Global Frequency Analyses of Canine Progressive Rod-Cone Degeneration-Progressive Retinal Atrophy and Collie Eye...

Area of Science:

• Canine genetics
• Population genetics
• Veterinary ophthalmology

Background:

• Hundreds of canine genetic variants and commercial tests exist, but data on geographic distribution and frequency changes over time are limited.
• Progressive rod-cone degeneration-progressive retinal atrophy (prcd-PRA) and collie eye anomaly (CEA) are common inherited disorders in dogs.

Purpose of the Study:

• To analyze geographic distributions and temporal changes in allele and genotype frequencies for prcd-PRA and CEA.
• To evaluate the impact of genetic testing and breeding decisions on disease frequencies over a 15-year period.

Main Methods:

• Utilized genotype data from 86,667 dogs for the PRCD variant (prcd-PRA) and 33,834 dogs for the NHEJ1 deletion (CEA).
• Employed chi-square goodness-of-fit, time-trend graphical analysis, and regression modeling.
• Data spanned 15 years, 82 countries, and 67 breeds/breed mixes.

Main Results:

• Significant differences in genotype frequencies were observed for both prcd-PRA (p = 2.7 × 10^-152) and CEA (p = 0.023), with opposing temporal trends.
• Regression analysis indicated that time, breed, and breed popularity significantly affected the odds of dogs being homozygous or heterozygous for these diseases.
• Homozygous affected dogs, particularly for prcd-PRA, were still present 14 years after test availability.

Conclusions:

• Genetic testing has informed breeding practices, leading to a reduction in affected dogs.
• The continued presence of homozygous affected dogs suggests ongoing challenges, possibly from unknown carriers.
• Continued genetic testing of dog populations is recommended to monitor and manage inherited diseases.