MM 209-210; ID 1003-1008

NAMES OF DISEASE:         Anthrax
                                                     Black bane
                                                     Malignant pustule
 

OVERVIEW:

The spores of Bacillus anthracis are commonly found on animal pelts. When the spore is deposited on an open wound, it germinates and produces a dermatotoxin which causes the formation of a malignant pustule with a black eschar.
 

ETIOLOGICAL AGENT:

Bacillus anthracis. This is a Gram⁺ sporeforming rod that grows aerobically. It is non-motile and encapsulated. The capsule is made of polyglutamic acid.
 

PATHOLOGY:

The virulence of B. anthracis is directly related to the presence of a capsule (D-glutamic acid). Even avirulent strains produce an exotoxin. The toxin is comprised of three distinct, antigenically active components. All are thermolabile proteins or lipoproteins:

            Factor I (Edema factor) - necessary for the edema-producing activity of the toxin

            Factor II (Protective antigen) - induces protective antibodies

            Factor III (Lethal factor) - essential for lethal effect

    Edema factor plus protective antigen = edema

    Lethal factor plus protective antigen = death
 

SYMPTOMOLOGY:

The primary lesion usually develops at the site of a minor scratch or abrasion in an exposed area of the face, neck or upper extremities after an incubation period of 1-7 days. It begins as a small, inflamed papule which later becomes vesicular. Eventually the vesicle breaks down and is replaced by a black eschar. A striking "gelatinous" non-pitting edema surrounds the eschar for a considerable distance. At no stage is the lesion particularly painful. In severe cases of cutaneous anthrax the regional lymph nodes become enlarged and tender and the blood stream is eventually invaded.

DIAGNOSIS:

Cutaneous anthrax should be considered whenever a painless, pruritic papule on an exposed part of the body progresses through a vesicular stage to become a black, depressed eschar, regardless of antimicrobial therapy. The recovery of B. anthracis from vesicular fluid or exudate from the ulcer confirms the diagnosis. A differential diagnosis should include:

1. Anthrax

2. Staphylococcal skin lesions - more pyogenic, spread more rapidly, usually multiple lesions. Painful, only small black
    eschar.

3. Tularemia - the most common type is ulceroglandular. The skin is ulcerated at the point of entry and the regional lymph
    nodes become enlarged. This can be differentially diagnosed by serological techniques or isolation of the organism.
    Etiological agent is gram negative (Francisella tularensis).

4. Plague. Symptoms are similar to tularemia. Etiological agent is gram negative. (Yersinia pestis).

5. Milker's nodules. These occur only on the hands and do not generally form an eschar.

6. Orf. Generally occurs on the fingers. The orf virus is a poxvirus which shows characteristic pathology (tube-like
    intracytoplasmic inclusion bodies).
 

TREATMENT:     Penicillin G
                                  Ciprofloxacin
                                  Doxycycline
 

PREVENTION:

In the past there was a vaccine available for those with occupational exposure to anthrax. More recently the U.S. military has signed an agreement with the sole producer of the vaccine for exclusive use of the vaccine. If the military vaccine is the same as the vaccine previously used to prevent occupational anthrax then it is an alum precipitate of the protective antigen. There is some speculation that the military has added the lethal factor and the edema factor to the preparation. The military schedule calls for 3 injections, 2 weeks apart followed by injections at 6, 12 and 18 months with an annual booster.