Lawrence T. Schwartz, Chair, ESSFTA Genetics & Health Committee
Dr. Urs Giger asked me to prepare this preliminary report on the PFK study. We both felt a report at the National Amateur Field Trial was most appropriate since the major share of the ESSFTA part of the funding of this study was raised two years ago at this event. The study data are now in the final phases of analysis and are being prepared for publication and presentation at scientific meetings. In order not to jeopardize eventual publication of this study, only approximate values will be given for study results but the results as presented will be informative.
PFK deficiency is an autosomal recessive inherited storage disease which causes abnormalities in red blood cells and muscle cells. Clinical signs include intermittent dark urine, anemia, fever, weakness, or muscle fatigue. It is sometimes confused with autoimmune hemolytic anemia and other acquired diseases. Dr. Giger and colleagues at the University of Pennsylvania have developed a genetic test for carrier and affected dogs. During the past decade before this study, approximately 500 dogs (a very small percentage of all registered English Springer Spaniels) had been tested for PFK deficiency finding more than 50 affected dogs.
Approximately 400 dogs were sampled for the study. Dogs were selected from the following categories, Field Male, Field Female, Conformation Male and Conformation Female. All categories were from breeding groups, dogs who had sired at least one litter and bitches who had whelped at least one litter. All groupings were developed from random samples taken from AKC records. Field dogs and bitches had all been entered in at least one field trial (excepting puppy stakes) and all Conformation dogs and bitches had conformation championships. All dogs in the study had been whelped between the years 1987-1995. Allowing for deaths, unlocatable mailing addresses, dogs who had been placed with new owners who could not be located, refusals and owners who did not respond after at least five mail contacts, the response rate was approximately 53%. All owners who agreed to participate were sent PFK sampling kits and returned their samples to Dr. Giger. Tests were performed by Astrid Kimmel and Yashoda Rajpurohit. All results for individual dogs are known only to Dr. Giger's laboratory, preserving confidentiality.
Approximately 3% of the samples submitted were found to be carriers for PFK. In human medicine, a frequency above 1% is considered to be high. Every group (Males, Females, Conformation, Field) had at least one carrier. Most of the carriers, as expected, were from the Field group but there were two Conformation carriers. Since these Champions have been bred, they represent a multiplier effect among Conformation dogs and the prevention of further spread of PFK deficient dogs through this group should be monitored through DNA testing by breeders. The need to monitor is very clear for the Field population of Springers. Although the number of carriers in the sample is relatively small, they have all been bred at least one time and the number of carriers and affecteds from these litters are still with us.
Dr. Giger also looked at the data from the non-randomized group of Springers routinely referred to his laboratory for PFK testing. Between 1995 and 1997, he found 19% of those dogs referred were carriers and 4% were affecteds. During the past year, the percentage of carriers were 7% and the affected rate was 4%. These data, with rates higher than the randomized results reported above, have a downward trend, indicated that breeders are beginning to pay attention to PFK disorder and making conscientious breeding decisions with positive results.
In summary, the study identified several carrier dogs in the breeding pool of the breed and the results indicate that carriers continue to be produced leading to the risk of affected dogs in future generations. The historical data is indicative of a decline in carriers and affecteds but shows the continued presence of the gene. Testing should be done on all Springers used for breeding by a reliable laboratory such as the Josephine Deubler Canine Genetic Disease Testing Laboratory at the University of Pennsylvania. Information about this laboratory can be found on its web site, www.vet.upenn.edu/penngen. Data on individual dogs remain confidential, but overall survey data for all English Springer Spaniels tested will be released periodically to keep breeders informed if members of the ESSFTA and other Springer breeders continue to use this laboratory for testing.
A very high number of those tested agreed to place the names of their dogs in an open registry. We have not yet decided how we are going to develop this registry but we will be publishing it regularly, possibly on the ESSFTA web page and in printed form. The registry will not be limited to dogs in the study but any tested Springer, positive or negative, is eligible to be placed in the registry. This registry will be helpful to breeders in selecting clear breeding animals.
An abstract of the study will be submitted to the American College of Veterinary Internal Medicine in December for presentation at their meetings in Seattle in May, 2000. The actual publication of the full report is anticipated next year.