CVS Equine practices conduct collaborative Equine Pastern Dermatitis study
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Results could inform how to better manage and treat these common cases

CVS Equine practices have undertaken a collaborative clinical study to gather information about the clinical presentation of Equine Pastern Dermatitis (EPD), identify relevant risk factors, build knowledge of its aetiology, determine causative bacterial organisms, and outline the antimicrobial resistance profiles of horses with the condition.

It is expected that the results will help inform equine clinicians and owners how they can better treat and manage these cases in the future.

EPD (also known as “mud fever”) is a common skin disease of the lower limbs that can have several different underlying causes, including bacterial infection, parasite (mite) infestation, fungal infection (ringworm) as well as inflammation of the blood vessels in the skin (vasculitis). The disease can prove difficult to treat.

It is often associated with chronic wetting of the skin of the lower limbs from rain and mud. Cases tend to occur more often in winter and on white rather than pigmented limbs. The most frequent clinical signs include redness of the skin, hair loss, crusting and oozing of serum. The lesions are painful, and some horses may show lameness on the affected limb(s).

Despite being a common disease, very little research has been undertaken into EPD in the UK. In addition, numerous different treatments are currently used for EPD, for which there is not always robust scientific evidence.

Involving 12 CVS Equine practices[i], starting in 2022 and continuing into early 2024, samples were collected from 76 cases from horses diagnosed with EPD across the UK.

Full blood profiles were assessed, along with bacterial culture analysis of the lesions, PCR[ii] analysis for dermatophytes (ringworm fungi), microscopy for ectoparasites (mites) and skin cytology. An owner questionnaire was also completed to gather information on EDP clinical presentations and management, with supporting photographs taken. Each horse’s lesions were graded and descriptive data relating to the lesions was recorded[iii].

Data analysis was then performed to characterise EDP presentation, common contaminants and to identify the risk factors for increased severity. Culture and susceptibility data was also scrutinised to characterise commonly occurring bacteria and identify equine resistance group profiles.

The research results found that hindlimbs were most affected (n = 58; 76.3%), with lesions most commonly located in the pastern region. Clinical signs included erythema, scaling, localised oedema and pruritus.

Lesion samples identified minimal evidence of dermatophyte involvement (n = 1; 1.3%%) or ectoparasitism (n =2; 2.6%). Collectively, 185 bacterial colonies originated from the 76 samples. Testing identified 40 bacterial species across the sample population, with Streptococcus dysgalactiae (29/76 samples; 38.2%), Staphylococcus aureus (n = 21; 27.6%) and Escherichia coli (n = 13; 17.1%) most prevalent.

Penicillin was the antimicrobial agent to which the greatest frequency of resistance was identified, with less than half (n=85/185 colonies (45.9%)) of cultured organisms demonstrating susceptibility. Oxytetracycline resistance was present in 35.1% of colonies and TMPS resistance in 20.5%.

Charlotte Sinclair, CVS Equine Development Lead, said:

Equine pastern dermatitis is such a common disease of horses and ponies in the UK. And with wetter weather becoming more prevalent, it’s only expected to increase. We want to be able to offer the best treatment and management advice for horses suffering this condition. But research into this condition has been sparse and the evidence-base for the range of treatments offered has been similarly lacking. Our analysis of 76 cases over two years has highlighted the multifaceted nature of EPD - both in terms of its clinical presentation and severity and its potential aetiologies. Our results show several commonly implicated organisms, however further research is required to determine their clinical significance to EPD. We really hope that our work will lead to significant improvements in treatment and preventative healthcare for horses prone to this painful disease. The information this study provides on resistance patterns may help to guide antimicrobial use when treating these cases, to help improve antimicrobial stewardship.
CVS Group operates across small animal, farm animal, equine and laboratories, with over 500 veterinary practices, referral centres and sites in the UK and Australia. In the last five years the company has invested nearly £80 million in its sites, facilities and equipment, in addition to industry leading training and support, to give the best possible care to animals.
[i] Wessex Equine Veterinary Practice, B&W Equine Group, Corner House Vets, Endell Equine Hospital, Bell Equine Veterinary Clinic, Seadown Vets, South Wales Equine Vets, Severn Edge Vets, Animed Equine Veterinary Clinic, Alnorthumbria Veterinary Group and Oaklands Equine Hospital.
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[ii] Polymerase Chain Reaction
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[iii] As described by Sangiorgio et al. (2021).
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