Preserving the Portuguese Water Dog: The Power of Genetic Advancements

Once upon a time, the Portuguese Water Dog (PWD) was deemed the rarest breed on earth by Guinness World Records. A few years before Guinness published the rare-breed record in 1981, there were only 85 PWDs worldwide — 66 lived in the U.S. A small but mighty American fanbase was not dismayed.

Compared to 1970 when fewer than 20 PWDs worldwide were threatened with the possibility of breed extinction, the current outlook buoyed the plans of the American founders. Celebrating the breed’s new status in 1981 as a member of the American Kennel Club’s (AKC) Miscellaneous Class, they were poised to nurture Portugal’s Cão de Água on the journey to full recognition. In 1983, the PWD joined the Working Group. 

As with many newly recognized breeds, PWD enthusiasts excitedly began showing their dogs, and breeders began producing litters, though not many PWDs were around and most were on the East Coast. In 1984, there were 182 PWDs registered with the AKC.

In the mid-1980s, a perplexing neurodegenerative health condition was killing puppies. When a DNA test became available in 1989 for gangliosidosis (GM-1), breeders steered clear from crosses of carriers out of the Algarbiorum bloodline in which the GM-1 gene originated. Not using GM-1 carriers backfired when some PWDs started going blind from the progressive rod-cone degeneration form of progressive retinal atrophy (prcd-PRA).

By avoiding the Algarbiorum carriers and breeding PWDs from the Alvalade bloodline, breeders inadvertently produced dogs that developed prcd-PRA. Testing revealed that the Alvalade line carried the prcd-PRA gene, but by then the carrier frequency for prcd-PRA was 35 percent, much higher than the 6 percent carrier frequency for GM-1 had ever been.

Breeders had essentially traded one problem for another. The effect of an already small gene pool and the reduction in genetic diversity that resulted when the breed was created from two Portuguese bloodlines — Algarbiorum and Alvalade — had been further reduced.

“Most genetic disorders in dogs are controlled by recessive alleles. By increasing the frequency and homozygosity of recessive disease alleles through breeding selection, it brings their presence to light and increases their frequency,” explains Anita Oberbauer, PhD, professor at the University of California-Davis and co-author of “Review of the Current State of Genetic Testing in Dogs.”

The small, close-knit group of members of the Portuguese Water Dog Club of America (PWDCA) came together to aid researchers of GM-1 and then prcd-PRA. Some were novice dog owners, all were completely devoted to the super smart, lovable water dog.

“It was critical that we worked together,” says Maryanne B. Murray of Green Lane, Pennsylvania. “When health problems cropped up in the mid-1980s, the club and breed were flourishing. Registrations were growing steadily. We wanted only the best for the breed and were committed to preserving breed health and overall well-being.”

“People were very honest about what they had in their litters, and we worked together,” says Cathy Kalb of East Falls, Pennsylvania, who oversaw breed health concerns before PWDCA formed dedicated health committees. “There was lots and lots of communication.”

“The club’s strength was in our openness,” says Elaine Suter of Byron, Michigan. “When the researchers came to the club, people said, ‘Tell us what you need.’”

Gustavo Aguirre, VMD, PhD, DACVO, professor of medical genetics and ophthalmology at the University of Pennsylvania, led the research discovery of the prcd-PRA gene variant. “The PWD club gave us the dogs and samples we needed, and it was a truly critical effort as a few years later we found the gene. The PWD was the first breed to have a commercial test for prcd-PRA,” he says.

Other health conditions and a non-health condition known as improper coat (IC) came to light in later years. GM-1, prcd-PRA, juvenile dilated cardiomyopathy (JDCM), early-onset PRA (EO-PRA), microphthalmia, and IC were addressed candidly with a shared goal of advancing gene discovery. Formed in 1997, the Portuguese Water Dog Foundation (PWDF) has played a key role in important discoveries via the support of $1.2 million in funding for research grants that benefit the breed and other breeds as well. 

“It’s a privilege and an advantage to have these DNA tests,” Murray says. “There is no reason for a dog to be blind or have JDCM.”

