Contagious ecthyma, commonly known as orf or soremouth, is a zoonotic viral skin infection that affects both animals and humans. It often presents as a localized skin lesion and is particularly common among individuals whose occupations involve regular contact with livestock.
Understanding Contagious Ecthyma
Contagious ecthyma is a viral skin disease caused by the orf virus. This virus primarily infects sheep and goats, leading to the development of characteristic lesions around their mouths, muzzles, and sometimes on their eyelids, ears, udders, or feet. In animals, the disease is also referred to as contagious pustular dermatitis or scabby mouth. The virus is notably resilient, capable of persisting in the environment for extended periods, sometimes years, within dried lesion crusts.
How Humans Contract the Infection
Humans typically contract contagious ecthyma through direct contact with infected animals, their lesions, or materials contaminated by the virus. Common risk factors include handling sick animals, particularly sheep and goats, or coming into contact with contaminated items like wool, hides, pens, feeders, or equipment. Even contact with live orf vaccines, which contain the virus, can lead to human infection.
Occupational groups frequently exposed to the virus include farmers, veterinarians, sheep shearers, and butchers, along with anyone involved in bottle-feeding young lambs or processing animal carcasses. Children visiting petting zoos or farms can also acquire the infection.
Recognizing Symptoms and Progression
Upon infection, humans typically develop a single skin lesion. After an incubation period of 3 to 7 days, the lesion begins as a small, firm, red or reddish-blue papule at the site of virus entry. This initial papule then progresses through distinct stages, often becoming a raised nodule with a central depression or blister. The lesion may appear target-like, featuring a red or necrotic center surrounded by a white ring and a red outer halo.
As the infection progresses, the blister may weep fluid before forming a thick, dry crust or scab. These lesions most commonly appear on the hands, fingers, or forearms, but can also occur on the face. The fully developed lesion can range from 2 to 3 centimeters in diameter, sometimes growing up to 5 centimeters. While the lesion itself may be tender or itchy in the early stages, systemic symptoms like fever or swollen lymph nodes are usually mild and short-lived. The infection is self-limiting, generally resolving spontaneously within 3 to 6 weeks as the crust falls off, revealing new skin underneath.
Treatment and Prevention
There is no specific antiviral treatment for contagious ecthyma in humans, as the infection typically resolves on its own without intervention. Management focuses on alleviating discomfort and preventing secondary bacterial infections. This often involves keeping the lesion clean and dry, using local antiseptics, and taking pain relief medications like acetaminophen or ibuprofen for discomfort. Topical or systemic antibiotics may be prescribed if a secondary bacterial infection develops, indicated by increased redness, pus, or swollen lymph nodes. In rare instances of persistent, growing, or severe lesions, particularly in individuals with weakened immune systems, treatments such as topical cidofovir, imiquimod, or surgical removal may be considered.
Preventing contagious ecthyma involves practical measures to minimize exposure to the virus. Individuals who handle sheep or goats, especially those with visible lesions, should wear nonporous gloves to protect their skin. Practicing good hand hygiene by washing hands thoroughly with soap and water after any animal contact is also important. Any existing cuts or abrasions on the skin should be covered with waterproof bandages before handling animals or contaminated materials. Additionally, avoiding contact with recently vaccinated animals, as they can shed the live vaccine virus, helps reduce transmission risk.