Pyruvate Dehydrogenase Deficiency is an inherited metabolic disorder affecting Sussex Spaniels. Affected dogs may present as early as 15 weeks of age with an inability to play as long as littermates. Pyruvate is an important metabolic component needed for energy production in muscle. By 1 year of age affected dogs have clinical signs of exercise intolerance including unwillingness or inability to exercise or play for more than five minutes. Affected dogs may walk slowly, sit to rest often or collapse during exercise or play. After a few minutes of rest dogs may be able to walk and play again but will tire quickly if they continue the activity. Without dietary supplementation affected dogs will die within a few years of age. High numbers of neonatal deaths have been reported in littermates of affected dogs suggesting that many affected dogs die shortly after birth.
Breed-Specific Information for the Sussex Spaniel
The Mutation of the PDP1 gene associated with pyruvate dehydrogenase deficiency has been identified in Sussex Spaniels, although its overall frequency in this breed is unknown.
Genetic testing of the PDP1 gene in Sussex Spaniels will reliably determine whether a dog is a genetic Carrier of pyruvate dehydrogenase deficiency. Pyruvate Dehydrogenase Deficiency is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the PDP1 gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Sussex Spaniels that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
Cameron JM, Maj MC, Levandovskiy V, MacKay N, Shelton GD, Robinson BH. Identification of a canine model of pyruvate dehydrogenase phosphatase 1 deficiency. Mol Genet Metab. 2007 Jan; 90(1):15-23.