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Genetic Health Testing for Shih Tzu

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Shih Tzu

Embark for Breeders offers four breed-specific genetic health tests for the Shih Tzu among the 250+ genetic health conditions for which Embark tests. Breeders can easily share breed-specific DNA test results on parents or puppies with the one-page DNA Health Summary report with Embark test results.  

Genetic health testing is an integral part of a responsible dog breeding program. When using genetic health testing, breeders need to educate themselves about concepts such as modes of inheritance, penetrance, prevalence, and phenotype for a specific variant in their breed to apply test results. Breeders also need to know which variants are causing health concerns in their breed and which health conditions currently have no genetic test available. This handy search function by breed or health condition can show breeders which DNA tests Embark provides. 

Embark DNA tests for the Shih Tzu include the following conditions. The health condition percentages based on clear, carrier, and at-risk status presented on common, rare, and very rare genetic risk factors are based on a subset of dogs within the Embark database and do not necessarily represent all dogs of this breed. While we are not able to provide specific population numbers at this time, we believe the data provided here to be sufficient to inform on current trends within the North American population of Shih Tzu. 

Common genetic health risk factors <95% clear rate

These are the most common genetic conditions based on Embark data, ranked from most to least prevalent in the Shih Tzu, with less than 95% of dogs testing clear. 

Degenerative Myelopathy, DM (SOD1A)

The dog equivalent of Amyotrophic Lateral Sclerosis, or Lou Gehrig’s disease, DM is a progressive degenerative disorder of the spinal cord. Because the nerves that control the hind limbs are the first to degenerate, the most common clinical signs are back muscle wasting and gait abnormalities. The gene is SOD1A*, and the mode of inheritance is recessive. 

* SOD1A vs SOD1B

Please note: While we test for the SOD1A variant, we do not test for the SOD1B (Bernese Mountain Dog type) variant at this time. Degenerative Myelopathy genotype results apply only to SOD1A.

  • Based on Embark-tested Shih Tzu that have opted into research, here’s a snapshot of the breed today: 69.6% of dogs tested clear; 26.9% tested as carriers; and 3.3% at risk for Degenerative Myelopathy, DM (SOD1A)

Citations:  Awano et al 2009, Shelton et al 2012, Capuccio et al 2014 

Chondrodystrophy and Intervertebral Disc Disease, CDDY/IVDD, Type I IVDD

Type I Intervertebral Disc Disease (IVDD) is a back or neck issue affecting the discs that act as cushions between vertebrae (the spine bones). With Type I IVDD, affected dogs can have an event where the disc ruptures or herniates towards the spinal cord. This pressure on the spinal cord causes neurologic signs ranging from pain to a wobbly gait to paralysis. Chondrodystrophy (CDDY) refers to the relative proportion between a dog’s legs and body, wherein the legs are shorter and the body longer. 

There are multiple different variants that can cause a markedly chondrodystrophic appearance, as observed in Dachshunds and Corgis. However, this particular variant is the only one known also to increase the risk for IVDD. The gene is ​​FGF4, and the mode of inheritance is dominant. 

Many dog breeds, due to human selection for a desired appearance (phenotype), have a high frequency of this variant in the FGF4 retrogene, meaning most or all Frenchies have at least one copy of the variant. Therefore, breeding decisions cannot be made solely based on this breed variant.

  • Based on Embark-tested Shih Tzu that have opted into research, here’s a snapshot of the breed today: 78.8% of dogs tested clear; 1.7% tested at-risk, homozygote dominant; and 19.3% at risk, heterozygote dominant for Chondrodystrophy and Intervertebral Disc Disease, CDDY/IVDD, Type I IVDD 

Citations: Brown et al 2017 Batcher et al 2019

Prekallikrein Deficiency (KLKB1 Exon 8)

Prekallikrein is an enzyme necessary for the activation of certain clotting proteins. Fortunately, this is a benign blood disorder and is not associated with increased bleeding tendencies. The gene is KLKB1 Exon 8. The mode of inheritance is recessive. 

  • Based on Embark-tested Shih Tzu that have opted into research, here’s a snapshot of the breed today: 81.5% of dogs tested clear; 17% tested as carriers; and 1.4% at risk for Prekallikrein Deficiency (KLKB1 Exon 8)

Citations: Okawa et al 2011

 

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Very rare genetic health risk factors >99% clear rate

The following genetic conditions have a greater than 99% clear rate and are considered very rare genetic diseases in the Shih Tzu

Congenital Dyshormonogenic Hypothyroidism with Goiter (SLC5A5, Shih Tzu Variant)

Congenital primary hypothyroidism (CH) is attributed to abnormal development (dysgenesis) of the thyroid gland (e.g. agenesis, hypoplasia, and ectopia) or in rare cases by improper thyroid hormone synthesis, also called dyshormonogenesis (CDH). Inactivating mutations in the SLC5A5 gene produce an iodide transport defect which may be associated with goiters. The gene is SLC5A5. The mode of inheritance is recessive. 

Citations: Soler Arias et al 2018

With four known conditions in the Shih Tzu, this is evidence that genetic disorders are of concern within the breed, and other conditions are likely to be identified in the future. By DNA testing your Shih Tzu with Embark, you can help accelerate more novel discoveries to help your breed and all dogs. 

Canine Health and Breed Resources 

American Shih Tzu Club

Orthopedic Foundation for Animals (OFA)

OFA Canine Health Information Center (CHIC)

OFA-CHIC Health Testing Requirements for the Shih Tzu 

Mandatory

ACVO Eye Exam 

Patellar Luxation 

Optional but recommended 

Hip Dysplasia 

Cardiac Evaluation 

Remember, genetic health testing is not a diagnosis of a disease. Please consult your veterinarian for any health issues with your dog. To start your DNA testing journey, explore Embark for Breeders Dog DNA Tests. 

Lisa Peterson Contributor

Award-winning writer, journalist, and podcast host Lisa Peterson is a canine subject matter expert and Content Strategy Lead at Embark Veterinary. She served as the American Kennel Club director of communications and club communications for 10 years before becoming a Westminster Kennel Club public relations consultant from 2016 to 2021. Lisa began owning, breeding, and handling Norwegian Elkhounds more than 35 years ago, and today is an AKC judge and AKC Breeder of Merit.

Read more about Lisa Peterson

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