17 Mar 2026
Emily Collins-Wingate BVMSci, MRCVS looks at treating a disease that can severely impact sheep flocks.
Emily Collins-Wingate
Job Title
Contagious pustular dermatitis (contagious ecthyma, scabby mouth and sore mouth, but hereafter referred to as orf) is a skin disease caused by a Parapoxvirus species, with worldwide distribution. Orf mainly affects sheep and goats, and results in proliferative skin lesions commonly seen around the nose, mouth and ears of sheep, and on the teats of ewes (Bala et al, 2018; Scott, 2009).
Orf prevalence in England has previously been estimated at 2% in ewes and 20% in lambs. The disease is highly contagious and can spread rapidly – especially in a naive flock (Onyango et al, 2014). The disease is considered self limiting, with outbreaks typically lasting six to eight weeks (Spyrou and Valiakos, 2015). Morbidity within individual flocks is often more than 50%, though it is not uncommon for it to reach 100% (Lewis, 1996; Reid and Rodger, 2007).
Mortality for uncomplicated cases is less than 1%, but where secondary factors such as immunosuppression or concurrent disease are present, this can reach 50% (Scagliarini et al, 2012).
Orf initially presents as erythematous lesions around the mouth and nostrils, approximately one week after exposure to the virus. These develop into vesicles, papules and exudative pustules which then form dry scabs that are eventually shed, spreading infective material in the surrounding environment (Reid and Rodger, 2007).
Transmission of orf occurs between sheep (or goats) through direct contact of animals or contact with fomites such as handling facilities or equipment. Orf is a zoonotic disease that can affect humans by direct or indirect contact with infected animals or contaminated materials (Spyrou and Valiakos, 2015).
Minimising the spread of orf within a flock relies on biosecurity practices such as strict hygiene and isolation protocols.
Measures that may be implemented include:
In the UK, a live attenuated orf vaccine is available for immunisation of adult sheep and neonates to reduce the severity of clinical signs (NOAH, 2025). Vaccine shortages have become increasingly common in recent years, with orf vaccine also affected. This has resulted in veterinary practices advising farmers to “plan ahead” to secure the vaccine if it is required after three years of vaccine shortages (Priestley, 2024).
The NOAH Livestock Vaccination Guideline lists orf vaccination as a “category two” vaccine for sheep in the UK. Livestock vaccines in this category are usually recommended as best practice, but use is dependent on farmer and vet review and discussion (NOAH, 2022).
Vaccination takes place by skin scarification, which produces vesicles and pustules at the vaccination site. As this is a live vaccine, the shedding of these scabs can contaminate the environment and lead to infection of stock if they have not previously been exposed to the virus (AHDB, 2025). For this reason, vaccination is only recommended in flocks that are endemically infected with orf (NOAH, 2022).
Small et al (2019) highlighted inconsistencies in farmer compliance with orf vaccination guidelines, with only 27% of survey respondents using the correct vaccination site as indicated on the data sheet (axilla). These results demonstrated that vaccination is not carried out correctly on all UK sheep farms, which is likely to affect vaccine efficacy.
It is well known within the veterinary and farming professions that orf is a zoonotic disease with significant human health impact. Reilly et al (2025) found 75% of respondents worried about contracting orf, and 30.2% had previously contracted it. Despite this, one-third of survey respondents reported never wearing gloves when handling sheep.
Management of an orf outbreak is challenging, as no UK-licensed treatments for orf are currently available. Treatment of affected individuals is typically supportive care, with topical or systemic antibiotics sometimes administered to manage secondary bacterial infections of the orf lesions.
Reilly et al (2025) found 68.4% of respondents were using antibiotics as part of their first-line treatment for orf; 65.2% used topical aerosolised antibiotics (typically oxytetracycline products) and 26.7% used injectable systemic antibiotics. Lovatt et al (2012) found approximately 10% of lambs affected by orf received systemic antibiotics in addition to aerosolised antibiotics with the aim of treating secondary bacterial infections.
Routine antibiotic usage for managing a viral disease cannot be justified. Antibiotics should only be used in cases of orf when secondary bacterial infection has occurred. The Veterinary Medicines (Amendment etc) Regulations 2024 for England, Wales and Scotland prohibit the use of routine prophylactic antibiotics. Administering antibiotics to animals affected by orf with the aim of “preventing” secondary bacterial infection may be considered prophylactic use of antibiotics by the RUMA-suggested definition of prophylaxis/preventive treatment (RUMA, 2022).
