QUESTIONS: A 37-year-old woman has a 2-week history of a blistering lesion on her right hand. She is a sheepherder's wife, and many of the sheep on their farm have come down with an illness that they call “sore mouth.” The dome-shaped bulla with central crusting (see figure) is tender to touch.
What is the diagnosis?
How is the diagnosis confirmed?
What are the typical clinical features of the disease?
What is the treatment?
ANSWERS:
THE DIAGNOSIS
The patient has human orf, also known as ecthyma contagiosum. The disease is a zoonosis that is picked up from sheep or goats, and it is caused by a Parapoxvirus species. The virus is transmitted to humans by direct inoculation of infected animal material through the skin.
Human orf is most commonly seen in shepherds, veterinary surgeons, farmers' wives who bottle-feed lambs, meat industry workers who handle pelts and wool, and butchers. The diagnosis is made on the basis of the clinical presentation, the location of the lesion (usually on the hands), and a history of exposure to sheep or goats.1
Outbreaks in Turkey and Belgium have occurred 2 to 3 weeks after the Islamic “Feast of Sacrifice” in men who bleed the sheep and women who manipulated the skin and meat of the animal.2
CONFIRMING THE DIAGNOSIS
The diagnosis is confirmed by using electron microscopy to look directly for the viral particles in the crust of the lesion or a small biopsy specimen.3 Vesicle fluid contains little evidence of the virus. Levels of orf virus antibody detected by enzyme-linked immunosorbent assay (ELISA) increase during infection. This rise in antibody level can be confirmed by Western blot assay. Previous exposure to vaccinia virus (smallpox vaccination) provides no protection from subsequent infection with orf.4
CHARACTERISTIC CLINICAL FEATURES
After an incubation period of 3 to 7 days, a small, firm reddish blue papule forms on the skin surface. This lesion enlarges to form a hemorrhagic pustule or bulla that typically measures 2 to 3 cm in diameter but may grow to 5 cm in diameter. The center often is crusted with a surrounding, characteristic grayish white or violaceous ring, which in turn is encircled by a zone of erythema.5 Ninety-five percent of lesions are on the hand, but they occasionally occur on the face and eyelids. Reinfection has been reported.6
TREATMENT
Treatment usually is not necessary because lesions typically resolve spontaneously in 4 to 6 weeks. Secondary infection should be treated with appropriate antibiotics.
Liquid nitrogen cryosurgery speeds resolution,7 and razor blade shave excision is effective when lesions persist.8 Corticosteroid therapy, irradiation, and amputation should be avoided.9
Freeman and colleagues described a case of orf virus infection of the pericanthal eyelid skin and conjunctiva, diagnosed by electron microscopy. The patient was a farmer's wife who had recently handled lambs. She had a raised ulcerating lesion at the inner canthus, follicular conjunctivitis, and lymphadenopathy. Treatment with 35% idoxuridine in dimethylsulfoxide on the skin and 0.5% idoxuridine ointment on the conjunctiva led to resolution after 3 weeks.10
Figure 1.
Painful bulla on the right hand has central crusting
Competing interests: None declared
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