Health testing is able to empower breeders and puppy owners with information on breeding stock genotypes (the set of genes a dog carries) and phenotypes (the dog’s observable physical characteristics – which are influenced by both its genotype and by its environment). Ultimately the goal is to enable breeders to make breeding decisions based on their program’s goals, and let puppy owners know their puppies have a reduced risk of inheriting breed-specific health problems when the parents show favorable health screening results.

Testing Phenotype

Phenotype tests involve testing a dog based on its physical characteristics, at a certain snapshot in time. When “breeder health testing” is mentioned, it usually refers to these physical exams and x-rays of a dog’s structure and joints.  Health testing is more than just a trip to the vet for a physical exam. The most prominent organization offering evaluation and recording of test results in the US is the Orthopedic Foundation for Animals (OFA) which offers a wide variety of general health and breed-specific tests.  Parent breed clubs can also work with OFA to track and provide a list of recommended minimum tests based on current issues within the breed. This allows for OFA to work with parent breed clubs to measure the progress of breeders in reducing breed-specific health concerns. 

Despite being armed with test result information, dogs are still living beings and not abstractions. By choosing more structurally sound breeding pairs, a breeder could improve their chances of producing healthier puppies. OFA performed an review of its own database based on the probability of puppies affected by elbow dysplasia (ED) given the known elbow status of their parents. They found the following mating probability results for 13,151 breeding pairs of dogs:

• Normal Elbows x Normal Elbows = 12.2% offspring affected with ED
• Normal Elbows x Dysplastic Elbows = 26.1% – 31.3% offspring affected with ED
• Dysplastic Elbows x Dysplastic Elbows = 41.5% offspring affected with ED

Applicable Tests

Below is a list of applicable tests for Kai Ken, as well as a brief description, minimum age required for permanent test recording, validity periods, and OFA recording fees for a single dog.  The costs below do not include fees for related vet examinations or genetic test kits; all tests listed below are phenotype tests except for the DNA profile test.

If tests are performed prior to the minimum test age, results recorded to OFA will be considered preliminary.  In the case of hips and elbows the best time to perform tests are when the dogs 2 years or older because joints will still be in flux until they become adults, after which they will naturally degrade over the lifetime of the dog.  While there is no official statement on this, it has been rumored that OFA will not grade an adult dog’s test higher than a score it received on a preliminary test. OFA offers discounted recording fees for litters and kennels.  A good resource for finding local upcoming health clinics (for discounted exam fees) is: https://www.cavalierhealth.org/health_clinics.htm

Exam Fees for a Single Dog

Below is an estimated average/worst/best case scenario for examination costs for a single dog with the applicable Kai Ken OFA tests. At the time of writing, all upcoming clinics available through the link above were used to provide data for the chart. The single vet example is included as a baseline for doing all health tests at a single vet. The DNA test price used is for Embark’s breeder swab with and without a discount.

Note that ‘Heart ECHO’ and ‘Hips + Elbows’ are not included in the totals at the end, because typically vets recommend doing an echocardiogram only if something turns up in the auscultation; and similarly you wouldn’t pay for a hips + elbows exam if you already paid for them separately. The following table does not including OFA recording fees.

Testing Genotype

Genotype tests have gained in awareness and public-accessibility with companies like Embark and Optimal Selection. Genetic testing involves swabbing a dog’s mouth to scrape cheek cells that will be used in DNA analysis.  Every dog inherits a unique mix of DNA from their parents – they receive 50% of their DNA from each of their parents, who received 50% of theirs from each of their parents, and so on. Dogs have a total of 78 chromosomes, of which there are 38 pairs and two sex chromosomes (39 pairs total).  Inside of each cell in a dog’s body, the DNA is bound into a unit called a chromosome.  Each chromosome contains many genes which are all tied together into a long strand of DNA. Each point on this strand of DNA is called a locus, and at each locus there are two alleles forming the gene. Different variants of genes are known as alleles; alleles come in pairs – one allele is inherited from each parent.  The list of possible alleles at each locus are called a series.

Let’s look at the A-Locus which determines the agouti coat coloration in dogs as an example. The agouti series consists of 4 alleles that follow the dominance order of: A^y (sable), a^w (agouti), a^t (tan points), and a (recessive black).  In an example of a sable parent that carries black & tan (A^ya^t) being bred to a black & tan parent (a^ta^t), the possible combinations are as follows:

The result of each combination of alleles is determined by a trait’s mode of inheritance. Some alleles are dominant, meaning that only a single copy of that allele is necessary to express the trait, notated with a capital letter.  Recessive alleles require two copies of the allele to be expressed, and are notated with a lowercase letter.  Since A^y is dominant, there only needs to be one allele to be expressed. In the chart above, the possible agouti distribution among offspring is 50% sable and 50% black and tan.