Here is a look at the grassroots efforts of PWDCA club members that led to the gene variant discoveries for five health conditions and IC. The genetic tests that have resulted give breeders the tools they need to selectively breed healthy dogs not affected by these diseases.

GM-1: A Rare Storage Disease

Breeder Jane Harding of Chester, Connecticut, finished her foundation bitch, “Craca” (CH White Cap Craca JD AD), to her show championship title and then eagerly bred her. The second breeding of Craca to a beautiful male, “Bo” (CH Alfama Ubo), gave Harding eight adorable puppies.

“Six months later, I began getting calls from three owners about sick puppies or puppies that had died from a mysterious neurologic illness,” Harding says. “People thought it was parvovirus or a spinal disease.”

Harding began researching the illness and learned that puppies from New York to California were dying from similar clinical signs. Loss of coordination, muscle tremors, weight loss, and a wide gait were common. Progressively severe and fatal, most puppies died naturally or were euthanized by 1 year of age.

“It took the coordination and care of breeders to bring the research together,” says Harding, who helped researchers gather DNA samples and reach people whose dogs had produced affected puppies. 

A DNA test for the strange illness, now known as gangliosidosis (GM-1), was made available in 1990. The GM-1 gene variant discovery was made by researchers at the Eunice Kennedy Shriver National Institute of Child Health and Development, as children are susceptible to a similar inherited illness, and New York University.

A rare lysosomal storage disorder, GM-1 occurs in dogs having insufficient beta-galactosidase enzyme activity, which is responsible for breaking down specific carbohydrates in cells. These GM-1 cells accumulate in cells of the brain and nervous system. Genetic testing for the GLB1 gene variant identifies carriers that do not exhibit signs but can pass the disease on to their offspring if crossed with another carrier.

prcd:PRA: Late-Onset Blindness

Joan C. Bendure of Fairview, Pennsylvania, remembers when her PWDs, “Admiral” (CH Benhil’s the Admiral Norvic) and his half-brother, “Magellan” (CH Donamur’s Magellan of Benhil), were diagnosed with prcd-PRA. Their Portuguese-imported sire, CH Fidalgo Do Condinho, also was affected with the eye disease that leads to blindness. 

“I was the first to come forward with prcd in 1990,” says Bendure, which led to the club’s consulting Dr. Aguirre, an ophthalmologist at the University of Pennsylvania. “By now, affected dogs were turning up all over.”

“When PRA started in PWDs, we had to know if it was similar to the prcd-PRA we had been studying for six years in Miniature Poodles,” Dr. Aguirre says. “In 1998, we were close to the gene discovery. The club wanted to know what it would take to get a genetic test for prcd-PRA in PWDs. I told them, ‘Just bring us enough dogs and samples.’”

Although the eye disease can be clinically diagnosed in PWDs around 3 to 5 years of age, total blindness doesn’t occur until dogs are 7 to 8 years of age. Night blindness is the first sign of the disorder due to degeneration of rod photo­receptors in the retina. These cells take light coming into the eyes and relay it to the brain as electrical impulses that are interpreted to create images. Eventually, the cone cells, which function in daytime conditions, deteriorate and dogs become completely blind.

Dr. Aguirre and his collaborator, Dr. Gregory Acland of Cornell University, mapped the prcd-PRA gene variant in PWDs to canine chromosome 9. The DNA test for the condition allows breeders to detect unaffected carriers and recognize affected dogs before the onset of the eye disease. Importantly, it also allows breeders to test their dogs prior to breeding to avoid producing the blindness disease.

JDCM: Heart Disease in Puppies

Breeder Lisa Wiley of Bethany, Connecticut, stumbled onto the inherited heart disease juvenile dilated cardiomyopathy (JDCM) in 1997 when a litter she bred produced affected puppies. “A dog I loved was a carrier,” she says. “I bred ‘Bud’ (CH Glenllyn Windruff Budweiser) to my female, ‘Taffy’ (CH Turnabout Salt Water Taffy).”

