, vesicopustules are characteristic. Rather similar lesions are seen in chronic meningococcal septicaemia.