November 26, 2018

Cataract in the UK Leonberger population

Inherited cataract is typically common in purebread dogs, but a mode of inheritance for each form of cataract is typically not identified within a breed. Many forms of cataracts that are then referred to as "breed related" if they are thought to be genetically related. Before this study, no ocular condition in the Leonberger had been proved to be hereditary. The breed was chosen in the UK because it was numerically small and a significant proportion of all the dogs could be examined for cataracts.

The ocular status of the dogs was collected by examinations on 211 Leonbergers at shows and sessions organized by breeders or veterinary surgeons and by reviewing the results of examinations on 228 Leonbergers by panel memebers of the BVA/KC/ISDS. The presence of cataracts, "defined as any light scattering opacity of the lens or its capsule" was noted and classified according to their position. 

Three different data sets were used for the statistical analysis. The first data set included 211 Leonbergers and the dogs identity, age, and presence or absence of posterior polar cataract (PPC), nuclear cataract, posterior nuclear cataract (PNC), and various cataracts were recorded. The second set included 228 Leonbergers with the same things being recorded. The third data set included 1371 Leonbergers and the names and Kennel Club Registration numbers for each of their parents. The data sets could then be merged for the Leonbergers that were examined and for the dams and sires that also happened to be examined. 

Cataracts were found in 49 dogs from the first data set. A posterior polar subcapsular cataract was found in 12 dogs, 16 dogs had bilateral nuclear cataracts, 11 dogs had posterior nuclear cataracts, and a variety of lenticular opacities were found in 17 other dogs. In the second data set, 60 dogs were diagnosed with cataracts. PPC was diagnosed in 25 Leonbergers, 13 dogs were diagnosed with a nuclear cataract, and cataracts that could not be further classified were identified in the other 29 Leonbergers. 

A separate examination was done on the association between cataracts in Leonbergers and their parents. A highly significant association between posterior polar cataract (CATPP) was found between the sire and the dog. A significant association between all the different groups of cataracts was found between the offspring and the male relative, and only for this same group could an association be found between the offspring and the mother. A logsitic regression emphasized the association between the male parent and the offspring for posterior polar cataracts. It also showed a marginal association between the female parent and offspring for the group of nuclear cataracts if the male is included in the model. The likelihood that a PPC affected sire would produce offspring affected with the same disease was 6 times higher than a sire without this form of cataracts. 

Different types of cataracts were found in many of the Leonbergers. In most cases, the infliction was insignificant. Concern was raised, however, in the more severe cases with PPCs or NCs as the statistical analysis showed a signficiant association between the offspring and their parents. Care should be taken with this information as it is likely that the PPC largely influenced the results of all of the cataracts grouped together. 

 

Heinrich, Christine L., et al. “Cataract in the UK Leonberger Population.” The Canadian Journal of Chemical Engineering, Wiley-Blackwell, 25 Aug. 2006, onlinelibrary.wiley.com/doi/full/10.1111/j.1463-5224.2006.00460.x.

Reviewed by Holly Graziano, 2018.