Orf
Orf is a skin infection caught from sheep and goats. Medical notes call it contagious ecthyma or contagious pustular dermatitis, and people who work with…
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Orf is a skin infection caught from sheep and goats. Medical notes call it contagious ecthyma or contagious pustular dermatitis, and people who work with livestock simply call it the lamb sore. The virus produces a single nodule, usually on a finger, hand, forearm or face; the nodule grows, weeps, crusts over and clears by itself in about six weeks. In itself it is not dangerous, and the job of this page is a different one: not to mistake it for a lookalike that is dangerous, and not to let bacteria into the wound.
Where it comes from
The cause is a parapoxvirus that lives in young lambs and kids. In the animal it produces scabs around the muzzle and mouth, sometimes on the legs and udder; sheep and goats pass it between themselves easily, though the illness is not usually serious for them. A lamb with sores on its lips damages the mother's udder, and the infection travels through a flock quickly.
People catch it through broken skin: a graze, a cut, a torn hangnail, a scratch. Touching an animal's muzzle, its bedding, a trough, a knife, a fence or the fleece is enough — the virus survives a long time on objects and in dried scabs. Anyone in regular contact with these animals is exposed: farmers, vets, shearers, abattoir workers, butchers, along with anyone bottle-feeding a lamb and families who slaughter a sheep at home for a festival.
One point deserves separate mention: sheep and goats are vaccinated against orf with a live vaccine, and a recently vaccinated animal sheds virus for a while. Handling a freshly vaccinated flock bare-handed is as risky as handling a sick one.
Passing orf from one person to another is extremely rare. Having had it leaves partial protection: you can catch it again, but it is usually milder and quicker. There is no vaccine for people.
What it looks like and how it changes
Three days to a week pass between contact and the first change in the skin. There is usually one nodule, sometimes two or three, matching the number of places the virus got in. From there it runs through a fairly recognisable sequence, looking different at each stage:
- first a small firm spot or bump, reddish-blue, or simply darker than the surrounding skin on brown or black skin; it itches slightly or is tender to press;
- over a week or two it enlarges and takes on a target shape: a dark centre, a pale ring around it and a red rim outside that;
- then the surface softens and the nodule weeps clear or cloudy fluid;
- after that it dries and forms a hard crust, sometimes with a rough warty surface;
- finally the crust separates and the skin underneath heals.
The usual size is two to three centimetres, occasionally up to five. The whole course takes around six weeks. A flat mark or a barely visible scar may be left behind. General symptoms do not appear in everyone: a mild fever, feeling washed out, and enlarged tender glands on the inner side of the elbow or in the armpit on the affected side.
What else looks like this
This is the most important part of the page. A sore on the hand of someone who works with livestock is not always orf, and some of its lookalikes need entirely different treatment:
- cutaneous anthrax — the reason this list exists at all. It too starts as a small bump on the hand or face of someone who has handled sheep, goats, hides or wool. Three things set it apart: the ulcer is painless, a dry black scab forms in the centre, and wide soft swelling spreads around it, often with fever and feeling unwell. It is treated with antibiotics that must be started early, so that combination means seeing a doctor the same day;
- milker's nodule — a near-identical twin of orf, only the virus is a different one and it comes from cattle. It runs the same course and clears by itself in the same way;
- herpetic whitlow — a cluster of small blisters on a red base appears on a finger, the pain is severe and throbbing, and the whole thing tends to come back in the same spot;
- tularaemia — an ulcer plus markedly enlarged, painful glands and fever; caught from rodents, hares or insect bites;
- atypical mycobacterial infection — a sluggish nodule that drags on for months; the classic history involves a fish tank or gutting fish;
- an ordinary pus-filled whitlow, or cellulitis — here the pain builds over hours and days, the skin is hot and the redness spreads;
- keratoacanthoma and squamous cell skin cancer — a nodule with a horny plug still not healed at two or three months. Orf does not do that: it is obliged to go.
A doctor usually diagnoses orf from the look of the lesion and the story of animal contact. If the picture is doubtful or the nodule will not go, a swab for the virus or a piece of tissue for examination is taken.
What to do with the sore
No medicine kills this virus, and none is needed: the body deals with it. The task is to stay out of its way and keep bacteria out.
