Contagious ecthyma is a common skin disease in sheep and goats caused by a parapoxvirus. It mainly affects the mouth, nostrils, and feet, and can spread quickly within a flock, especially among young lambs. Due to its contagious nature and recurring outbreaks, effective control and timely vaccination are essential to reduce economic losses and ensure animal welfare.
Etiology of Contagious Ecthyma:
Contagious ecthyma, also known as Orf, is caused by the orf virus, the prototype of the Parapoxvirus genus within the Poxviridae family. This group also includes viruses like bovine papular stomatitis virus (parapox bovis 1), pseudocowpox virus (parapox bovis 2), and a parapoxvirus found in deer. The orf virus is highly resilient, remaining viable for over 15 years at room temperature due to its strong resistance to drying. Molecular analysis, including restriction enzyme digestion of its DNA, reveals notable genetic variability among different field strains.
Epidemiology of Contagious Ecthyma:
Occurence
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Occurs worldwide in sheep and goats.
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Most common in 3–6-month-old lambs, but can affect animals of any age.
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Outbreaks often involve the lips and face of lambs, the udders of ewes.
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More frequent during dry seasons, in feedlots, or with trough-fed sheep.
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Has been reported in wild species: musk ox, reindeer, mountain goats, bighorn sheep, chamois, caribou, Dall sheep, buffalo, wild goats, and camels.
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Zoonotic: humans, especially farmers and abattoir workers, can get infected through contact.
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The virus can infect rabbits (via scarified skin) and chick embryos (9–12 days old).
Morbidity and Case Fatality
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Morbidity in outbreaks can approach 100% in sheep and goats.
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Case fatality ranges from 5–15%, often due to respiratory lesion complications or secondary infections like flystrike.
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In rare systemic outbreaks, fatality can reach 25–75%.
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Recovered animals usually gain 2–3 years of immunity, but no colostral immunity is passed to lambs, leaving newborns vulnerable.
Methods of Transmission
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Virus persists in scabs that fall off from healing lesions—infective for long periods in dry conditions.
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Chronic lesions in animals may act as persistent virus reservoirs.
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Transmission is rapid via:
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Direct contact with infected animals
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Contaminated objects (e.g., feed troughs, tagging tools)
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Docking instruments used on the tails
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Natural infection often follows skin trauma (e.g., from stubble or prickly plants).
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Transport-related outbreaks may occur even without visible injury.
Zoonotic Implications
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Lesions typically appear on hands, arms, or face after contact with infected sheep or scabby mouth vaccine.
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Human lesions are itchy, self-limiting, and usually heal in 6–7 weeks.
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Risk also exists in petting zoos and fairs, especially when children handle or feed lambs.
Risk Factors
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Main risk factors:
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Presence of a virus in the environment
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Immune status of individual animals
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Mixing of animals (e.g., in feedlots) increases transmission risk.
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Co-infections, such as with border disease virus or Ehrlichia phagocytophila, can worsen the severity and prolong the disease course.
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Persistent carriers can spread the virus to naive animals, even if asymptomatic.
Clinical Signs:
Orf Virus in Sheep – Clinical Signs
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Small raised spots appear early in infection.
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Sores develop into fluid-filled blisters and later thick crusts.
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The first symptoms show near the corners of the mouth.
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Lesions may expand to the lips, nostrils, and facial hair.
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Lips become swollen, causing feeding problems in lambs.
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Pain from sores limits nursing and grazing behavior.
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Mild cases heal on their own in around three weeks.
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Nursing can spread the virus to the mother’s teats.
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Crusted sores on teats can lead to udder infections.
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Temporary infertility can occur due to fluid buildup.
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Feet may show signs of infection near the hoof edges.
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Swelling of the face may resemble bluetongue symptoms.
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In rare situations, the virus moves to internal organs.
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Digestive issues or breathing trouble may develop.
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Young lambs can get red, painful ulcers inside the mouth.
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Some breeds may show raw, overgrown sores without scabs.
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Severe form may cause mouth blisters and hoof damage.
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Rarely, sores form at the edge of heat-damaged skin.
Orf Virus in Goats – Clinical Signs
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Infection often follows contact with infected surfaces.
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Lesions usually appear on the face, neck, and body.
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Mouth, udder, and teat involvement is uncommon.
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Patches begin as raised areas and become hard crusts.
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Crusts fall off naturally, leaving bald or pale skin.
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Hair usually grows back over time.
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Most goats recover in three to six weeks without help.
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In a few cases, lesions last for months in some goats.
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Long-lasting disease may be due to the goat’s immunity.
Differential diagnosis of contagious ecthyma:
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Ulcerative dermatosis
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Mycotic dermatitis (Strawberry footrot)
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Facial eczema
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Papillomatosis (warts)
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Bluetongue
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Sheeppox
Treatment of contagious ecthyma:
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Removing crusts and using topical ointments or astringents can delay skin healing.
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Antiviral agents like cidofovir combined with healing gels (e.g., sucralfate) may reduce viral shedding and speed recovery.
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These antiviral treatments are usually not practical or affordable for large flocks.
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Supportive care, such as offering soft, easy-to-eat feed, can assist affected animals.
Control and Vaccination of Contagious Ecthyma:
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Isolate infected animals and vaccinate healthy ones early in outbreaks.
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Vaccination is ineffective if most animals are already infected.
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For recurring cases, vaccinate lambs at 6–8 weeks of age.
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Newborn lambs can benefit from early vaccination; vaccinating ewes offers no lamb protection.
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Indoor lambs should be vaccinated before typical outbreak seasons.
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Applied by scratching into bare skin or via scarification/ear-prick methods.
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Immunity develops within 3 weeks; check for local skin reaction after 7 days.
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No reaction may signal an inactive vaccine or existing immunity.
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Lambs may develop mild sores from licking vaccine sites.
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Removing rough materials helps, but is often impractical.
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Avoid routine vaccination in disease-free flocks to prevent vaccine-spread outbreaks.
Conclusion:
Contagious Ecthyma is a contagious skin disease that primarily affects sheep and goats, though it can occasionally spread to humans through direct contact. Caused by a parapoxvirus, this disease is characterized by scabby, wart-like lesions around the mouth, nostrils, and sometimes the legs or udders. It tends to occur more frequently in young animals and is commonly associated with poor hygiene, overcrowding, and skin injuries. Orf is globally widespread and is often seen in flocks during lambing or kidding season . Contagious Ecthyma remains a significant health concern in livestock management due to its contagious nature, zoonotic potential, and recurring presence in infected flocks. Prevention through proper hygiene, early isolation of infected animals, and timely vaccination of young stock plays a vital role in controlling its spread.
FAQs
Q1. What animals are most commonly affected by Orf?
Sheep and goats are the most commonly affected animals, especially young ones.
Q2. Is Orf dangerous to humans?
Yes, Orf can be transmitted to humans, usually causing mild skin lesions, especially in people handling infected animals without protective gear.
Q3. How is Orf transmitted among animals?
Orf spreads through direct contact with infected animals or contaminated surfaces, especially when skin is damaged.
Q4. Can animals recover from Orf without treatment?
Yes, most animals recover naturally within a few weeks, though supportive care can speed healing and reduce discomfort.
Q5. How can Orf be prevented?
Good hygiene, isolating infected animals, minimizing skin injuries, and vaccinating at-risk animals can help prevent outbreaks.
