Diagnosis Synopsis
Cutaneous anthrax is a bacterial infection caused by Bacillus anthracis, an encapsulated, gram-positive, spore-forming bacillus. Although inhalational and gastrointestinal forms of anthrax exist, approximately 95% of all anthrax cases are cutaneous.

B. anthracis has been classified by the CDC as a Category A bioterrorism agent due to its high lethality, hardiness, and ease of weaponization. The spores, which are resistant to heat, UV light, microwave radiation and many otherwise useful disinfectants, can remain dormant in soil for years. If anthrax were to be weaponized, the most likely method of dispersal would be by aerosol release, however the anthrax events of 2001 proved that dissemination of anthrax powder by mail is also an effective dispersal method.

Prior to 2001 there had not been a case of cutaneous anthrax reported in the United States since 1992. There were 11 cases of cutaneous anthrax attributed to the terrorist events of 2001 (7 confirmed, 4 suspected). Cutaneous anthrax should be considered in postal workers and those who handle mail or packages when the patient presentation includes localized vesicles, bullae or eschars.

Cutaneous anthrax lesions evolve from pruritic papules to clusters of vesicles to ulcers within 1 to 2 days following exposure of abraded skin or wounds to the spores. The ulcers then develop into depressed black eschars over the next 2 to 5 days. The most common areas affected are the arms, face and neck. The incubation period is 1 to 12 days.

With antibiotic treatment the mortality rate for cutaneous anthrax is approximately 1%. However, without treatment it may progress to a systemic form of anthrax with a mortality rate of approximately 20%. In these cases, the spores introduced into the body are eaten by macrophages and taken to regional lymph nodes, where they germinate into bacteria. Released into the lymph system, they enter the blood stream causing septicemia-releasing toxins that result in a fatal toxemia.

B. Anthracis is present in both domestic and wild animals throughout the world (mainly in agricultural regions of South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean, and the Middle East) and can be transmitted by their meat, wool or hides. Therefore, veterinarians and those in the meat, wool or hide processing industries are the most at risk for contracting naturally occurring cutaneous anthrax. Anthrax is rarely found in animals in the United States.

In 2002, the United States Department of Defense reintroduced the vaccination of military personnel and essential emergency civilians against anthrax.
Suspected or confirmed cases of cutaneous anthrax must be reported to your local or state department of health.

The CDC recommends avoiding direct contact with the lesion(s) or lesion drainage and using standard contact precautions (gloves, gown, mask, eye protection, and frequent hand washing).

Look For
Look for an initial pruritic macule or papule that enlarges into a plaque. Vesicles in a group or ring then appear, sometimes coalescing into bullae. They can discharge clear to serosanguineous fluid, with numerous organisms seen on gram stain. Then, a painless, depressed black eschar develops at the center, with extensive local edema. The eschar loosens and falls off in 2 to 3 weeks, leaving no permanent scar. Lymphangitis and painful lymphadenopathy are common.

Diagnostic Pearls
A bullous lesion forming a central eschar is typical of the clinical progression.
Take a careful history for possible exposure.

Differential Diagnosis & Pitfalls
Ecthyma gangrenosum
Rat-bite fever
Ulceroglandular tularemia
Plague
Glanders
Rickettsialpox
Orf
Staphylococcal lymphadenitis
Leprosy
Scrub typhus
Buruli ulcer
Mucormycosis
Coumadin necrosis

Best Tests
Gram stain of vesicular fluid
Culture of vesicular fluid
Obtain blood cultures before instituting antibiotic therapy.
PCR

Note:
Coordinate all aspects of testing, packaging, and transporting with public health laboratory/Laboratory Response Network (LRN).

Management Pearls
Antibiotic therapy does not typically change the course of eschar formation and healing. Cutaneous anthrax may occur from handling the organism, so public health authorities should be notified immediately

Therapy
Ciprofloxacin or doxycycline should be considered first line therapy.

NOTE:
Cutaneous anthrax with signs of systemic involvement, extensive edema, or lesions on the head or neck requires intravenous therapy and a multidrug approach as is used in treating inhalational anthrax. See inhalational anthrax treatment recommendations for details.

CDC Cutaneous Anthrax Treatment Recommendations:
Adults:
Ciprofloxacin 500 mg bid
or
Doxycycline 100 mg bid.
Duration of treatment 60 days.*

Amoxicillin 500 mg po tid is an option for completion of therapy after clinical improvement. The oral amoxicillin dose is based on the need to achieve appropriate minimum inhibitory concentration levels.

Children:
Ciprofloxacin 10 to 15 mg/kg every 12 hours (not to exceed 1 g/day)
or
Doxycycline:**
>8 years and > 45 kg: 100 mg every 12 hours
>8 years and < 45 kg: 2.2 mg/kg every 12 hours
<8 years: 2.2 mg/kg every 12 hours.
Duration of treatment 60 days.*

Amoxicillin 80 mg/kg/day divided every 8 hours is an option for completion of therapy after clinical improvement. Oral amoxicillin dose is based on the need to achieve appropriate minimum inhibitory concentration levels.

Pregnant women and the immunocompromised:
Same as dosages as listed above for adults and children. Although tetracyclines or ciprofloxacin are not recommended during pregnancy, their use may be indicated for life-threatening illness. Adverse effects on developing teeth and bones are dose related; therefore, doxycycline might be used for a short time (7 to 14 days) before 6 months of gestation.

* Previous guidelines have suggested treating cutaneous anthrax for 7 to 10 days, but 60 days is recommended in the setting of a bioterrorism attack, given the likelihood of exposure to aerosolized B. anthracis.

** The American Academy of Pediatrics recommends treatment of young children with tetracyclines for serious infections (e.g., Rocky Mountain spotted fever).

Medical Disclaimer:
The information contained in this web page is intended to be an adjunct to traditional medical information sources. It is not intended to be a substitute for professional medical judgment.

Authors and Editors:
Tener Goodwin Veenema PhD, MPH, MS, CPNP