Four female puppies out of Taffy’s litter died from JDCM. Early on called sudden puppy death, JDCM occurs in puppies from 2 weeks to 8 months of age. Affected puppies often die suddenly and unexpectedly.

Wiley and Carol Mattingley of Pottstown, Pennsylvania, breeder-owner of Bud and chair of the PWDCA Cardiac Committee, began working together to gather blood samples from carriers and their relatives for DNA analysis. They reached out to University of Pennsylvania researchers Margaret M. Sleeper, VMD, associate professor of cardiology, and Paula S. Henthorn, PhD, professor of medical genetics, who studied the genetics of JDCM with support from PWDCA and PWDF.

“The Cardiac Committee was amazing. They provided a huge pedigree and cases for us to study. Meanwhile, the club supported the research financially,” Dr. Henthorn says.

Their research attributed the disorder to a gene variant on canine chromosome 8 inherited as a fully penetrant recessive trait. This finding allowed for a genetic test to identify carriers. Describing JDCM in PWDs, they said the disorder ranges from sudden unexpected collapse and death with no preceding clinical signs to depression and reduced appetite for up to five days before dying from congestive heart failure.

“When we found the JDCM gene variant, there were DNA tests for GM-1 and prcd-PRA,” says Dr. Henthorn. “Knowing that the PWD had a small gene pool, we were careful to advise breeders to selectively breed their best dogs even if they were carriers to not lose their bloodlines. Today, it is rare to find a PWD carrier for JDCM in North America. If it occurs, it typically is a dog produced from a frozen semen breeding of an old sire.”

EO-PRA: Early-Onset Blindness

A new form of PRA showed up in PWDs around 2014. “Early-onset PRA (EO-PRA) came from young dogs that a breeder had produced by crossing PWDs imported from Portugal,” says Bendure, who teamed up again with Mattingley to find answers to an inherited eye disease affecting the breed.

Turning to ophthalmologist Dr. Aguirre for help, they and fellow club members collected DNA samples and the PWDF provided funding for whole-genome sequencing to find the gene variant. “They brought the sire and grandsire of this first affected litter to us as well as the whole litter of affected and unaffected dogs,” Dr. Aguirre says. “We were afraid the disease would become rampant in the breed.”

EO-PRA occurs in PWDs around 1 to 2 years of age and progresses quickly. Initially, affected dogs walk into objects and have difficulty following moving targets. Their condition becomes progressively worse until they are totally blind. 

Genetic analysis by Dr. Keiko Miyadera, also of the University of Pennsylvania, and Dr. Aguirre found an insertion nucleotide causing a CCDC66 frameshift variant associated with this new form of EO-PRA in PWDs. The genome study included four affected littermates, two unaffected littermates, the unaffected parents, and 15 unrelated control PWDs. The recessive disease occurs in dogs whose parents are carriers. The variant reduces the ciliary function of photoreceptors in the retina responsible for converting light signals into neural impulses that are sent to the brain to create images.

Microphthalmia: Puppy Eye Syndrome

Prior to breeding her foundation bitch, Cathy Kalb had health testing done based on the parent club’s recommendations for Orthopedic Foundation for Animals’ health certification. This included testing for hip dysplasia and an annual eye examination. In 1987, the last time Kalb bred her bitch, one puppy out of a litter of 10 developed a syndrome causing it to be unusually small and to have very small eyes. Hand-raising the puppy she named “Thumbelina,” Kalb was concerned the puppy had a disorder she had seen before. 

In 1986, Kalb and Pam Schneller of Bay Shore, New York, took a litter of 7-week-old puppies bred by Schneller to be examined by Dr. Aguirre at the University of Pennsylvania. Schneller’s litter of 10 puppies were born to normal parents, but five of the pups were blind, small and not thriving and three pups were euthanized at 2 weeks of age due to failure to thrive. Dr. Aguirre determined the other two pups also were affected.

