The Portuguese Water Dog is generally considered a healthy and long-lived breed. As with any breed, however, there are certain diseases and genetic predispositions whose occurrence can be monitored and, in some cases, significantly reduced through the careful selection of parents. Health screening, genetic testing and the selection of a suitable breeding pair with a low coefficient of inbreeding are therefore important parts of responsible breeding.
HD – Hip Dysplasia
Hip dysplasia is a developmental condition in which the hip joint does not form correctly. It may cause stiffness, pain, lameness and difficulty with movement. In severe cases, it can lead to significant loss of mobility and may require surgical treatment. It is assessed by X-ray, ideally performed by a veterinary orthopaedic specialist experienced in the evaluation of hip dysplasia.
ED – Elbow Dysplasia
Elbow dysplasia encompasses developmental abnormalities of the elbow joint. It may cause pain, lameness and restricted movement and can gradually lead to osteoarthritis. It is assessed by X-ray, ideally performed by a veterinary orthopaedic specialist experienced in the evaluation of elbow dysplasia.
GM1 Gangliosidosis
GM1 gangliosidosis is a serious inherited neurological disease. It causes progressive damage to the nervous system and may result in poor coordination, tremors and muscle weakness, eventually leading to severe neurological impairment. It is tested by DNA analysis using a blood sample at the Genomia laboratory.
prcd-PRA
prcd-PRA is an inherited degenerative disease of the retina. The first sign is often reduced vision in low light, followed by deterioration of daytime vision. The disease may gradually progress to complete blindness. It is tested by DNA analysis using a blood sample at the Genomia laboratory.
EOPRA
EOPRA is an inherited degenerative retinal disease with an earlier age of onset. It causes progressive deterioration of vision and may eventually lead to complete blindness. It is tested by DNA analysis using a blood sample at the Genomia laboratory.
CDPA
CDPA is a genetically determined disorder of bone development. It may result in disproportionately shortened limbs and altered body proportions. It is tested by DNA analysis using a blood sample at the Genomia laboratory.
CDDY / IVDD
CDDY is a genetic variant associated with premature degeneration of the intervertebral discs and an increased risk of intervertebral disc disease (IVDD). It may cause spinal pain and mobility problems and, in severe cases, neurological impairment or paralysis. It is tested by DNA analysis using a blood sample at the Genomia laboratory.
Improper Coat
Improper Coat is not a disease, but a genetically determined coat type that is atypical for the Portuguese Water Dog. It may present as shorter hair on the head, face and limbs, a lack of the breed's typical facial furnishings, a flatter coat, the presence of an undercoat and shedding. It is tested by DNA analysis using a blood sample at the Genomia laboratory.
JDCM
JDCM is a serious inherited disease of the heart muscle that affects young Portuguese Water Dogs. It may cause weakness, breathing difficulties, abnormal heart rhythms or collapse and can lead to heart failure or sudden death. It is tested by DNA analysis using an oral swab collected by a veterinarian and analysed at the University of Pennsylvania in the USA (PennGen Laboratories).
MOS
MOS is an inherited syndrome associated with abnormal eye development. It may result in abnormally small eyes and other developmental abnormalities of the eye that can cause impaired vision. It is tested by DNA analysis using a blood sample at the University of Pennsylvania in the USA (PennGen Laboratories).
Comprehensive Eye Examination
A comprehensive eye examination is used to detect eye abnormalities and diseases that are not covered by genetic testing. DNA tests for prcd-PRA and EOPRA therefore do not replace a clinical eye examination. The examination is performed by a veterinary ophthalmologist.
Cardiac Examination
A cardiac examination is used to assess the heart and detect cardiac conditions that cannot be ruled out by the JDCM genetic test alone. The examination is performed by a veterinary cardiologist.
Supporting Breed Health Research
As part of Dory's testing at the University of Pennsylvania in the USA, we also participated in research into the health of Portuguese Water Dogs. We provided her DNA and health information for further scientific research focused on genetics, inherited diseases and the overall health of the breed.
What the 2025 Health Survey Revealed
The extensive 2025 Portuguese Water Dog Health Survey included data on 3,345 dogs. Overall, the results describe the breed as healthy, active and long-lived. More than half of all recorded deaths occurred at 10 years of age or older; the median age at death was 10.8 years for males and 11.4 years for females.
