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anthrax

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References:

  1. Global Infectious Diseases and Epidemiology Online Network: Infectious Diseases of the Philippines, 2013 eBook Edition, ISBN 978-1-61755-582-4, by Stephen Berger. Accessed here.
AgentBACTERIUM. Bacillus anthracis An aerobic gram positive bacillus
ReservoirSoil
Goat
Cattle
Sheep
Water
Horse
VectorFly (rare)
VehicleHair
Wool
Hides
Bone products
Air
Meat
Incubation Period1 to 7 days; 1 to 12 days if cutaneous, 1 to 7 days if gastrointestinal, 1 to 43 days if pulmonary
Diagnostic TestsBacteriological culture. Alert laboratory that organism may be present. Serology and rapid tests by Ref. Centers.
Typical Adult TherapyIsolation (secretions). Ciprofloxacin; alt. Doxycycline, Penicillin G. Add Clindamycin + Rifampin for pulmonary infection. Dosage/route/duration as per severity
Typical Pediatric TherapyIsolation (secretions). Ciprofloxacin ( Doxycycline if age >= 8y ). Add Clindamycin + Rifampin for pulmonary infection. Dosage/route/duration as per severity
VaccineAnthrax
Clinical HintsEdematous skin ulcer covered by black eschar - satellite vesicles may be present; fulminant
gastroenteritis or pneumonia; necrotizing stomatitis; hemorrhagic meningitis. Acquired from contact with large mammals or their products (meat, wool, hides, bone).
SynonymsAntrace, Antrax, Antraz, Carbunco, Carbunculo, Malcharbon, Malignant pustule, Miltbrann, Miltvuur, Milzbrand, Mjaltbrand, Siberian plague, Siberian ulcer, Splenic fever, Wool-sorter’s disease.

CDC Case Definition for Reporting

As of 1996, the CDC (The United States Centers for Disease Control) case definition for reporting purposes consists of any illness with acute onset characterized by one or more of the following:

  1. Cutaneous (a skin lesion evolving during a period of 2-6 days from a papule, through a vesicle to a depressed black eschar)
  2. Pulmonary (hypoxia, dyspnea and mediastinal widening following a brief ‘viral-type’ prodrome)
  3. Intestinal (severe abdominal distress followed by fever or signs of septicemia)
  4. Oropharyngeal (mucosal lesion, cervical adenopathy and edema, and fever)
  5. Demonstration of Bacillus anthracis by culture, immunofluorescence or serological response.

WHO Case Definition for Surveillance

An illness with acute onset characterized by several clinical forms. These are:

  1. Localized Form:
    • Cutaneous: skin lesion evolving over 1 to 6 days from a papular through a vesicular stage, to a depressed black eschar invariably accompanied by edema that may be mild to extensive
  2. Systemic forms:
    • Gastro-intestinal: abdominal distress characterized by nausea, vomiting, anorexia and followed by fever
    • Pulmonary (inhalation): brief prodrome resembling acute viral respiratory illness, followed by rapid onset of hypoxia, dyspnea and high temperature, with X-ray evidence of mediastinal widening
    • Meningeal: acute onset of high fever possibly with convulsions, loss of consciousness, meningeal signs and symptoms; commonly noted in all systemic infections

Laboratory criteria for diagnosis

  • Isolation of Bacillus anthracis from a clinical specimen (e.g., blood, lesions, discharges)
  • Demonstration of B. anthracis in a clinical specimen by microscopic examination of stained smears (vesicular fluid, blood, cerebrospinal fluid, pleural fluid, stools)
  • Positive serology (ELISA, Western blot, toxin detection, chromatographic assay, fluorescent antibody test (FAT)
  • Note: It may not be possible to demonstrate B. anthracis in clinical specimens if the patient has been treated with antimicrobial agents.

Case classification

  1. Suspected: A case that is compatible with the clinical description and has an epidemiological link to confirmed or suspected animal cases or contaminated animal products.
  2. Probable: A suspected case that has a positive reaction to allergic skin test (in non-vaccinated individuals).
  3. Confirmed: A suspected case that is laboratory-confirmed.

Cutaneous Anthrax

  • 95% of anthrax cases (worldwide) are cutaneous.
  • The incubation period for cutaneous anthrax ranges from 12 hours to 12 days.
  • Cutaneous anthrax begins with pruritus at the affected site, typically followed by a small, painless papule that progresses to a vesicle in 1 to 2 days.
  • The lesion erodes, leaving a necrotic ulcer with a characteristic black center.
  • Secondary vesicles are sometimes observed.
  • Lymphadenopathy may occur, and local edema may be extensive.
  • Patients may have fever, malaise, and headache.
  • The most common sites of cutaneous anthrax are the hands, forearms, and head.
  • Anthrax related to illicit drug injection may present as subcutaneous infection rather than overt skin lesions.
  • Rarely infection may involve the genital area, eyelid or other areas.
  • Cutaneous anthrax is fatal in approximately 20% of cases if left untreated.

Inhalational Anthrax

  • Infection may progress to respiratory failure and shock within 1 to 2 days following onset of symptoms.
  • The case-fatality rate exceeds 80%, even with appropriate antibiotic therapy.
  • Symptoms include pharyngeal pain, cough, fever and myalgia followed by respiratory distress, cervical edema and venous engorgement suggestive of mediastinitis.

Gastrointestinal Anthrax

  • Infection is characterized by pharyngeal pain, nausea, vomiting, and bloody diarrhea.
  • Intestinal gangrene, obstruction and perforation may ensue.
  • The case-fatality rate for intestinal infection ranges from 25% to 60%.
  • Ulcerative lesions, usually multiple and superficial, may occur in the stomach, sometimes in association with similar lesions of the esophagus and jejunum.
  • Ulcers may bleed, and in severe cases the hemorrhage may be massive and fatal.
  • Ascites may be present.
  • Lesions in the mid-jejunum, terminal ileum, or cecum tend to develop around a single site or a few sites of ulceration and edema, similar to cutaneous anthrax.

Oropharyngeal Anthrax

  • Infection is characterized by painful neck swelling and fever.
  • The other common symptoms are sore throat, dysphagia, and hoarseness, enlargement of cervical lymph nodes and soft tissue edema.
  • Oral lesions are located on the tonsils, posterior pharyngeal wall, or the hard palate.
  • In severe cases, the tonsillar lesions extended to involve the anterior and posterior pillars of fauces, as well as the soft palate and uvula.
  • Early lesions are edematous and congested.
  • By the end of the first week, central necrosis and ulceration produce a whitish patch, which evolves to a pseudomembrane which covers the ulcer after an additional week.

Meningeal Anthrax

  • Infection is characterized by fever, malaise, meningeal signs, hyperreflexia, and delirium, stupor, or coma.
  • CSF analyses demonstrated hemorrhagic meningitis, with positive Gram’s stains and CSF cultures.
  • 75% of patients die within 24 hours of presentation; mortality rates of 100% are reported in some series.
  • Pathologic findings include hemorrhagic meningitis, multifocal subarachnoid and intraparenchymal hemorrhages, vasculitis, and cerebral edema.

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