- cover the nodule with a waterproof dressing, change it when it gets wet, and keep the skin around it clean and dry;
- do not open or squeeze it: there is no pus inside, but bacteria are easily introduced that way;
- wash your hands after every dressing change and do not rub your eyes with that hand — the virus on an eyelid causes an unpleasant inflammation;
- take rings off the affected finger while it is swollen, so that they do not constrict it;
- an ordinary painkiller such as paracetamol will do for the discomfort. It relieves pain but does not treat the infection, so judge the state of the sore by how it looks, not by whether it hurts.
Antibiotics do nothing to orf itself — they are needed only when bacteria have joined in on top. If the nodule is still there at six weeks or keeps growing, a doctor may suggest freezing, curettage or a small excision; those decisions follow an examination and sometimes a biopsy.
Who gets a harder time of it
In someone with weakened defences — with HIV, during chemotherapy, on medicines that suppress immunity after a transplant — orf behaves differently: there may be many nodules, they grow to several centimetres, they fail to heal for months and they need specialist treatment. Those people should see a doctor from the outset rather than waiting six weeks.
Complications also occur in healthy people, and their warning signs are more use than their names:
- bacterial infection of the sore: pain increases sharply, pus comes from under the crust, redness spreads beyond the nodule, a red line runs up the arm and a fever starts. On brown or black skin redness is harder to see, so go by the swelling, the heat and the pain;
- erythema multiforme: a week or two after the illness begins, round target-shaped patches — dark centre, pale ring, dark rim — break out over the body, chiefly on the hands, forearms and lower legs. The rash is symmetrical and usually settles on its own; but if painful sores appear at the same time in the mouth, on the lips or in the eyes, a doctor is needed the same day;
- a blistering eruption: rarely, orf is followed by a rash of large tense blisters on itchy skin. That is a separate condition needing assessment and treatment, not a continuation of the sore.
How to avoid catching it
- handle sheep and goats in gloves — latex, or nitrile if latex causes a reaction; this applies to bottle-feeding lambs too;
- cover cuts, grazes and torn hangnails with a waterproof dressing before starting work, not afterwards;
- wash your hands with warm water and soap after any contact with the animals, their bedding and the equipment;
- remember recently vaccinated animals: they shed live virus and must not be handled bare-handed;
- vaccinate the flock and keep affected lambs away from healthy ones;
- clean and disinfect pens, troughs, drinkers and working equipment regularly: the virus survives well in dried scabs and on objects;
- do not let children stroke lambs with scabs on the muzzle — at petting farms that is the usual source of infection.
When to see a doctor
See a doctor the same day if:
- the ulcer does not hurt, has a black scab in the centre and wide swelling around it, particularly with a fever — that is how cutaneous anthrax presents, and it needs antibiotics straight away;
- the pain has sharply worsened, pus is coming out, the redness is spreading, a red line runs up the arm, the glands are enlarged and painful and there is a fever;
- the nodule is on an eyelid or at the edge of the eye;
- your immunity is weakened, by illness or by treatment;
- there are many nodules, they are large and painful, or they keep coming back;
- six weeks have passed and the sore is not healing or is still growing.
Call an ambulance (in Spain, Italy, Portugal, Poland and Ukraine, 112) in the rare but serious cases: if chills with a high fever and confusion appear; if redness and swelling advance while you watch; if the skin over them has turned purplish and the pain is far greater than the look of the sore would explain — that is how a deep soft tissue infection begins. An ambulance is also needed for sudden swelling of the lips, tongue or throat with difficulty breathing.
Online consultation
Orf is precisely the case where a photograph and an account are usually enough for a clear answer. The doctor looks at the sore, asks about contact with animals, about timings and about how the nodule is changing, and says the essential thing: whether this looks like orf that simply needs covering and waiting out, or like something else that warrants being seen in person and today. Along the way you get the practical points — how to dress it, what to take for the pain, what to do about work on the farm, how to protect the rest of the household.
What an online appointment cannot replace: examination, if the sore has not healed after six weeks or is growing; a swab for the virus and a biopsy, when the picture is unclear; face-to-face care where anthrax or a spreading bacterial infection is suspected.
This material is for information only and does not replace medical advice.
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