Leucocytoclastic vasculitis associated with Staphylococcus intermedius in the pastern of a horse

Epidemiological observations on pastern dermatitis in young horses and evaluation of essential fatty acid spot-on applications with or without phytosphingosine as prophylactic treatment

Background - Equine pastern dermatitis (EPD) is a common multifactorial clinical syndrome in horses. Treatment can be difficult; pathogenesis and triggering factors cannot always be determined. Objectives - To assess risk factors for developing EPD in a large group of horses kept under the same conditions and to analyse whether or not a spot-on containing essential fatty acids and antimicrobial agents is able to prevent the development of EPD or accelerate the healing process. Conclusion and clinical importance - Moisture and lack of pigmentation predisposed to EPD. Topical application of the tested spot-on once weekly did not prevent the disease. A positive effect of both spot-on products on the severity of EPD lesions was detected.

The influence of clinical severity and topical antimicrobial treatment on bacteriological culture and the microbiota of equine pastern dermatitis

Background

Equine pastern dermatitis (EPD) is a common dermatological problem in horses, yet its aetiology and pathogenesis are poorly understood.

Objectives

This study aimed to investigate the effects of lesion severity and topical antimicrobial treatment on bacterial flora of EPD‐affected skin.

Animals

Sixteen horses with EPD were investigated.

Methods and materials

An observational study was conducted by assigning a clinical severity score ranging from 0 (macroscopically nonlesional) to 21 (severe), and sampling the most and least severely affected limbs of 16 horses (32 limbs) for bacteriological culture and 16S rRNA sequencing. Topical antimicrobial treatment in the month before sampling was recorded. The limbs were allocated to a nonlesional or mildly affected group (Group A, score 0–3) and a moderate to severely affected group (Group B, score 4–21).

Results

The most commonly cultured bacterial species was Staphylococcus aureus (one of 15 Group A versus nine of 17 Group B). Within Group B, S. aureus was found in three of six limbs treated with topical antimicrobials and in six of 11 untreated limbs. β‐haemolytic streptococci (three of 32) and Trueperella pyogenes (two of 32) also were cultured exclusively in the untreated limbs of Group B. Staphylococci and streptococci were found more often by 16S rRNA sequencing than in culture. Limbs with higher lesion severity and topical antimicrobial treatment appeared to have a lower alpha diversity and different beta diversity compared to milder and untreated lesions.

Conclusions and clinical importance

Observed differences in microbiota of equine skin are likely to be linked to the presence and severity of EPD and topical antimicrobial treatment. Further research is needed to establish causal bacteria.