Motion concerning NTUAS

Background

Norwich Terrier Upper Airway Syndrome (NTUAS) is a term used to describe respiratory problems of the upper airway in Norwich terriers. NTUAS is considered the number one health problem of Norwich terriers.

A grading scheme of the canine upper airway was proposed in 2009 in a University of Berne (Switzerland) Ph.D. dissertation ([1]). This grading scheme requires that a dog be anesthetized and an endoscope inserted into the upper airway which allows a veterinarian to look at the upper airway. This procedure is informally called "scoping". Unfortunately this Swiss grading scheme was never published, has only been used by European Norwich breeders, and for various reasons was never adopted by Norwich breeders in the United States.

In 2019 a scientific paper ([2]) was published that reported on a DNA marker in the ADAMTS3 gene associated with NTUAS. Norwich with 2 copies of this "risk" marker are likely to have worse NTUAS airway scores (using the Swiss grading scheme) than dogs with no copy of the risk marker. 401 Norwich terriers were involved in this study. In 2020 VetGen, a DNA testing company, began marketing this ADAMTS3 DNA test for use by Norwich breeders.

A 2015-2019 research study at Michigan State University under Dr. Bryden Stanley - with help from researchers at UC-Davis, Texas A&M, and Penn - extended the Swiss work on NTUAS. This large (148 dogs) study of NTUAS was funded by the Norwich Terrier Club of America (NTCA) and cost approximately $100K. One of the objectives of the study was an airway grading scheme for use by Norwich breeders. The results of this study are currently being written up for publication.

In the fall of 2020, the airway grading scheme developed by Dr. Stanley was released and put on the website of the NTCA ([3]). In November 2020 Dr. Stanley gave a video talk describing her research on NTUAS ([4]).

In December 2020 the following motion was made to the board of directors of the NTCA:

MOTION - The NTCA recommends that breeding stock be tested for Norwich Terrier Upper Airway Syndrome.

The motion was referred to the NTCA health committee for comment. The NTCA health committee came back with a recommendation that the motion not be approved, and in February 2021 the board of the NTCA voted not to approve the motion.

Arguments in favor of the motion

Norwich Terrier Upper Airway Syndrome (NTUAS) is the number one health problem of Norwich Terriers. Norwich have collapsed and died from a poor airway, and many have required expensive surgery to improve their airway. NTUAS has been described as if the dog is breathing through a straw for its entire life.

The NTCA has spend approximately $100K on a major study of NTUAS, in part to develop a grading scheme of the upper airway that breeders can use as a tool to breed away from the problem.

Dr. Stanley, the head of the research study, in her VetVine talk in November at minute 59:30 in response to the question "Do you recommend that breeders scope and score their dogs and take the information into consideration when making breeding decisions?" responded "I think the score should be used in making breeding decisions, yes."

The motion says "tested for NTUAS". Currently there are two tests for NTUAS - the risk-marker ADAMTS3 DNA test (inexpensive, but less accurate), and UAS scoping (more expensive, but also more accurate). Scoping costs approximately $500 or more, whereas the ADAMTS3 DNA test costs $65. While the DNA test is easy to do at home (swab the inside of a dog's cheek), it is less accurate. But the DNA test does give some information about the dog's airway. For the dogs in Dr. Stanley's study with two risk-markers, approximately 60 percent had poor airways. Dr. Stanley in her VetVine talk recommended that it is better to breed from dogs with a low scoping score and that do not have two ADAMTS3 risk-markers.

The motion is worded so that a breeder can choose just one test, and still say that they are meeting the club's health recommendations for breeding. And when science comes up with a new NTUAS test, nothing needs to be changed - the NTCA will automatically be recommending it.

The motion only makes a recommendation; no breeder is required to test their dogs for NTUAS.

The motion says nothing about what dogs to breed. Breeders are free to breed a dog whether or not it has a good test score or not.

Arguments made against the motion (and rebuttal arguments).

1. Scoping is an invasive and risky procedure Scoping has always been known as an invasive procedure because of the anesthesia risk. However as invasive procedures go, the risk is low - some light anesthesia and an endoscope to look at the airway. A dental cleaning is more invasive and risky; a c-section is certainly more invasive and risky.

If the NTCA was not going to recommend an invasive procedure to its members, they why did the NTCA ask Dr. Stanley and the other researchers to spend their valuable time developing the scoping scoring criteria?

Breeders need to weigh the risk of anesthesia against the risk of breeding dogs who have trouble breathing their entire lives. NTUAS has been characterized as if the dog is breathing through a straw its entire life. Besides being uncomfortable that also can be life-threatening. For those breeders who think the risk of anesthesia outweighs the information that can be gained from scoping, then those breeders can do the ADAMTS3 DNA test - a less accurate but also less invasive test (only a cheek swab is required).

Question - What is the evidence that a dental cleaning is less invasive than scoping? The anesthesia during a NTUAS scoping has to be light enough so that a cough can be induced to check the saccules. Clearly a coughing dog would not be a good thing during a dental cleaning when the vet is working beneath the gum line with probes and other sharp instruments. So the anesthesia must be stronger - and hence riskier - during a dental cleaning.

