CANINE GENETICS

CHG is a fatal canine thyroid problem present in the form of a goiter at birth. 2018 stats reveal it also affects cats, sheep, goats and humans.

~ Barbara J. Andrews Jan. 2019 - Dr. Fyfe is currently with a research company.  If you missed the first part of the interview Part 2 about CHG in the Toy Fox Terrier, you should read that first. The information below was received directly from Dr. Fyfe as Part 4 of his generous contributions to our genetic knowledge of CHG, a rare but 100% fatal condition in newborn animals.

CHG 4: Cost And Testing For Congenital Hypothyroidism With Goiter

John C. Fyfe, D.V.M., Ph.D.

What is this test for? (link at bottom of page explains genetic basis & cause) The test detects the presence of the gene mutation that causes CHG in Toy Fox Terriers.  Using the test it is possible to identify TFT that are:

affected with CHG (affected individuals have two copies of the mutant gene), though the disease is obvious clinically.

 

carriers of CHG (have one copy of the mutant gene and one normal gene copy). Carriers do not develop the disease themselves but can pass the defective gene on to the next generation. If members of the next generation receive a defective gene from each parent they will develop CHG.

 

genetically unaffected for CHG (have two copies of the normal version of the gene).

How accurate is the test? The test itself identifies the actual disease-causing mutation and is therefore totally reliable in identifying this form of CHG. If, however, a second form of hypothyroidism were to develop in the breed the test would not be able to identify it. Please take every care to follow the submission instructions and ensure that the brushes are labeled correctly.

How do I submit samples for testing? To submit brush samples for this test, the following procedure should be followed carefully:

Procedure:

1. We advise that two people collect the DNA sample, one to gently restrain and hold the head, the second to collect the sample. To avoid contamination from dog food, please collect the sample at least 2 hours after the last meal or snack. Dogs may have access to water at any time.

 

2. Label each brush sleeve with the dog’s full name, AKC or UKC registration number and owner’s name. Label 2 brush sleeves per dog. Label on the paper side of the brush sleeve (labels on the plastic side come off too easily).

 

3. Wash hands before sample collection and between dogs if more than one DNA sample is being collected. We are more interested in the dog’s DNA than yours.

 

4. Peel open the brush package about 1 inch at the arrow (the opposite end from the bristles). Remove the brush, being careful not to touch the bristles.

 

5. Place the brush between the lip and gum of the dog being tested, and gently brush the inside of the cheek using all sides of the round brush.

 

6. Place the brush back in the original labeled package, bristles in first.

 

7. Repeat steps 3-6 with the additional brushes for each dog. Please collect 2 brushes from each dog.

 

8. For shipment, tape the ends of each brush package closed, and bundle the brushes for each animal. Brushes for more than one dog can all be returned in the same package. The samples are stable without refrigeration and do not need overnight express mailing. Include in the package:

a. clearly labeled brushes

b. full payment

c. an address label with your address for us to use to return the results to you

d. pedigrees of the dogs submitted (optional, but appreciated)

9. The package should be sent by Priority Mail to:

Dr. John C. Fyfe

After May 20, 2002 our address will be:

Laboratory of Comparative Medical Genetics

2209 Biomedical Physical Sciences Bldg

Michigan State University

East Lansing, MI 48824-4320

Cost of the test: (NOTE cost will have increased and Dr. Fyfe is no longer with MSU) The cost of the test is $40.00 per dog. We regret that we are not able to offer a discount to those sending more than one sample. Please include an additional $5.00 for the brush kit. Please enclose a check for the total made out to: Michigan State University (CHG Test), and include it with the brushes.

 

How will I be informed of the result?: The result(s) will be mailed to you using the return address that you supplied. You will receive a Certificate with the name of the dog and the result. We regret that we cannot give out results over the telephone, but we will email if an Eaddress is provided. All results are strictly confidential and the results will only be released to the person who sent in the samples."

Editor's note: We ask all breeders to contact editor to report a confirmed occurrence of GHG in any breed for our privacy protected veterinary database. We also stipulate that we do NOT agree with Dr. Fyfe's oft-quoted assessment that "over 30% of Toy Fox Terriers are affected with CHG..."

Our researchers were however able to i.d. this statement which may account for that erroneous belief.... "and 56 (31%) of 181 TFTs tested to date have been identified as carriers. However, this percentage does not reflect a true carrier prevalence or gene frequency because a large bias in sample submission likely has occurred. In the population sample tested to date, a popular sire effect has been found on the distribution of CHG carriers that is recognized by many breeders and has created a significant motivation for testing." source credit https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1939-1676.2003.tb01323.x (offsite link, copy and paste URL in browser)

As is so correctly stated, a breeder or owner would be unlikely to have a dog tested for a condition which is fatal and readily discernable if present. If however, a dog had an affected or carrier relative, it would be prudent to test to determine if it too is a carrier.

For more information on other breeds (and species) affected by Congenital Hypothyroidism with Goiter, see Part 1 - CHG Introduction.

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