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Frequency of Phosphofructokinase (PFK) Deficiency in English Springer Spaniels: A Longitudinal and Randomized Study

U. Giger, A. Kimmel, D.E. Overley, L.T. Schwartz, B.F. Smith, Y. Rajpurohit. Section of Medical Genetics, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA

Paper presented at the American College of Internal Veterinary Medicine conference in Seattle in May, 2000. This paper is a report of ESSFTA Foundation sponsored research.

Muscle-type phosphofructokinase (PFK) deficiency causes alkaline-induced hemolytic crises and exertional myopathy in English Springer Spaniel (ESSP) dogs and is inherited as an autosomal-recessive trait. A single base missense mutation in the PFK gene results in truncation and instability of the enzyme. A DNA test has been available for the past decade to survey ESSP dogs for PFK deficiency. In this paper, we present data on the frequency of PFK deficiency in ESSP dogs based on the results of screening tests performed at the Veterinary Hospital at the University of Pennsylvania from 1992-1999 and on the results of a randomized trial completed in 1998-1999.

The randomized trial included 692 dogs that were either active in field trials or were AKC conformation champions. All dogs were born between 1987 and 1995, had been bred at least once, and were selected randomly from AKC records. Cheek swab samples were obtained for 368 dogs (53%), and the samples were screened for the mutant PFK allele. The total frequency of carriers was 2.7%, with a higher proportion (4.0%) of carriers in the field trial group versus the conformation (1.2%) group. Pedigree analysis revealed that all of the field trial carriers were related.

Testing was also performed on blood or cheek swab samples of a non-randomized group of 575 field trial dogs between 1992 and 1999. In this group, 14.1% percent were carriers, and 6.4% were affected dogs. Thirty-seven percent of the dogs that were tested because they had suspicious clinical signs (as noted by the owner or referring veterinarian) were, in fact, affected with PFK deficiency. The frequency of carriers peaked at 19% in the period from 1995-1997 and was lowest in 1998-1999 with 8.1%. The proportion of PFK deficient dogs was highest (8%) before 1994 and was lowest (4%) in 1998-1999.

Results from the 1998-99 randomized study and from general screening during 1992-99 indicate that the frequency of affected and carrier ESSP dogs has decreased, but PFK deficiency remains a common problem in the breed. The randomized study reveals a current 2% PFK mutant allele frequency in the field trial ESSP breeding population. Based on these results, we recommend the screening of all breeding ESSP dogs and of dogs with suspicious clinical signs in order to eliminate the disease from the breed and to provide appropriate treatment of PFK-deficient dogs.