Heritability of distichiasis in Havanese dogs in Norway

Abstract

Plain English summary: prevalence and heritability of distichiasis in a population of Havanese Dogs Distichiasis is an eye condition, characterized by misplaced eyelashes, that is frequently seen in dogs. Some dog breeds appear to be more at risk than others. The degree of clinical signs in affected dogs varies a lot. Many mild cases appear to be completely asymptomatic, while others suffer pain and damage to the eye, which necessitates removal of the hairs. In this study, we investigate both how common distichiasis is in the Havanese dog breed and estimate the degree of genetic influence on the trait. We find that 14.5% of eye screened Havanese, registered in the Norwegian Kennel Club, are affected with distichiasis. Most cases are graded “mild”. There is no significant difference in how many males and females are affected. We find high heritability estimates of distichiasis in Havanese (≈0.28 calculated by linear models and 0.59-0.72 calculated by Bayesian threshold models), showing a high genetic influence on the trait. The high estimated heritability mean that it should be possible to reduce the prevalence of the condition, and contribute to improved animal welfare, though systematic breeding. We recommend that all Havanese are eye screened prior to breeding, to control the prevalence of distichiasis, as well as other eye conditions that are relevant in the breed, like cataracts. Dogs with severe distichiasis or ectopic cilia should not be bred. Dogs with mild or moderate distichiasis may be bred to an unaffected partner.

Keywords

• Distichiasis
• Havanese
• Heritability
• Prevalence