International Tibetan Spaniel Working Party

In Partnership with The Tibetan Spaniel Network

Certainties About PRA in Tibetan Spaniels

The chart below illustrates the three following statements:

For the time being, the only "certainties" regarding PRA in Tibetan Spaniels are:

1. If a Tibetan Spaniel is tested Affected, its sight will deteriorate and it will eventually be blind.
2. If a Tibetan Spaniel is tested Affected, then both its parents must (at least) be Carriers i.e. the result of (carrier x carrier) or (carrier x affected) or (affected x affected) matings.
3. If a Tibetan Spaniel is tested Affected, then all its progeny will (at least) be carriers.

QUOTE   “Dr. Gustavo Aguirre, the head of PRA research at the Baker Institute of Cornell University Veterinary School, and other genetic experts advise against using any affected dog, any known carrier, or any dog with a 25% or greater probability of being a carrier in any breeding program. This is done in order to limit the spread of the defective gene, and to reduce the chance of inadvertently breeding a carrier to another carrier. Offspring of an affected parent are always carriers or affected depending on the other parent. Offspring of a known carrier have a 50% probability of being carriers if the other parent is genetically normal. Grandchildren of a known carrier have a 25% probability of being carriers. (These probabilities apply only over large numbers, and will not necessarily apply to a specific litter.) “
Reference source :  http://www.bmd.org/health/pra.html#gene