ANTHRAX

Infectious agent:

Bacillus anthracis, a gram-positive, encapsulated, sporeforming rod. This zoonotic disease can manifest in 3 forms - cutaneous, gastrointestinal, inhalational.

Incubation:

1-7 days, although incubation periods up to 60 days are possible.

Mode of transmission:

Cutaneous anthrax --contact with infected tissues or hair of animals (cattle, sheep, pigs, horses); contact with soil associated with infected animals or contaminated bone meal used in gardening.

Gastrointestinal anthrax from ingestion of contaminated undercooked meats

Inhalational anthrax --aerosolized spores inhaled during risky industrial processes (tanning hides, processing wool or bone) or biowarfare.

Transmission person to person is unlikely.

Period of communicability:

Articles and soil contaminated with spores may remain infective for decades.

Prophylaxis if exposed:

Ciprofloxacin 500 mg BID or doxycycline 100 mg BID up to 60 days.

Clinical Symptoms

Inhalational form of the disease is of most concern in bioterrorist attacks since the spores can be delivered by aerosol route.

Two-stage illness: nonspecific flu-like illness followed by rapid deterioration to acute respiratory distress, sepsis, meningitis and/or hemorrhagic mediastinitis.

STAGE 1: Nonspecific flu-like illness (fever, malaise, fatigue), with possible mild cough or chest pain, headache, vomiting, chills, weakness, abdominal pain. This stage lasts from hours to a few days. After a brief period of apparent recovery, some patients progress to next stage.

STAGE 2: Sudden onset of respiratory distress with dyspnea, diaphoresis, stridor, fever, cyanosis and shock. Chest X-ray findings of mediastinal widening (due to massive lymphadenopathy, causing stridor) in a previously well patient with evidence of overwhelming flu-like illness is pathognomonic of advanced inhalational anthrax. Up to half of patients develop hemorrhagic meningitis with concomitant meningismus, delirium, and obtundation. Death follows in 24-36 hours. Inhalation anthrax has resulted in fatality rates of 86% or more in the past.

Diagnosis:

Culture from blood, skin lesions, respiratory secretions or serology. PCR has been also used in the US.

Source:

Control of Communicable Diseases Manual, Chin 17^th edition, 2000