Historically significant inherited diseases in the breed, including JDCM, PRA and microphthalmia, were reported at very low rates. The authors of the survey associate this finding, in part, with the success of long-term genetic testing and breed health programmes.
Skin and allergy-related conditions were among the more commonly reported health problems. At least one skin or coat condition was reported in 48.9% of dogs. Frequently reported conditions included lipomas (18.2%), atopic allergies (15.1%), sebaceous cysts (14.6%) and food allergies (14.1%).
Regarding orthopaedic conditions, 84.95% of dogs had no diagnosed bone or musculoskeletal disorder. Arthritis was reported in 7.23%, hip dysplasia in 3.47% and cruciate ligament injury in 2.68% of dogs. The reported prevalence of hip dysplasia decreased from 6.9% in the 2005 survey to approximately 3.5% in 2025.
No diagnosed eye disease was reported in 87.59% of the dogs surveyed. Cataracts were the most commonly reported eye condition (7.4%), while PRA was reported in only approximately 0.2% of dogs.
Cancer was the leading reported cause of death, accounting for 56.1% of recorded causes of death. Among all dogs included in the survey, 20.3% had at least one reported cancer diagnosis. Hemangiosarcoma was the most frequently reported cancer (7.1%), followed by lymphoma (2.9%) and mast cell tumours (2.3%).
The survey also shows that the health problems currently seen more frequently in the population are not necessarily those for which simple genetic tests are available. Responsible breeding therefore cannot be based on DNA test results alone. A comprehensive assessment of a dog's health, health screening, pedigree and the suitability of a planned mating is essential.
When choosing a puppy, prospective owners often ask about the health screening and genetic testing of its parents. These are extremely important, but they represent only one part of the information that should be considered when planning a litter.
The degree of relatedness between the parents is also important. This can be assessed using the Coefficient of Inbreeding (COI), which helps quantify the genetic risk associated with common ancestors in the pedigrees of the parents of a future litter.
By the beginning of the 20th century, animal breeders already knew that mating related individuals could produce more uniform offspring with more predictable traits. They also discovered, however, that this could lead to reduced vitality, physical strength and resilience. Fertility declined, offspring were smaller, early mortality increased and lifespan was reduced. The greater the degree of inbreeding, the more pronounced these negative effects became.
Experience from the History of the Portuguese Water Dog
Dr Vasco Bensaude, who played a crucial role in saving the Portuguese Water Dog, also encountered the negative consequences of inbreeding in practice. Although he selected only the best individuals for further breeding, his dogs gradually lost reproductive ability, typical breed characteristics, working ability and health. The negative effects of the narrow genetic base were only reversed after new, unrelated individuals were found and introduced into the breeding population, thereby broadening the genetic base of the breed.
What Does COI Actually Tell Us?
Both the potential benefits and risks of inbreeding arise from the fact that related individuals share a greater proportion of their genetic information.
Put simply, if the sire and dam of a puppy share a common ancestor, they may both have inherited the same genetic information from that ancestor. Their puppy may then inherit the same genetic information through both sides of its pedigree.
This can be advantageous when particular desirable characteristics are being preserved within a breed. However, the same process may also bring together two copies of undesirable genetic traits or hidden genetic defects.
This is why the Coefficient of Inbreeding was developed. It provides a numerical estimate of the degree of relatedness within a planned mating and the genetic risk associated with it.
What Is a “Good” COI and When Is It Too High?
The original purpose of COI was to provide a numerical value that would make it easier to assess the potential benefits of inbreeding while also considering the likelihood of undesirable effects.
From a health perspective, a COI below 5% is therefore the most favourable. Above this level, the risks associated with inbreeding begin to increase.
A COI between 5% and 10% represents a higher degree of relatedness and a corresponding increase in the risk of undesirable effects in the offspring.
With a COI above 10%, the degree of relatedness is already considerable and its effects may be significant not only for the individual litter but, if similar matings are repeatedly used, also for the genetic diversity of the breed as a whole.
COI is not a diagnosis, nor does it guarantee that a particular dog will either be healthy or develop a disease. It is a value that helps express the level of genetic risk associated with the relatedness of the parents.
