John is a 62 year old male presents with complaints of a sore on his right middle finger that he has had for 4 days and it is getting worse. The patient denies pain, fevers, chills, body aches, or recent trauma. He reports that some redness and streaking is also starting to go up his right hand and arm. No other family members have any sores or rashes. He is a retired teacher and spends his time working on his small family farm in Vermont that has been in the family for 4 generations. They raise pigs, chickens, sheep, alpacas, and grow a variety of vegetables. He also works with animal hides to make traditional drums. His wife and daughter also sell handmade hats, sweaters , scarfs and mittens from the alpaca and sheep wool. He denies having any other rashes, lesions or recent illnesses. His only medical problem is hypertension which is well controlled with lisinopril. What’s your diagnosis?
a. staph infection b. brown recluse spider bite c. anthrax. d. yersinia pestis
Answer: Cutaneous anthrax
Anthrax is extremely rare in the developed world but sporadically occurs among farmers, wool workers, butchers and gardeners. Anthrax primarily affects sheep and cattle that ingest spores lying dormant in the pasture. Anthrax spores can survive for over 20 years in dry pasture and soil. Human infection can arise from spores entering the skin by inoculation through a minor injury. Most anthrax infection (95%) is via the skin (cutaneous anthrax).1
Cutaneous anthrax develops usually between 1-7 days after skin exposure. Most often anthrax starts as a localised infection on exposed skin. The incubation period is usually 5 to 7 days with a range of 1 to 12 days. It can also mimic an insect bite. Usually it is painless, and an itchy bump appears with surrounding redness. After a day or so, it blisters then ulcerates. The sore then expands and develops smaller blisters and redness and can develop black scab. Within a couple of weeks, the infection heals leaving a scar.3
The CDC has developed recommendations for the clinical evaluation of persons with possible cutaneous anthrax.
-For vesicular lesions, two swabs of vesicular fluid from an unopened vesicle, one for Gram stain and culture, the second for PCR testing
-For eschars, the edge should be lifted and two swabs rotated underneath and submitted, one for Gram stain and culture, the second for PCR testing
-For ulcers, the base of the lesion should be sampled with two saline-moistened swabs and submitted, one for Gram stain and culture, the second for PCR testing.2
Cutaneous anthrax is treated with antibiotics. Treatment has been with intravenous or intramuscular penicillin for 7–10 days. However, for uncomplicated cutaneous anthrax, an oral tetracycline, especially doxycycline, is given in an outpatient setting.1