Contact Information

PORTUGUESE WATER DOG HEALTH ISSUES

David E. Smith, MD

Conditions|Hip Dysplasia | Addison's Disease | GM 1 Storage Disease | Progressive Retinal Atrophy|
              |Juvenile Dilated Cardiomyopathy | Inflammatory Bowel Disease | Follicular Dysplasia |

General
As a physician for more than 40 years and a Portuguese Water Dog breeder for two decades I have been fascinated and proud of the advances in our knowledge of canine diseases and particularly unique diseases of the PWD. The PWDCA, the Portuguese Water Dog Foundation (PWDF), and conscientious breeders have collaborated and assisted in the development of most of the genetic tests described below. Cheryl and I have supported these programs including the Georgie Project at the University of Utah since its inception. The observations and descriptions of disease found in the article below represent my medical interpretation of the best currently available veterinary information. I have linked other web sites and listed medical articles that are pertinent to each medical condition. The PWDCA web site has a thorough discussion on each of the medical conditions outlined below.

Because our first goal as breeders has been to produce healthy puppies with genetically good temperaments, we always emphasize the importance of parental health testing in our discussions with prospective puppy owners. This usually results in questions such as "With all this concern about genetic testing are PWDs an unhealthy breed?" Our answer has always been a resounding "No!" We explain patiently that PWDs have a small gene pool as the breed nearly died out in the late 1970s. The "founder effect" of this limited initial PWD population leads to a lower genetic variability in the breed. Geneticists have documented that low genetic variability leads to coupling of recessive genes more often. Early recognition that these recessive genes could cause significant disease led conscientious PWD breeders to perform uniform health testing on their breeding stock.

Veterinary genetic researchers realized that the small genetic homogenous population of PWDs was a treasure trove of material for research on the canine genome. Complete pedigree information was available for a number of generations of these dogs. This has led to a productive research collaboration between a forward thinking national breed club (PWDCA), willing PWD breeders and many of the nation's most foremost genome scientists. The rapid decrease in the cost of DNA PCR testing has further broadened this research. Many canine genetic abnormalities have striking similarities to human disease and many share similar abnormal genetic alleles. Elaine Ostrander at the National Human Genome Research Center at the NIH has pioneered the approach of studying canine genome abnormalities and applying these findings to human disease.

Sutter NB, Ostrander EA. Dog star rising: the canine genetic system. Nature Review Genetics. 5:900-10, 2004.

Hip Dysplasia (CHD)
Canine hip dysplasia (CHD) can occur in almost every medium and large breed. Congenital hip joint laxity causes increased stress on the joint leading to premature arthritis and pain. The inheritance of the disease appears to be caused by multiple genes (polygenetic) and nutritional/environmental factors such as rapid weight gain, excessive calcium and vitamin D intake as a puppy play a role. The Orthopedic Foundation for Animals (OFA) has provided a hip scoring system for several decades based on standardized hip x-rays. A dog must be at least 2 years of age before having official OFA rating. Preliminary hip x-rays may be submitted at 18 months but no permanent rating will be given until repeat radiographs are submitted at 24 months. Hips are scored with three grades of normal–excellent, good, fair and a borderline grade. Three grades of dysplasia are diagnosed mild, moderate and severe dysplasia. An excellent description of the full grading system is available on the OFFA web site. However anatomically normal hips are not a foolproof way to assess the genetics of the parents. OFA normal x-rays of both parents do not guarantee that a puppy will not become dysplastic but should reduce the chance to a minimum. We only breed dogs that have a normal OFA hip rating.

Fries CL and Remedios AM. The pathogenesis and diagnosis of canine hip dysplasia: a review. Can Vet J. 36: 494–502, 1995. (The full text of the article is available in PDF format for reading or download.)

