Recurrent Airway Obstruction - Is it in the Genes?

Recurrent airway obstruction (RAO) is indeed ‘in the genes’. In contrast to simple genetic disorders of the horse (e.g. ‘lethal white foal syndrome’), however, RAO is a complex disease caused by interactions of environmental and different genetic factors.

RAO is a heritable disease
Family histories and familial aggregation suggestive of a genetic basis of RAO have been reported for over 70 years (Schaeper 1939; Koch 1957). In the 1990s, it was demonstrated in Warmbloods and Lipizzans that the relative risk of developing RAO was significantly increased more than 3-fold in offspring from an affected dam or sire and almost 5-fold when both parents are affected. Parent, age and stable environment had significant additive effects (Gerber 1989; Marti et al. 1991). More recently, Ramseyer et al. (2007) found that the RAO-risk of offspring by affected sires was 4- to 5.5-fold increased, while hay feeding was the dominant environmental factor. Segregation analyses clearly revealed the presence of major genes for RAO, with an autosomal dominant mode of inheritance in one investigated family and autosomal recessive inheritance in the other family (Gerber et al. 2009). Furthermore, we also found that the ability to mount a high IgE-response is also influenced by genetic factors in the horse and differs between RAO – high- prevalence families (Scharrenberg et al. 2010). In contrast, the clinical characteristics of RAO completely agreed between the examined families (Laumen et al. 2010). [...]