| Progressive Retinal Atrophy in Chesapeake Bay Retrievers |
This article copied from American Chesapeake Club's Health Page.
WHAT IS PRA?
PRA stand for Progressive Retinal Atrophy, an inherited eye disease found
in Chesapeakes and in many other breeds. Chesapeakes have the form of
PRA called "progressive rod-cone degeneration." It has a late onset,
generally appearing in dogs between the ages of four and seven.
The first symptom of PRA is night blindness, due to the fact that the rod cells,
which let the animal see in reduced light, degenerate before the cone cells,
which are used for vision in good light.
Dogs developing PRA may bump into things in a dim room, or be hesitant
going outdoors at night. Gradually the dog will become completely blind,
even in good light.
Veterinary ophthalmologists can usually diagnose PRA before a dog’s
owner is aware that the condition is developing. This is why it is imperative
that breeding stock be checked annually by an eye specialist until age eight
or nine. Since the type of PRA in Chesapeakes is of late onset, an eye
clearance at age two, or three, or five does not guarantee that the dog is free
of PRA.
PRA in Chesapeakes is inherited by an autosomal recessive gene. In order
for a dog to be affected with PRA, he must inherit the causative gene from
both of his parents. If a puppy inherits the gene causing PRA from only one
parent, he will not have the disease, but will be a carrier with the ability to
pass this gene on to his offspring, even though he doesn’t exhibit the
disease himself. In this way the PRA gene made be "hidden" for
generations, until two dogs which carry the gene are bred together and
produce PRA affected offspring.
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