It should also be noted that topical antibiotics are ineffective for prophylaxis, as widely evidenced in veterinary and human literature (Cavalli et al, 2025; Chen et al, 2021; Levender et al, 2012).
Defra’s livestock population report from June 2025 found England had 6.4 million breeding ewes and 6.5 million lambs younger than one year old (Defra, 2025). Working from the estimated prevalences of 2% in ewes and 20% in lambs, as reported in Onyango et al (2014), that would result in 128,000 ewes and 1.3 million lambs affected with orf annually.
A 2025 survey with 421 respondents found 88% had been affected by orf on their farm, with 73.3% having had a case in the past 12 months. This suggests a much higher proportion of UK flocks could be affected each year than previously estimated. Flocks which had seen orf reported that occurrence was considerably higher in lambs (78.3% to 90.3%) than in adult ewes and rams (50% and 10.9%, respectively).
Despite the high prevalence, only 23.4% of respondents used orf vaccination on their holding (Reilly et al, 2025).
It has been widely acknowledged that the economic impacts of orf are vast due to factors including reduced growth rates of affected lambs, secondary mastitis of ewes, and increased feed and labour requirements of supplementary feeding lambs. In 2003, the estimated cost of orf to the British economy was £10 million annually; however, more recently the losses were estimated at between £1.06 million and £14.03 million annually (Bennett, 2003; Lovatt et al, 2012).
Farmer reports on the financial costs associated with orf were also collected in Reilly et al (2025) and responses ranged from £0 to £20,000, with a median cost to the flock of £100.
The top three reported areas for losses were:
Farrow (2025) estimated the cost of antibiotic treatments to be £0.40 per topical aerosolised antibiotic and £0.75 per systemic antibiotic injection – this did not account for the use of any anti-inflammatory treatment.
Recently, a zinc-based hydrophobic gel-barrier product (Ambugreen; NoBACZ Healthcare) has been applied to the lesions of affected sheep with reportedly good results. A gloved finger is used to apply a 2mm to 3mm layer of the adhesive gel product over the orf lesions, which forms a hydrophobic, non-colonisable, physical barrier over the site where it is applied.
Farrow (2025) applied the gel product to lesions on lambs across five farms to assess its effectiveness in managing orf lesions in lambs. The product was found to be beneficial to the resolution of all orf lesions of varying degrees of severity, with “healing being notably quicker than expected in mild cases” following a single application of product. Severe lesions were also greatly improved: drier, with reduced or no bacterial infection apparent.
A flock with 80% morbidity in ewes pre-lambing also had the gel applied, with the aim of resolving the lesions before lambing; 70% of the affected sheep improved significantly from one application of product, with 30% having a second application a week later due to more severe lesions.
The farmer felt the gel-barrier product had helped reduce the transmission of orf within the flock, and it also meant no antibiotics were required, as none of the affected animals developed secondary bacterial infections (Collins-Wingate, 2025).
Upon application, the product has the consistency of a viscous gel, making it easy to spread over affected lesions. This gel provides an instant waterproof layer that gradually hardens, forming a flexible and protective covering (Bastos et al, 2020). The non-colonisable barrier protects lesions from bacterial contamination, reducing the ability for secondary bacterial infections to develop and avoiding the resulting requirement for antibiotic treatment.
Orf is a highly contagious, zoonotic disease that has significant economic impacts on the UK farming industry and can compromise the welfare of affected animals.
While the disease is often self limiting, the morbidity in affected flocks, and risk of lesions progressing into serious bacterial infection or concurrent diseases such as mastitis, mean the disease can severely impact sheep flocks.
Farrow (2025) stated that a need existed for an “effective, user-friendly product to help manage orf infections”, given the difficulties in correct implementation of vaccination practices and ongoing efforts to reduce antibiotic usage in production animals.
Orf lesions with secondary bacterial infections may require treatment with systemic or aerosolised antibiotics; however, antibiotic usage related to orf could be significantly reduced by using a topical gel barrier to aid in preventing secondary bacterial infections from occurring.
Emily Collins-Wingate graduated from the University of Surrey in 2020 and has worked as a farm vet in Hampshire, Sussex and Surrey for the past five years. She has a keen interest in youngstock, flock health and the engagement of vets, students and farmers with evidence-based veterinary medicine. Emily is a member of the BVA council and sits on the VetPartners farm animal clinical board.