HOARSI reliably identifies RAO-affected horses in our population.

SummaryEquine recurrent airway obstruction (RAO) is a chronic lower airway disease of the horse caused by hypersensitivity reactions to inhaled stable dust, including mould spores such as Aspergillus fumigatus. The goals of this study were to investigate whether total serum IgE levels and allergen-specific IgE and IgG subclasses are influenced by genetic factors and/or RAO and whether quantitative trait loci (QTL) could be identified for these parameters. The offspring of two RAO-affected sires (S1: n = 56 and S2: n = 65) were grouped by stallion and disease status, and total serum IgE levels and specific IgE, IgGa, IgGb and IgG(T) levels against recombinant Aspergillus fumigatus 7 (rAspf7) were measured by ELISA. A panel of 315 microsatellite markers covering the 31 equine autosomes were used to genotype the stallions and their offspring. A whole-genome scan using half-sib regression interval mapping was performed for each of the IgG and IgE subclasses. There was no significant effect of disease status or sire on total IgE levels, but there was a significant effect of gender and age. rAspf7-specific IgGa levels were significantly higher in RAO-affected than in healthy horses. The offspring of S1 had significantly higher rAspf7-specific IgGa and IgE levels than those of S2. Five QTLs were significant chromosome-wide (P < 0.01). QTLs for rAspf7-specific IgGa and IgE were identified on ECA 1, for rAspf7-specific IgGa and IgGb on ECA 24 and for rAspf7 IgGa on ECA 26. These results provide evidence for effects of disease status and genetics on allergen-specific IgGa and IgE.