Allergen-specific immunoglobulin-Es for dermatitis in the Japanese native Noma horses

Noma horses are native Japanese horses. Health checkups revealed that many Noma horses developed dermatitis during summer, which subsided in winter. Seasonal development and signs of itching, suggestive of allergic dermatitis, were observed. In this study, allergen-specific IgE was measured using blood samples collected from 15 Noma horses in summer and winter to identify allergens highly associated with dermatitis. The presence of dermatitis in the subject individuals was recorded during blood sample collection. White blood cell and eosinophil counts, serum total IgE concentration, and serum allergen-specific IgE units (ARUs) were measured. White blood cell and eosinophil counts were significantly higher in horses with dermatitis in summer compared to winter. On the other hand, there was no significant difference in serum total IgE concentration regardless of the presence of dermatitis or the season. Horses with dermatitis in summer showed higher ARUs derived from red ants, horseflies, biting midges, cockroaches, deerflies, and mosquitoes than those in winter. These ARUs were positively correlated with white blood cell and eosinophil counts. The factor analysis results suggested that sensitization to some insects, such as mosquitoes and deerflies, may be a cause of dermatitis. In conclusion, insect-derived allergens could be associated with the onset of dermatitis in Noma horses.