Explanation of Elective Tests

In addition to the required tests, at least 2 of the “elective tests” are required for CHIC status.

vWD is a potentially serious bleeding disorder and one that can be kept from being a major problem in the breed by having this one-time DNA test done. According to the VetGen website , the incidence of vWD in Shelties as of July, 2008 is: Clear – 90.3%, Carrier – 9.4%, Affected – 0.3%. Dogs “Clear By Parentage” (first generation - see OFA website for detailed policy) would be accepted into the CHIC program. The test can be performed using DNA from cheek brush collection that can be mailed-in by the owner.

This DNA test identifies dogs that are sensitive to several medications. Shelties, Collies, Australian Shepherds, and Border Collies are a few of the breeds with this genetic mutation. Several commonly used drugs, ex. antiparasitic drugs (some used in heartworm preventatives), tranquilizers (acepromazine), and anti-diarrheal drugs (Imodium®) are a few of the drugs that may affect dogs with this genetic mutation. This test would provide useful, practical knowledge for every Sheltie owner since knowing the status of each dog as clear, carrier, or affected would help a veterinarian determine which drugs to use or avoid in a particular dog. Heterozygous dogs (carriers) exhibit sensitivity to drugs that is similar to or less than that of homozygous (affected) dogs. The frequency of the mutation for Shelties and several other breeds tested at Washington State University can be found at: https://vcpl.vetmed.wsu.edu/affected-breeds. A complete list of drugs that may affect dogs with the MDR1 gene can be found at the following link: http://vcpl.vetmed.wsu.edu/problem-drugs . More information on the topic can be found at: http://vcpl.vetmed.wsu.edu/ . The test can be performed using DNA from cheek brush collection that can be mailed-in by the owner and is offered by multiple DNA testing laboratories.

Autoimmune thyroiditis may lead to hypothyroidism. It is generally assumed that autoimmune thyroiditis is inherited.

Thyroid test results done at OFA approved laboratories are listed in the statistics section of the OFA website. Shelties are listed in the top 10 of the 119 breeds having at least 50 evaluations from January 1974 forward.  From the OFA website, “Since the majority of affected dogs will have autoantibodies by 4 years of age, annual testing for the first 4 years is recommended. After that, testing every other year should suffice. Unfortunately, a negative result at any one time will not guarantee that the dog will not develop thyroiditis.” A blood sample is needed for this test. More information on autoimmune thyroiditis can be found at the following link: https://www.ofa.org/diseases/other-diseases/hypothyroidism.

CEA is a recessively inherited ocular anomaly that affects development of a portion of the eye. Homozygous recessive dogs may have lesions ranging from mild to severe. Heterozygous dogs will be phenotypically normal. Choroidal hypoplasia, coloboma, and retinal detachment are features of the disease. It occurs in Shetland Sheepdogs as well as other herding breeds. The CEA DNA test can distinguish between normal, carrier, and affected dogs. Unlike an eye examination, it is indifferent to the age of the dog or the presence of the merle gene. The ASSA Research Advisory Committee encourages breeders to consider this test for their breeding stock to keep the incidence of this problem as low as possible. This test is for CEA only, so eye examinations must still be performed to rule out other types of hereditary eye disease.

Eye examination numbers may underestimate the prevalence of the CEA mutation, because of the difficulty of detecting the defect in older dogs and the difficulty in diagnosing in a merled dog. Although the incidence of CEA in American Shelties is relatively low, it occurs in European Shetland Sheepdogs in a significantly greater frequency. For this reason, it is recommended that, at the very least, imported Shelties be tested for the CEA gene. Dogs “Clear By Parentage” (first generation - see OFA website for detailed policy) would be accepted into the CHIC program.

Of breeds having 100 or more elbow evaluations, Shetland Sheepdogs are near the bottom of the list of the more than 150 breeds diagnosed with elbow dysplasia.. More information about elbow dysplasia can be found at the following link: https://www.ofa.org/diseases/elbow-dysplasia . Radiographs (x-rays) are required for this test and it is recommended that it be done when the hips are radiographed.

Dermatomyositis (DMS) is an autoimmune disease of the skin and muscle that occurs in both humans and dogs and is caused by a combination of environmental and genetic factors. In dogs, DMS is most often diagnosed in Shetland Sheepdogs and Collies. Skin lesions consist of hair loss and crusts on areas with minimal muscle overlying the bone such as the face, ear tips, legs and feet, and the tip of the tail.

The Clark Laboratory at Clemson University (http://www.clemsoncaninegenetics.com/ ) developed a 3-gene DNA test for DMS in Shetland Sheepdogs and Collies that became available in 2017. The test will help determine the likelihood of an individual dog developing DMS and help breeders avoid producing puppies with high risk genotypes [1].

This test is different from many DNA tests as 3 genes are considered together to give a probability of low, moderate, or high risk for each dog tested to develop DMS. It does not yield a clear, carrier, or affected report. The genotype reported can be used to guide breeding decisions and assess risk of various genotypes occurring in offspring of a mating pair. To find a list of laboratories that are approved by OFA to run the DMS test see: https://www.ofa.org/diseases/dna-tested-diseases/all-dna-tests. When at that link, click on “Disease” and choose Dermatomyositis, the click on “Breed” and select Shetland Sheepdog. DMS test results from the laboratories on that list will be accepted by OFA into their database.

Only a dog’s genotype (and not the associated risk) will appear in the OFA database since, for breeding purposes, knowing the genotype is needed to make breeding decisions. The goal is to use the genetic information wisely, not to reflexively shun a dog with a high-risk genotype or to continue to breed dogs with unknown genotypes.

To learn more about DMS, the test and how to use it, go to the following link: https://americanshetlandsheepdogassociation.org/dermatomyositis/

[1] Evans JM, Noorai RE, Tsai KL, Starr-Moss AN, Hill CM, Anderson KJ, et al. (2017) Beyond the MHC: A canine model of dermatomyositis shows a complex pattern of genetic risk involving novel loci. PLoS Genet 13(2): e1006604. doi:10.1371/journal.pgen.1006604. http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1006604#abstract1