How The Seeing Eye Used a Three-Pronged Approach to Reduce the Incidence of Puppies Born Affected With PRA.

Abstract

In 1992, a four-year-old Labrador Retriever working as a guide was diagnosed with progressive retinal atrophy (PRA). A few weeks later, this dog’s sister, who was in the breeding colony, was also diagnosed as affected. These two dogs, both born in 1988, were the first of 35 confirmed cases ultimately produced from The Seeing Eye breeding colony, the last of which was born in 1997. To manage and then eliminate this autosomal recessive gene from the breeding colony, The Seeing Eye used a three-pronged approach. First, progeny testing was used early-on to identify any carriers among the breeding stock. Second, a computer program was written to calculate the probability that a young puppy was a heterozygous carrier of PRA, based on all the available evidence accumulated in the database. These calculated probabilities were used to help decide which dogs and bitches were kept for breeding. Third, a research program was funded to develop a DNA based genetic marker test that would ultimately classify each dog’s genotype as normal, heterozygous carrier, or affected.