Analysis of prevalence of presumed inherited eye diseases in Entlebucher Mountain Dogs

We analyzed the prevalence of the presumed inherited eye diseases (PIED) noncongenital cataract and progressive retinal atrophy in the Entlebucher Mountain Dog for systematic environmental influences and the additive genetic variation. Multivariate linear animal models using residual maximum likelihood methods and multivariate threshold animal models using Gibbs sampling in Bayesian analyses were used to estimate variance and covariance components. Data were obtained from the kennel club for Swiss Mountain Dog breeds in Germany. PIED were recorded using the standardized protocols of the Dortmunder Kreis, the German panel of the European Eye Scheme for Diagnosis of Inherited Eye Diseases in Animals (DOK). The material included 515 Entlebucher Mountain Dogs from 344 litters at 77 different kennels. Veterinary diagnoses for PIED were from the years 1981-2001. Pedigree information was available for up to nine generations. The multivariate animal model regarded the fixed effects of sex, birth year, experience of the veterinary ophthalmologist, litter size, percentage of examined dogs per litter, inbreeding coefficient and age at examination. The common environment of the litter and the additive genetic effect of the animal were taken into account as randomly distributed effects. The heritability estimates for PIED in the Entlebucher Mountain Dog were h(2) = 0.15 +/- 0.06 (noncongenital cataract), and h(2) = 0.34 +/- 0.08 (progressive retinal atrophy) in the linear model and h(2) = 0.32 +/- 0.05 (noncongenital cataract) and h(2) = 0.59 +/- 0.03 (progessive retinal atrophy) in the threshold model. The additive genetic correlation between noncongenital cataract and progressive retinal atrophy was moderately positive (r(g) = 0.54 +/- 0.08) in the threshold model. The number of examinations performed by the veterinary ophthalmologists was associated with slightly higher heritabilities for noncongenital cataract and considerably higher heritabilities for progressive retinal atrophy. The investigated PIED in the Entlebucher Mountain Dog are genetically influenced and the size of the genetic parameters estimated may be sensitive to the accuracy of the diagnosis and how the data were collected.