Addison's Disease
Dr. Thomas Addison of Guy's Hospital London first described six human patients with adrenal gland failure in 1849. The disease of adrenal insufficiency has been named after him since that report. Acute adrenal insufficiency occurs infrequently in the PWD (1.5% of 11,384 PWDs in Chase and Lark's study at the Georgie Project, University of Utah). This exhaustive analysis suggested that there is a polygenetic basis for the disease in the PWD. Addison's also occurs in many other breeds as well as humans. There appear to be at least two distinct types present in the PWD. The most severe a polyglandular type appears to be mediated by an autoimmune response. Other endocrine glands such as the thyroid gland and pancreas are affected in this type of disease. A second type is termed atypical Addison's disease. This form of the disease is much more difficult to diagnose as the typical electrolyte abnormalities noted below are not present, and only adrenal glucocorticoid secretion is impaired.

Many veterinarians have difficulty diagnosing an Addisonian crisis as the symptoms are nonspecific and variable ranging from lethargy, low energy levels, gastrointestinal symptoms such as nausea, vomiting, diarrhea and loss of appetite, and neuromuscular symptoms such as shivering, muscle weakness and tremors. If your PWD appears ill insist on an electrolyte panel, as the classic findings of an elevated serum potassium, low serum sodium and a low sodium/potassium level (Na/K <20:1) should greatly increase the suspicion of Addison's disease. Serum cortisol levels (normal 1-4μg/dl) should be sent immediately to an outside lab and an ACTH stimulation test done to confirm the diagnosis. Both these tests should be done before corticosteroids are given as they can affect the test results. If the condition is critical, dexamethasone can be injected, as it is a steroid that does not affect the serum cortisol results. Addison's disease can be managed quite well once the diagnosis is made. Initially supplemental glucocorticoids and mineralocorticoids can be given orally daily but the best long-term treatment is an injection of Percorten-V (Novartis desoxycorticosterone pivalate DOCP) every 3-5 weeks. Once the dog is stabilized on drug therapy he/she can participate in normal activities and live a normal lifespan with periodic laboratory monitoring. No genetic tests are currently available for this disease.

Chase K, Sargan D, Miller K, Ostrander EA, Lark KG. Understanding the genetics of autoimmune disease: two loci that regulate late onset Addison's disease in Portuguese Water Dogs. Int J Immunogenet. 33:179-84, 2006.

GM 1 Storage Disease (Gangliosidoses 1)
An inborn error of metabolism first diagnosed in the PWD in the late 1980's. This recessive genetic disease causes a buildup of abnormal glycolipids primarily in the nerve tissue of the brain. The disease is caused by a deficiency of the β-galactosidase enzyme (a hydrolase enzyme) that is essential to the breakdown of β-galactosides to monosaccharides. GM-1 Storage disease is classified in the group lysosomal storage disease where the absence of a necessary enzymes leads to the abnormal accumulation of macromolecules in organs. Puppies born with the disease appear normal at birth but develop symptoms of central nervous system degeneration within a few months usually manifested by seizures and gait disturbance (ataxia). Affected puppies usually died within six months of birth. The PWDCA and NYU Neurogenetic Laboratory studied the disease and its genetics. Initially a white blood cell marker test was developed that was reported as N-95 (Normal 95% confidence level), N-99 (Normal 99% confidence level), Carrier and Affected. Since 1999 a DNA test for the gene responsible for GM 1 has been available and the results are reported as Normal or Carrier. Initially 20% of PWDs carried one copy of the gene but by breeding normal-to-normal or normal to carrier the incidence of the gene has been reduced to 2% in samples supplied between 1999-2006. Since the disease is caused by a recessive gene a carrier to normal breeding can safely be done and no affected puppies will be produced.

PRA (Progressive Retinal Atrophy)
PRA is an inherited disease of the visual receptors (rods and cones) of the retina that causes late onset blindness. The more appropriate name for this condition is progressive rod-cone degeneration (prcd). The PWDCA and Dr. Gustavo Aguirre began collaborative research on the disease in the late 1980s at the University of Pennsylvania School of Veterinary Medicine. Test breedings by Dr Aguirre sponsored by the PWDCA confirmed a recessive inheritance. Initially an electroretinogram (ERG) was required to diagnose affected dogs before breeding, since the disease did not manifest itself until five to eight years of age. Dr. Aguirre then moved to Cornell University and while at the James Baker Institute developed a linkage marker for the pcrd mutant gene on canine chromosome 9. This blood test was licensed to Optigen LLC in 1999. Subsequently Optigen has developed a specific DNA test for the actual gene. The results are reported as Normal, Carrier, and Affected. The PWDCA recommends that all breeding stock be tested and only normal/normal or normal/carrier breedings be done.

