The Challenge of Defining the Phenotype in Equine Airway Disease

The World Equine Airways Symposium unites clinicians and scientists interested in problems of the upper airway, such as recurrent laryngeal neuropathy (RLN) and dorsal displacement of the soft palate (DDSP), traditionally the realm of surgeons, and those interested in chronic tracheobronchial diseases including recurrent airway obstruction (RAO) and inflammatory airway disease (IAD), the realm of internists. The recent availability of the genome sequence of the horse, commercial SNP-chips and high resolution microarrays to probe the horse genome has provided both groups with powerful new tools not only to search for quantitative trait loci (QTLs) that may lead to identification of genes conferring disease risk and also provide clues to etiology of syndromes of unknown pathogenesis, such as RLN. Critical to these investigations is accurate definition of the phenotype, which is the trait or disease outcome of interest and is the detectable outward manifestation of a specific genotype. Equine respiratory diseases are not due to single gene defects but involve a complex interaction between host and environment with differences in disease susceptibility between individuals likely due to variations of several genes.