Anthrax - skin

Alternative names
Cutaneous anthrax

Definition
Cutaneous anthrax is an infection of the skin caused by direct contact with the bacterium Bacillus anthracis.

Causes, incidence, and risk factors

Anthrax is caused by the bacterium Bacillus anthracis. While anthrax commonly affects hoofed animals such as sheep and goats, humans may acquire this disease as well. Cutaneous anthrax is the main form of anthrax worldwide, accounting for 95% of all anthrax cases.

Historically, the main risk factor for acquiring cutaneous anthrax is contact with animal hides or hair, bone products, and wool, as well as contact with infected animals. Hence, the populations most at risk for anthrax include farm workers, veterinarians, and tannery and wool workers.

Cutaneous anthrax is an anthrax infection of the skin. The disease occurs after the bacteria contact skin cuts or abrasions. Usually within two weeks, an itchy skin lesion develops (similar to an insect bite). This lesion may later blister and then break down, resulting in a black ulcer, which is frequently painless. The skin lesion is usually surrounded by significant swelling. Sometimes painful lymph nodes may develop. A scar is often formed, which then dries and falls off within two weeks.

In 20% of UN-treated individuals, the infection may spread through the bloodstream and become fatal. However, in most individuals who receive appropriate treatment, death is extremely rare.

Anthrax is a potential agent for use as a biological weapon or for bio-terrorism. While at least 17 nations are believed to have a biological weapons program, it is unknown how many nations or groups are working with anthrax. Most bio-terrorism experts have concluded that it is technologically difficult to use anthrax effectively as a weapon on a large scale.

Cutaneous anthrax would most likely occur by direct contact of anthrax spores with non-intact skin.

Symptoms

     
  • Papule, blister, ulcer with black scab; often with extensive surrounding swelling  
  • A few patients may also experience fever, headache, and malaise  
  • Swollen, painful lymph nodes may also develop

Signs and tests

     
  • If cutaneous anthrax is suspected, a culture of the skin lesions should be done to identify the bacteria that causes anthrax.

Treatment

The mainstay of treatment is early antibiotic therapy. Several antibiotics are effective, including penicillin, doxycycline, and ciprofloxacin (Cipro). If an outbreak of anthrax is suspected, the antibiotic of choice is ciprofloxacin, until it is known whether the anthrax strain is resistant to any of the other usual antibiotics. Because spores may take up to 60 days to germinate, the length of treatment is usually 60 days.

Cutaneous anthrax is treated with oral antibiotics (pills).

In the event of a bio-terrorist attack, the National Pharmaceutical Stockpile is available to supplement and help provide antibiotics should a shortage occur.

Expectations (prognosis)

The prognosis of treated cutaneous anthrax is excellent, as death is extremely rare when antibiotics are given.

In UN-treated cutaneous anthrax, up to 20% of cases are fatal.

Complications

     
  • In 20% of untreated cases of cutaneous anthrax, the organism may spread into the bloodstream and lead to shock and death.

Calling your health care provider

Notify your health care provider if you have had an exposure to anthrax and you develop a skin lesion as described above. While there are several illnesses which may cause similar lesions, you will need a medical evaluation to sort out the underlying cause.

Prevention

There are two primary modes of prevention of anthrax.

For individuals who have been truly exposed to anthrax (but have no signs and symptoms of the disease), preventive antibiotics may be offered, such as ciprofloxacin, penicillin, or doxycycline, depending on the particular strain of anthrax.

Vaccination has also been developed and is given in a 6-dose series. This vaccine is mandated for all U.S. military personnel. It is currently not available, nor is it recommended, for use in the general public.

THERE IS NO KNOWN TRANSMISSION OF CUTANEOUS ANTHRAX FROM PERSON TO PERSON. Household contacts of individuals with anthrax do not need antibiotics unless they have also been exposed to the same source of anthrax.

Johns Hopkins patient information

Last revised: December 7, 2012
by Mamikon Bozoyan, M.D.

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