If the Parents Have All Available Health Tests, Why Does COI Still Matter?
Because genetic testing and COI provide two different kinds of information.
For a genetic disease caused by a single known recessive mutation, DNA testing can identify whether a dog carries that mutation. If two carriers of the same recessive mutation are bred together, each puppy has a 25% probability of inheriting the mutation from both parents and therefore being affected by the disease.
Genetic testing allows such high-risk combinations to be avoided.
Every dog, however, carries many other genetic variants that we may know nothing about. If a dog carries only one copy of a particular hidden genetic defect, it may never show any sign of it.
If two related dogs carry the same hidden defect and a puppy inherits it from both parents, however, the problem may become apparent.
Many such genetic changes may not individually cause a specifically named disease. The accumulation of their negative effects, however, can contribute to reduced vitality and resilience, impaired reproductive ability and other problems associated with what is known as inbreeding depression.
Put simply, a genetic test provides information about a specific known genetic defect for which a test exists. COI helps us assess the broader risk associated with how closely related the parents are.
DNA Tests Cannot Detect Everything
Genetic testing is extremely important, but it cannot be the only criterion used when assessing a planned litter.
There are many more recessive genetic variants than those for which genetic tests are currently available.
Parents may therefore have excellent results for every available genetic test and still both carry the same hidden genetic defects for which no test currently exists.
This is why it makes sense to consider the degree of relatedness between the parents alongside genetic testing.
COI is not a measure of the health of an individual dog. It is a measure of the genetic risk associated with relatedness.
Why Does the Number of Pedigree Generations Matter?
When calculating COI, the number of pedigree generations included is very important.
If a common ancestor appears only in a more distant generation, a calculation based solely on parents, grandparents or just a few additional generations may fail to identify that ancestor at all.
Imagine two dogs whose pedigrees appear unrelated when only the first few generations are considered. Looking further back, however, may reveal that the same ancestors appear repeatedly on both sides of the pedigree.
The fewer generations included in the calculation, the more favourable – or lower – the resulting COI may appear. However, it may not adequately reflect the true degree of relatedness.
For this reason, when evaluating our dogs and planned matings, we examine pedigrees going back at least eight generations.
Can COI Help Reduce Genetic Risk in Puppies?
Yes. This is one of the main reasons why COI is worth considering when planning a litter.
It allows the degree of relatedness between the parents to be assessed before a mating takes place and helps avoid unnecessarily high genetic risk.
COI should not, however, be considered in isolation. It forms one part of the overall picture alongside health screening, DNA testing, family health history, temperament, working ability and other characteristics of the parents.
What If the Breed Is Already Highly Related?
Purebred dog breeds are closed populations. This means that all dogs within a breed descend from a limited number of ancestors, and over generations some of those ancestors repeatedly appear in pedigrees.
In some breeds, the average degree of relatedness may therefore already be high.
A gradual loss of genetic diversity may be associated with an increased occurrence of genetic problems, reduced fertility, smaller litters, higher puppy mortality and other health problems, including allergies and congenital abnormalities.
To help preserve the health of a breed, it is therefore important to make the best possible use of the genetic diversity that still exists within the population. This may include choosing parents from less closely related lines rather than repeatedly using the same closely interconnected pedigrees.
A Dog from Another Country Is Not Necessarily Genetically Unrelated
Geographical distance does not automatically mean low genetic relatedness.
A dog from another country or a different breeding line may still share ancestors with the other parent of a planned litter when the pedigree is examined several generations back.
It is therefore not enough to assume that a dog from another country automatically represents an unrelated mating. The actual degree of relatedness can only be assessed by comparing pedigrees and calculating COI using a sufficient number of generations.
What Does This Mean for a Prospective Puppy Owner?
When choosing a puppy, it therefore makes sense to ask not only which health and genetic tests its parents have undergone, but also why those particular parents were selected and how closely related they are.
Excellent health results in the parents are extremely important. On their own, however, they cannot identify every possible genetic risk in a future litter.
Responsible breeding therefore involves several factors at the same time – health screening, available genetic testing, knowledge of pedigrees and family health history, and assessment of the degree of relatedness between the parents.
COI helps us understand that final part – how genetically related the parents of a puppy are and what level of risk may arise from that relatedness.