Dr. Aguirre diagnosed ocular and metabolic abnormalities caused by the syndrome later known as microphthalmia. Affected puppies primarily had eye problems including very small eyes, glaucoma, cataracts, no pupils, and pieces of eye parts. Microphthalmia puppies were poor nursers and weak, often dying in a few days unless they were raised by hand.

“I posted frequently about the signs of this syndrome in the PWDCA’s newsletter to alert breeders about this likely inherited disease,” says Kalb, chair of the PDWCA Eye Committee. “Very few cases were reported, probably due to early deaths without diagnosis.”

A rally cry for funds to support a genetic study and for DNA samples came together in 2015. Milan Lint of New Hope, Pennsylvania, organized a matching gift fundraiser that netted $25,000. University of Pennsylvania researchers Margaret L. Casal, DVM, PhD, professor of medical genetics, reproduction and pediatrics, along with Dr. Karina Guziewicz led the discovery of the gene variant for microphthalmia in early 2020. 

Although the finding has yet to be published in a scientific journal, genetic testing for microphthalmia currently is available through the University of Pennsylvania. The ability to test breeding stock to learn their carrier status ensures no puppies will be born with the condition.

IC: Improper Coat

Most people will easily recognize a Portuguese Water Dog (PWD) whether it is curly or wavy coated or whether it is groomed in the lion or retriever clip. On the other hand, people are not as likely to recognize a PWD with an improper coat (IC).

Although there are inconsistencies in the look of dogs with the IC gene variant, they tend to have short, flat coats on the muzzle, face and head; short and sometimes sparse coats on the front of their legs, with feathering behind the legs; a full ruff on the neck; and longer, thick coat on their bodies. Unlike their hypoallergenic relatives, they shed.

IC is not a health condition, but it can be problematic. “If a PWD with IC ends up in a shelter and is not recognized, we are unable to provide rescue support,” says Joan C. Bendure of Fairlawn, Pennsylvania, who helped to pilot the discovery of the gene mutation. 

IC had been cropping up in litters for many years. Bendure eventually sought help from Gordon Lark, PhD, a geneticist at the University of Utah who had built the Georgie Project DNA database of Portuguese Water Dogs. Working with researchers at the National Institutes of Health on a multi-breed study to identify genes regulating dog coats, Dr. Lark wondered if the gene responsible for hair furnishings contributed to IC in PWDs. DNA from a dog with IC was genotyped. As Dr. Lark suspected, the dog lacked part of the DNA sequence associated with furnishings.

Together with the NIH researchers, Dr. Lark developed a DNA test in 2010 that identified the RSP02 gene variant for IC for IC, which allows breeders to use selective breeding to avoid producing PWDs with IC. The recessive condition occurs in dogs that inherit copies of the gene allele from their sire and dam. Dr. Lark believed that the gene variant was likely introduced in the PWD population in the 1970s.

PWDs born with the IC variant may participate in all sports; however, in conformation, IC is considered a flaw, though not a disqualifying fault. IC does not affect a dog’s health or longevity. Puppies born with IC are identifiable around 2 to 4 weeks of age.

A Model Breed Club for Health Research

Reflecting on the PWD genetic advances, Wiley who contributed significantly to the JDCM research, says, “In 1988, the PWDCA was a model breed club for health research. Breeders today must realize it’s OK to breed a quality carrier to a clear dog, as the puppies will be healthy. You can slowly eliminate a disease without shrinking the gene pool. It’s important to keep a bloodline going.”

Dr. Oberbauer advises, “When genetic tests are available to help select for improved health, they can be used provided the selection is applied gradually so as not to depopulate the breed. Breeders should be mindful of the ‘big picture’ and how their choices will impact the breed population. The idea is to improve the breed as a whole for future generations.”

Murray, who cared for the legendary PWD Charlie Brown after the passing of Deyanne Miller, the founder of the breed in America, says, “We have to educate new people and stay on top of health conditions that affect our dogs. Our gene pool even today is not that big.”

Small but mighty, the American PWD enthusiasts are a shining example of what can be accomplished by working together and staying honest about genetics and health conditions. No longer the rarest breed on earth, the PWD today is most certainly one of the most loved. 

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