Overview
Causative Agent
- Bacillus anthracis
- Aerobic, gram-positive, rod-shaped, encapsulated and spore-forming bacterium
Incubation Period
- 1 - 6 days (up to 30 days)
Infectious Period
- Articles and soil contaminated with spores can remain infective for decades.
Transmission
- A zoonotic disease mainly of herbivorous animals; transmitted by direct contact with B. anthracis-infected animal tissues or products from infected animals i.e. drums, or with anthrax spores in soil. Humans are generally incidental hosts.
- Anthrax in human is not considered contagious; person-to person transmission of cutaneous anthrax has rarely been reported.
Three forms exist:
- Cutaneous anthrax: As a result introduction of the spore through the skin (especially via abrasions).
- Gastrointestinal anthrax: As a result of ingestion of infected tissues.
- Inhalation anthrax: As a result of inhaling spores aerosolized by industrial processing of contaminated materials i.e. hides, among persons working with contaminated animal skin or bioterrorism.
Epidemiology
- Most common in agricultural regions in Central and South America, sub-Saharan Africa, Central and Southwestern Asia and Southern and Eastern Europe.
Three main forms of disease:
- Cutaneous: Usually manifests as a black, necrotic skin lesion.
- Gastrointestinal: Rare, but highly fatal form that occurs after ingestion of contaminated meat.
- Inhalational: Most lethal form (mortality > 80%) that occurs following inhalation of spores.
Cutaneous anthrax:
- Case fatality
Detection & Treatment
- Suitable specimens as indicated include blood cultures, cerebrospinal fluid, sputum, lymph node biopsy, peritoneal fluid, stool or rectal swab for gastrointestinal anthrax, and sub-eschar material and vesicular fluid for cutaneous anthrax. Please contact the laboratory in advance to discuss the most appropriate workup.
- Nasal swabs are only for supporting a confirmed exposure to B. anthracis or epidemiological studies and are not recommended for routine investigation without specific advice from MOH.
- Gram stain may show typical Gram-positive bacilli occurring singly or in short chains often with squared off ends (safety-pin appearance).
- CXR: widened mediastinum without infiltrates in previously healthy patient in the absence of trauma is pathognomonic for anthrax.
- PCR-contact MOH
- Environmental testing-contact MOH
Care Management
Treatment should be initiated as soon as diagnosis is suspected. Antibiotic administration at the earliest signs of disease is essential. Ciprofloxacin or doxycycline should be considered an essential part of first-line therapy for inhalational anthrax. Combination antimicrobial therapy is recommended for inhalational anthrax infection.
Adults:
- IV ciprofloxacin 400 mg 12 hourly empirically or
- IV doxycycline 100 mg 12 hourly (if available) plus
- One or two additional agents: rifampicin, vancomycin, chloramphenicol, imipenem, clindamycin or clarithromycin.
All patients should be given the anthrax vaccine if available. Antibiotic treatment should be continued until three doses of vaccine have been administered (day 0, 14 and 28). If vaccine is unavailable, antibiotic treatment should be continued for 60 days.
Children:
- IV ciprofloxacin 20-30 mg/kg/day bd (not to exceed 1g/day) or
- IV doxycycline 2.2 mg/kg 12 hourly for patients
Specialties & Services