Genetic Diseases

Series dominance can also be applied to genetic diseases, where diseases that are recessive require two copies of a mutation to be expressed, known as autosomal recessive, and diseases expressed in a dominant manner only require one copy of the mutation for a dog to be at risk.  When referring to autosomal recessive genetic diseases, results are often classified as:

CLEAR: a dog contains two healthy copies of a gene sequence and is not at risk of developing the associated disease (at least due to the gene’s mutation).

CARRIER: a dog contains one healthy copy and one mutated copy of a gene sequence and is not at risk of showing clinical signs of the disease, but has a 50% chance of passing on the mutated copy to any offspring.  Testing any potential mates to a carrier is recommended to ensure puppies produced are not at risk of developing the disease.

AT RISK: a dog contains two copies of the mutated gene, will most likely show clinical signs of the disease (referred to as affected), and will only be able to pass on mutated copies of the gene to any offspring.

Using the same Punnett square above, we can calculate the probability of each puppy inheriting an autosomal recessive disease given the known genetics of their parents. In the charts below, h indicates a healthy copy of the gene, and m indicates a mutated copy of the gene.

	Clear x Clear: 100% clear
	Clear x Carrier: 50% clear, 50% carrier
	Clear x At Risk: 100% carrier
	Carrier x Carrier: 25% clear, 50% carrier, 25% at risk
	Carrier x At Risk: 50% carrier, 50% at risk
	At Risk x At Risk: 100% at risk

With genetic testing and mindfulness of the inheritance possibilities above, breeders can track and make breeding decisions to eliminate known genetic diseases from their lines.

Progressive Retinal Atrophy

Progressive retinal atrophy (PRA) includes a diverse group of canine retinal degenerations causing inherited blindness.  Some of the disease variations include early onset, late onset, autosomal recessive, dominant, and some are linked to the X-chromosome. PRA diseases affect the rod and cone type photoreceptor cells within the retina. Rods gather information about light intensity and are an important factor in night vision, while cones are responsible for distinguishing color and are major contributors to day vision.  There are two PRA diseases affecting Kai Ken at this time.

PRA-prcd

Progressive retinal Atrophy, progressive rod-cone degeneration is an autosomal recessive, late onset, inherited eye disease. This disease results in the degeneration of the rod then cone photoreceptor cells within the retina, causing night blindness and a loss in peripheral vision first, eventually progressing to daytime vision loss and typically resulting in complete blindness in most dogs.  While this disease can be detected around 1.5 years of age via veterinary eye exam, most affected dogs will not display signs of the non-painful vision loss until they are between 3 to 5 years old.  Outside of a veterinary exam, other things to look for are an increased reflectivity of the tapetum (eye shine) and observing slowly constricting pupils under a bright light, because the retina is no longer telling the pupils that too much light is entering the retina.

PRA-crd4/cord1

Progressive retinal Atrophy, cone-rod dystrophy 4, is also an autosomal recessive inherited eye disease, however the cone cells degenerate first, leading to a loss in day vision before a loss in night vision and gradually developing into complete blindness.  The age of onset varies with this slow-progressing disease, it has been reported in dogs from 6 months to 15 years of age, although the average onset age is about 5 years old.  The mutation for this disease occurs in the RPGRIP1 gene and show incomplete penetrance, meaning not all dogs with two copies of the mutation will become affected. Rather, this suggests that unknown genetic or environmental modifiers could change the disease’s progression.

Collie Eye Anomaly (CEA)

Although CEA is not known to affect any Kai Ken, it is affecting a related breed, the Hokkaido Ken.  Also known as Choroidal Hypoplasia, this hereditary congenital visual impairment can vary among affected dogs, but typically leads to vision loss due to holes or pits in different layers of the eye. Vision loss may be slight or total, and in severe cases can lead to retinal detachment.  Most commonly found in herding breeds, the mutation occurs due to a deletion on the NHEJ1 gene and can be detected in puppies as early as 5-8 weeks old, presented as a poorly developed or thinning choroid.

Why Test Both Genotype and Phenotype?

“Since I’ve done genetic testing on my dog and they are clear of PRA, is it redundant to do an OFA eye exam?”

The DNA sequence is not completely mapped, and new information continues to be discovered.  As genetic diseases are mutations of genes, it is possible for dogs to display a new mutation of the disease, which could go undetected via genetic test but be physically expressed.

Resources

• https://www.ofa.org
• http://www.doggenetics.co.uk
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6042528/
• https://www.pawprintgenetics.com
• https://www.animalgenetics.us
• https://www.pethealthnetwork.com
• https://ancestry.com