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Two viral skin diseases are rarely transmitted from animals to humans.
Contagious
ecthyma:
Contagious ecthyma (contagious pustular dermatitis) is caused by orf virus, a poxvirus that infects ruminants (most often sheep and goats). Farmers, veterinarians, zoo caretakers, and others with direct animal contact are at risk. The cutaneous findings pass through 6 stages that last about 1 wk: (1) papular, a single red edematous papule appears on a finger (most commonly right index finder); (2) target, a larger nodule with a red center surrounded by a white ring with a red periphery; (3) acute, a rapidly growing infected-looking tumor; (4) regenerative, a nodule with black dots covered with a thin transparent crust; (5) papillomatous, a nodule with a surface studded with small projections; (6) regressive, a nodule flattened with a thick crust. Patients can develop regional adenopathy, lymphangitis, and fever.
Diagnosis is by history of contact; differential diagnosis is extensive depending upon the stage of the lesion. Acute lesions must be differentiated from milker's nodules, mycobacterium marinum, and bacterial infection; regressed lesions must be differentiated from cutaneous tumors, such as Bowen's disease or squamous cell carcinoma. Lesions spontaneously heal; no treatment is necessary.
Milker's
nodules:
These are caused by paravaccinia virus, a parapoxvirus that causes udder lesions in cows. Infection requires direct contact and produces macules that progress to papules, vesicles, and nodules; 6 stages have been described similar to contagious ecthyma. Fever and lymphadenopathy are uncommon. Diagnosis is by history of contact and cutaneous findings. Differential diagnosis varies depending upon morphology but includes primary inoculation TB, sporotrichosis, anthrax, and tularemia. Lesions heal spontaneously; no treatment is necessary.
Last full review/revision November 2005
Content last modified November 2005
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