Anthrax

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This is a highly infectious disease of animals especially ruminants, transmitted to man by contact with the animal or animal products (carcasses) or faeces. The causative organism, Bacillus anthracis is a large gram-positive, facultatively anaerobic, encapsulated rod. The spores are resistant to destruction, remaining viable in soil and animal products for decades.

Human infection is usually through the skin but has occurred following ingestion of contaminated meat. Inhalation of spores under adverse conditions (e.g. the presence of acute respiratory infection) may result in pulmonary anthrax (wool sorter’s disease) which is often fatal.

Clinical Features

The occupational history of the patient is often important. The incubation period varies from 12 hours to 5 days.

The cutaneous form: begins as a red-brown papule that enlarges with considerable peripheral erythema, vesiculation, and induration. Central ulceration follows, with serosanguineous exudation and formation of a black eschar. Local lymphadenopathy may be seen; occasionally fever, malaise, nausea, vomiting, myalgia and headache.

Pulmonary Anthrax: This follows the rapid multiplication of spores in the mediastinal structures. Serosanguineous transudation, pulmonary oedema, and pleural effusion occur. Initial symptoms are insidious and resemble influenza. Fever increases, within a few days and severe respiratory distress, develop. Chest x-ray may show diffuse patchy infiltration; the mediastinum is widened because of enlarged haemorrhagic lymph nodes.

Treatment

Treatment is mainly by an antibiotic, penicillin is the antibiotic of choice:

  • Procaine penicillin-G 600,000 unit I.M twice daily for 7 days prevents the systematic spread and induces gradual resolution of the pustule

OR

  • Tetracycline 2g per day in 4 divided doses for seven days

OR

  • Erythromycin at 500mg 6 hourly is a good alternative in children or pregnancy for seven days.

For pulmonary anthrax: Early and continuous I.V. therapy of Benzylpenicillin 20MU per day may be life-saving.

If treatment is delayed (usually because the diagnosis is missed), death is likely to occur.

Prevention

A vaccine is available for those at high risk (veterinarians, laboratory technicians, butchers and employees of textile mills processing goat hair); advocating the use of personal protective equipment, gloves, overalls, boots should be encouraged.