JDCM (Juvenile Dilated Cardiomyopathy)
JDCM was first recognized in several families of PWDs several years ago. It is an inherited cardiac disease that is uniformly fatal and affects young dogs between eight weeks and six months of age. There are usually no symptoms prior to sudden death although a minority of the affected puppies will have decreased energy levels and shortness of breath before death. There is no known effective treatment. The mode of inheritance appears to be a recessive gene. Dr. Meg Sleeper a cardiologist from the University of Pennsylvania Veterinary School and her associates have determined the genetic locus to reside on canine chromosome 8. A blood test for satellite markers to the actual gene became available in 2008. The test is reported as 1-1 Probably Normal or 1-2 Probably Carrier. The current recommendation of the PWDCA is that at least one parent have a 1-1 Probably Normal test.

Wernera P, Raduchaa MG, Prociuka U, Sleeper MM, Van Winkle TJ, Henthorn PS. A novel locus for dilated cardiomyopathy maps to canine chromosome 8. Genomics 91: 517-521, 2008.

Inflammatory Bowel Disease(IBD)
Dogs that have recurrent diarrhea sometimes accompanied by vomiting are frequently diagnosed with inflammatory bowel disease. However there are many other causes for this constellation of gastrointestinal symptoms including protozoan, fungal, parasitic and bacterial intestinal infections. Food allergies are a major cause of canine diarrhea and some type of elimination diet is usually recommended using novel protein and carbohydrate sources the dog has not ingested in the past. Protein sources including venison, elk, kangaroo, etc are used and the carbohydrate may be sweet potato. The idea is to be certain that the small intestine is not reacting immunologically to a food allergen. True inflammatory bowel disease requires an intestinal biopsy after an elimination diet and multiple stools have been negative for ova and parasites. The biopsy is usually done endoscopically although occasionally an open biopsy is required. If IBD is confirmed by biopsy (excessive infiltration of lymphocytes and plasma cells into the intestine) then treatment is usually begun with a combination of diet, corticosteroids and then immunosuppressives. In severe cases a hydrolyzed amino acid protein source is required to achieve adequate nutrition. This canine disease resembles human regional enteritis and many of the same treatments are used in dogs with IBD. There is some evidence that certain types of diet may precipitate inflammation and we strongly recommend avoiding corn and wheat grains in feeding. Many breeds have been diagnosed with IBD so it is not specific to PWDs.

Follicular Dysplasia (Hair Loss)
PWDs may develop a structural follicular dysplasia causing hair loss usually on the trunk. This appears to be an inherited disorder. Related breeds such as the Irish Water Spaniel and Curly Coated Retriever may also develop this disease. Hair loss usually occurs before three years of age. The hairs are weak and eventually fall out leaving bald patches. The hair may regrow but each time it is progressively weaker and the hair falls out again. The regrown hairs have a distinctive reddish brown tinge. Skin biopsy of an affected area reveals no inflammation and absent hair in the hair follicles. This distinguishes follicular dysplasia from sebaceous adenitis. In any situation with canine hair loss, hypothyroidism should be ruled out before any biopsy. The disease is not life threatening but clearly affects the dog's lifestyle. No specific therapy is available. This type of hair loss should not be confused with cyclic seasonal hair loss in other breeds. In PWDs follicular dysplasia has been observed to occur only when breeding a tight curly coat to another tight curly. Follicular dysplasia has never been reported in PWDs in a wavy to wavy or wavy to curly breeding. Ideally we would like a genetic test for follicular dysplasia, but since none is available we have adopted a policy of never breeding tight curlies together and feel comfortable with this approach.

Conclusion
If you would like to discuss any health issues of your adult PWD or Dacher puppy I would be happy to advise you by phone or email. I will update this article as new information becomes available.


Created May 20, 2009

Return to top of page