The relationship between equine pastern dermatitis, meteorological factors, and the skin microbiota

Equine pastern dermatitis (EPD) is a multifactorial syndrome, with prolonged exposure to moisture assumed to be a predisposing or primary factor.

To examine the course of EPD lesion severity, changes in bacterial skin microbiota, and the influence of meteorological factors.

Prospective, longitudinal cohort study over a one-year period, with six Franches-Montagnes stallions, four affected by EPD and two unaffected, that were kept under the same conditions.

Pasterns were scored for lesion severity and sampled once a month for 12 consecutive months. Lesion severity, the skin microbiota and meteorological factors were examined for associations.

EPD lesions tended to worsen in autumn and at the beginning of spring. The relationship between lesion severity and the meteorological factor precipitation was not clearly evident; high scores were preceded by both low or high rates of precipitation. Microbiota in affected pasterns appeared to have experienced a reduction in alpha diversity. Beta diversity analyses demonstrated that bacterial community structures were altered in affected versus unaffected pasterns, and that alterations were more pronounced with higher EPD scores (P = 0.005). Meteorological factors also had considerable influences on the bacterial composition, whereby these influences appeared to be more marked in the affected pasterns (P = 0.001, F = 3.19) than in unaffected ones (P = 0.005, F = 1.83).

Our study provides preliminary observations of the relationships between lesion severity, meteorological factors and cutaneous bacteria. The population was too small to draw firm conclusions, and further studies on environmental factors and the involvement of bacteria in this multifactorial disease are needed.