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Anthrax (Evaluation of suspected cutaneous anthrax cases and specimen collection procedures)

Cutaneous anthrax

Cutaneous anthrax follows deposition of the organism onto a cut, sore or abrasion on the skin, occurring particularly on exposed areas of the hands, arms, or face. An area of local edema becomes a pruritic macule or papule, which enlarges and ulcerates after 1-2 days. Small, 1-3 mm vesicles may surround the ulcer. The vesicles may become hemorrhagic, with satellite vesicles. A painless, depressed, black eschar (necrotic ulcer) forms in 3-7 days. The tissue surrounding the skin lesion is often erythematous, and may have varying degrees of edema (brawny, gelatinous, non-pitting edema). Patients may have fever, malaise, headache and regional lymphadenopathy. The case fatality rate for cutaneous anthrax is 20% without and < 1% with antibiotic treatment. Cutaneous anthrax is not easily transmissible from person to person, although there is a very low risk of infection if there is direct contact with the drainage from an open sore. The incubation period is usually from 1-7 days, but may range up to 12 days.

Report patients meeting the following criteria for suspected cutaneous anthrax:

  1. Any person with highly characteristic skin lesion and typical progression:

    1. An ulcerative lesion with surrounding erythema, edema, or vesicles

    2. A blackened eschar forming 3 to 7 days after onset of skin lesion

    Any person with a less characteristic skin lesion:

    1. An ulcerative or necrotic lesion

    2. A risk exposure history. Some examples of suspicious exposures at the current time are:

      1.     Occupational: Any of the following occupational exposures, particularly if the person handles mail: (a) a person who works in a media outlet, (b) a postal worker, or (c) a person who works in a high-profile setting (e.g., government agency, large corporation, public institution or religious organization).

      2.     Credible threat exposure: A history of exposure to a suspicious powder or object that has been evaluated by law enforcement and is considered a credible threat.


    1. Laboratory evidence suggestive of possible B. anthracis infection.
      Examples include:

      1.     Gram stain showing Gram-positive bacilli from a skin lesion, sterile fluid, or tissue

      2.     Culture showing encapsulated non-motile non-hemolytic bacilli from any body fluid or site

      Instructions for Collecting Laboratory Diagnostic Specimens for Suspected Cutaneous Anthrax

      If you have a case that meets the above criteria, please contact Orange County Public Health (OCPH) immediately (see below). Be sure to take appropriate infection control precautions to avoid contact with specimens.

      Send the following specimens to your routine microbiology laboratory

      1.     Culture and gram stain of skin lesion:

      1.     Synthetic (non-cotton) swab with non-wooden stick for culture and gram stain of material swabbed from the exudate or the most actively inflamed area of the eschar

      2.     If suspicious Bacillus species* is identified, contact OCPH immediately.

      If the patient is febrile or hospitalized, or meets criteria in A above:

      1.     Blood culture:

      Send to routine hospital laboratory, if suspicious Bacillus species* is identified, contact OCPH immediately

      OCPH may request or arrange for the following specimens to be sent to a Public Health Lab

      1.     Skin (punch) biopsy:

      1.     Consider if patient is on antimicrobial drugs OR if gram stain and culture are negative for B. anthracis and clinical suspicion remains high.

      2.     One biopsy specimen in formalin, keep at room temperature, for possible histopathology and immunohistochemical staining. Paraffin-embedded specimens are acceptable as well.

      1.     Acute serum for possible ELISA testing for B. anthracis at CDC: Ideally, within 5 days of illness onset,

      1.     Collect ~5 ml of whole blood in a serum separator tube, refrigerate or keep at room air

      2.     Spin down as soon as possible

      3.     After spinning, separate serum and freeze the tube of serum at -70 C or place on dry ice

      1.     Convalescent serum for ELISA testing for B. anthracis at CDC: 14-21 days after acute sera,

      1.     Collect ~5 ml of whole blood in a serum separator tube, refrigerate or keep at room air

      2.     Spin down as soon as possible

      3.     After spinning, separate serum and freeze the tube of serum at -70 C or place on dry ice.

      1.     Whole blood for PCR: EDTA-containing tube (purple top)

      *Suspicious Bacillus species: Large, Gram-positive rods with spores; non-motile and non-hemolytic Bacillus species on preliminary culture.

      Please be sure to completely and clearly label all specimens with the following information:


      •     DATE OF BIRTH




      Call the Orange County Public Health/Epidemiology program immediately:

      During business hours, please call (714) 834-8180.
      After business hours, call Sheriff Communications at (714) 628-7008 and ask to speak to the Public Health Official on call.

      Please have the following information available:

      •     Patient name

      •     Patient contact information

      •     Medical history

      •     Illness onset date

      •        Characteristics and progression of skin lesion

      •        Presence of systemic symptoms

      •       Treatment history

      •        Laboratory and radiologic data

      •        Detailed exposure and employment history

      This information will be used to help determine the patient's risk for anthrax infection. When you call to report a case, we will help to determine whether further testing is necessary.

      For more information see Morbidity and Mortality Weekly Report (MMWR) from CDC, October 26 and November 1, 2001:

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      Adapted from: The New York City Department of Health and the Los Angeles County Department of Health Services, Acute Communicable Disease Control and CDC (MMWR 11-2-01)

      Adapted from materials developed by the Washington State Department of Health, New York City Department of Health, the California Department of Health Services, and the Centers for Disease Control and Prevention. Reuse or reproduction of this material is authorized.