There is another piece of evidence that the anesthesia risk is greater during a dental cleaning. Many Norwich breeders have had their dogs' airways scoped and a sacculectomy performed (a common operation to improve the airway) for years before Dr. Stanley started her study. (Some Norwich breeders may remember when Dr. Shultz in Michigan was the "goto" vet for scoping.) In all this time, there has not been any report of a Norwich dying from a UAS scoping procedure. However there have been reports of Norwich dying during a dental cleaning. Thus the obvious conclusion is that the anesthesia risk is greater during a dental cleaning.

2. Accessibility to expert veterinarians is a barrier Experts who can come up with the scoring criteria are rare and the NTCA was lucky to find Dr. Stanley and her co-PIs for the study. However veterinarians who can scope an airway and perform saccule surgery - the most common airway surgery - are much more available. Remember that the brachycephalic breeds also require scoping and frequently saccule surgery. Any specialty veterinary hospital has such vets. And some non-specialists also do these procedures. Norwich breeders are not alone in asking for these procedures from veterinarians.

It has been reported that one non-specialist vet doing Norwich airway scopings has remarked that the scoring criteria developed by Dr. Stanley is very descriptive and easy to use to score. Dr. Stanley went through several iterations when developing the scoring criteria in order to make the language as descriptive and clear to all.

3. The ADAMTS3 DNA test is inaccurate Two studies have now looked at the ADAMTS3 DNA test - Dr. Stanley and the Marchant paper that originally described the test. Both show the same thing - dogs with two copies of the ADAMTS3 risk marker have a greater likelihood of having poor airways. (See figure 6A in the Marchant paper and the slide at minute 53:00 of Dr. Stanley's Nov 2020 talk.) Dr. Stanley concluded that "Dogs homozygous for ADAMTS3 have increased chance of a higher NTUAS Score" (minute 54:38) (homozygous means having two risk markers; a higher score means a worse airway). Dr. Stanley also concluded "Better to breed from [a dog with a] low NTUAS Score and not HOM for ADAMTS3" (minute 55:10).

The ADAMTS3 DNA test is not a medical-grade diagnostic test, but rather a breeding tool. There are times when scoping is not an option. For example when a breeder is trying to decide which puppy or puppies from a breeding to keep. (As always, the total puppy must be taken into account, but perhaps one should pass on a puppy with two NTUAS risk markers.) Another example is when trying to decide between two stud dogs who have not been scoped. The ADAMTS3 DNA test gives the breeder information - not perfect information - but better information than flipping a coin.

4. Breeders will use the tests to include or exclude dogs from a breeding program. A recommendation to test does not mean that breeders will include or exclude dogs. One should never include or exclude a dog from a breeding program based upon a single item. Rather health testing gives breeders more information so that they can make better decisions. Different breeders will make different decisions based upon the same information - that is the art of dog breeding.

5. The club opens itself to legal liability. The NTCA has an expert witness (Dr. Stanley) on record (Nov 2020 video) recommending scoping. So the NTCA would have a strong defense if the club was sued. Also dogs are legally considered property in most states. Thus if the NTCA was sued and lost, the NTCA would only be liable for the price of the dog. So it is unlikely that the NTCA will be sued because of a testing recommendation, and if the NTCA is sued then the financial liability is low.

The question of legal liability also works in the other direction. After all, the NTCA knows that NTUAS is the number one health problem of Norwich Terriers, and knows that there are two tools breeders can use to breed away from the problem. By not recommending NTUAS testing, the club could be sued for the cost of upper airway surgery by angry owners.

6. Will testing adversely affect genetic diversity? Testing does not affect genetic diversity. It is the decisions breeders make with test results that affects genetic diversity. Breeders should never base breeding decisions on a single thing, but rather should take the whole dog into consideration. Genetic diversity is most affected by popular sires. So if genetic diversity is a concern, then one should advocate removing ribbons from conformation shows.

7. Those wishing to health test are in no way hindered by the absence of a club recommendation. It is also equally true that those choosing not to test are in no way hindered by a club recommendation to test.

Breeders criticize puppy mills for not health testing (and other things). What kind of a club is the NTCA if it does not recommend testing for its number one breed health problem?

8. NTUAS testing is a complicated issue not easily understood by the average breeder. This argument insults the intelligence of responsible breeders who are interested in producing healthy dogs. But assume for the moment that the argument is valid. In complicated situations people rely on "experts". Dr. Stanley is certainly an expert on NTUAS testing. Dr. Stanley recommends NTUAS scoping for breeding stock. What experts do not recommend testing for the number one health problem of Norwich terriers?

Blair Kelly
20210228, updated 20210309

[1] Das Obere Luftweg-Syndrom beim Norwich-Terrier: Beschreibung der Erkrankung und der Untersuchungsmethoden, sowie Entwicklung und Evaluierung eines zuchthygienisch nutzbaren Scoring-Schemas., Martina Ruchti, 2009.

[2] An ADAMTS3 missense variant is associated with Norwich Terrier upper airway syndrome, Marchant et al., PLOS Genetics, 2019.

[3] NTCA website, Norwich Health, NTUAS Score Sheet

[4] VetVine.com, Continuing Education, CE/Videos on Demand, "Upper Airway Syndrome - Results of a Cross-Sectional Study in Norwich Terriers" by Bryden J. Stanley, BVMS, MSc, MANZCVS, MRCVS, DACVS.