Inadvertent propagation of factor VII deficiency in a canine mucopolysaccharidosis type I research breeding colony.

Issues of cost and genetics can result in inbreeding of canine genetic disease colonies. Beagles often are used to maintain such colonies, providing stock for outcrosses. Factor VII (FVII) deficiency is a hemostatic disorder found at increased frequency in beagles and has been characterized at the DNA level. Deficiency of FVII presents obstacles in colonies founded with beagles. An initial finding of a FVII-deficient pup from a longstanding colony prompted us to evaluate FVII deficiency fully in this colony. Current and archival records and tissues were used to reconstruct the colony pedigree, assess the contribution from beagles, and test samples to document the source and frequency of the mutant FVII allele. As part of this study we developed a PCR-based diagnostic assay that was simpler than what was previously available. Pedigree analysis revealed a founder effect implicating beagles that led to high frequency (55%) of the mutant allele. In addition, affected animals were identified. The complete picture of the clinical effect within the colony remains unclear, but unusual neonatal presentations, including hemoabdomen, have occurred in pups affected with FVII deficiency. Use of a PCR-based diagnostic assay to screen all potential beagle breeding stock will prevent similar occurrences of FVII deficiency in future canine research colonies.