Rabbit conformational predispositions to ear abnormalities: field study of a pedigree population

Lop-eared conformation has previously been associated with rabbit ear disease in retrospective studies of clinical populations. Here, we investigated conformational and signalment risk factors for ear abnormalities in a field study of pedigree rabbits, where ear and skull conformation could be directly observed. Ears of 435 breeder-volunteered rabbits were examined with an otoscope at British Rabbit Council shows and studs, and risk factor analysis was performed with linear and binary logistic modelling. Inter-observer reliability was Substantial-Excellent for most variables. Lop-eared rabbits had increased scores and odds for 9/11 ear abnormalities tested compared to erect-eared rabbits, including abnormal ear canal colour (P<0.001), ear canal stenosis (P<0.001), multiple types of aural discharge (all P≤0.035), and behavioural reactivity to ear examination (P=0.050). More brachycephalic rabbits had higher scores for ear canal stenosis (P=0.008), whilst more dolichocephalic rabbits had higher odds of diverticulum crusts (P=0.013). Heavier breeds had higher risks of some ear abnormalities, whilst other conformation and signalment risk factors showed contradictory results. Lop-eared rabbits were significantly predisposed to ear abnormalities suggestive of otitis externa, whilst brachycephaly appeared less important in the aetiology of otitis externa than sometimes thought. Rabbit breeders, owners, and veterinarians must be vigilant for ear disease signs, especially in lop-eared rabbits.