Ecthyma contagiosum

Synonyms

Orf, bovine pustular stomatitis. Orf and milker’s nodule are caused by two closely related parapoxviruses; they are clinically very similar and transfer in both cases is from an infected animal to a human.

Epidemiology

Worldwide. Prevalence of the disease in 15% of sheep, especially in young lambs. Persons at risk are farmers, vetenarians, shearers, sheepherders, and butchers. Poxviruses are endemic in large parts of Africa (Democratic Republic of the Congo).

Definition

Zoonotic infection of the skin caused by the parapoxvirus, Orfviridae, contracted from sheep, lambs and goats.

Aetiology & Pathogenesis

By direct or indirect contact with diseased animals the highly contagious zoonotic virus parapoxvirus ovis is transmit. It stimulates angiogenesis by viral vascular endothelial growth factor E (VEGF-E). No human-to-human transfer.

Signs & Symptoms

Single lesion, developing through several stages after inoculation: erythematous macule, inflamed pustular lesion with central necrosis and peripheral red halo; regression after 4-6 weeks and healing, mostly without scar. In addition, there may be fever, malaise, and regional lymphadenopathy. In immunocompromised patients autoinoculation and multiple “giant” lesions may occur.

Localisation

They occur most commonly on the fingers, hands or forearms but can appear on the face or mucous membranes as well.

Classification

Poxviruses

Orthopoxviruses
- Smallpox
- Vaccinia
- Cowpox
- Monkey pox
Parapoxviruses
- Ecthyma contagiosum (orf)
- Milker’s nodule

Molluscum Contagiosum

Laboratory & other workups

The relatively large virus can be identified by electron microscopy, by special culture or by PCR.

Dermatopathology

Prominent reticular degeneration and necrosis of the epidermis.
Ballooning, and necrosis of keratinocytes.
Blister formation may be minimal. Multinucleated giant cells usually are absent.

Accompanying papillary edema with erythrocyte extravasation and inflammatory infiltrate.

Course

Spontaneous healing without scar within 6-8 weeks.

Complications

Secondary bacterial infection with lymphangitis and erysipelas. Development of erythema multiforme in 10-20% of patients 3-4 weeks after inoculation or of other immunological reactions like Stevens‐Johnson syndrome or blistering disorders.

Diagnosis

History (animal contacts); typical clinical feature.

Differential diagnosis

Poxvirus infections; variola vera; monkey pox; milker’s nodule; pyogenic granuloma; bacillary angiomatosis; impetigo contagiosa; dermatitis due to mites; varicella; pustula maligna (anthrax).

Prevention & Therapy

Prevention of contacts with infected animals. The lesions are self-limiting in immunocompetent patients.

Topical: drying measures and topical antiseptics usually are sufficient. In immunocompromised patients topical cidofovir along with mechanical eradication (i.e., cryotherapy, surgical excision, imiquimod, etc.) may be applied.

Special

None.

2.1.7 Ecthyma contagiosum