Copper Toxicosis (COMMD1) in Bedlington Terriers: What the DNA Test Can and Can’t Tell You

The short answer: COMMD1 is the gene where Bedlington Terrier copper toxicosis was first mapped, and it’s still an autosomal recessive fault: two copies cause disease, one copy makes a healthy carrier. A DNA test reports genetic risk, not a diagnosis — and because some Bedlingtons develop copper toxicosis through other genes entirely, a “COMMD1-clear” result does not fully rule the disease out in this breed.

If you own, breed, or are about to buy a Bedlington Terrier, “copper toxicosis” is probably a phrase you’ve already met on a breeder’s health certificate or a rescue’s adoption form. It is the breed’s defining inherited liver disease, and it is also one of the earliest successes in canine molecular genetics — the gene involved, COMMD1 (originally called MURR1), was mapped in this exact breed by a Dutch research group in the early 2000s. This article explains what the gene does, what a DNA test can and can’t tell you, and — because roughly a fifth of the world’s Bedlington Terriers are registered in the UK, where the breed originates — how to actually get tested, referred, and insured here, with a US section alongside it.

The molecular mechanism: what COMMD1 does in a healthy liver

Copper is an essential trace nutrient, but only within a very narrow range. Hepatocytes (liver cells) take in dietary copper, use what they need for enzyme function, and export the surplus into bile via a transporter protein called ATP7B — the same transporter implicated in human Wilson disease. COMMD1 is not the exporter itself; it is a regulatory protein that interacts with ATP7B and the broader intracellular copper-trafficking machinery inside hepatocytes, helping direct excess copper toward biliary excretion rather than toxic accumulation.

When COMMD1 is lost, ATP7B-mediated copper export becomes inefficient even though the ATP7B gene itself is structurally normal. Copper that should have left the liver in bile instead accumulates, slowly, inside hepatocytes over months and years. This is mechanistically analogous to human Wilson disease in its endpoint — progressive hepatic copper overload — but it is genetically distinct: Wilson disease in people is caused by mutations in ATP7B itself, whereas classic Bedlington Terrier copper toxicosis is caused by loss of a regulatory partner protein, not the exporter.

What the DNA test actually tells you

The genetic cause of copper toxicosis in Bedlington Terriers was identified by positional cloning in a study led by van De Sluis, Rothuizen, Pearson, van Oost and Wijmenga, published in Human Molecular Genetics in 2002 — a landmark paper because it used a purebred dog population’s unusually long runs of shared DNA to find a gene relevant to human copper metabolism (van De Sluis et al., 2002). Three years later, Forman and colleagues characterised the exact structural change: a 39.7 kb deletion spanning exon 2 of COMMD1, located on dog chromosome 10 (Forman et al., 2005).

The inheritance pattern is autosomal recessive. That means a dog needs one copy of the deletion from each parent to be affected. A dog with one copy is a clear-but-unaffected carrier; a dog with zero copies of the deletion is genetically clear at this specific locus. A commercial COMMD1 DNA test reads exactly this: how many copies of the 39.7 kb deletion a dog carries. It is a genotype report, not a liver function test, and it cannot tell you a dog’s current copper level or whether disease has already started.

SamMy Bedlington came back COMMD1 clear — so copper toxicosis is off the table for good, right?

Elena MarshNot quite. Forman’s team pinned the exact 39.7kb deletion in 2005, and that test is very reliable for that specific fault. But it only tests that one fault.

Clinical picture: from silent carrier to liver cirrhosis

Left unmanaged, copper toxicosis is progressive and, in its later stages, life-threatening. According to the Orthopedic Foundation for Animals, clinical signs include lethargy, depression, anorexia, vomiting, weight loss, diarrhoea, excessive thirst, abdominal distension, jaundice, and dark urine (OFA, Copper Toxicosis). These signs typically reflect a liver that has already been silently accumulating copper for a long time — early- and mid-stage copper accumulation is often clinically invisible, which is precisely why genetic screening and periodic liver monitoring matter more than waiting for obvious symptoms.

Untreated, the disease progresses to hepatitis and then progressive cirrhosis of the liver. This progression is not instantaneous or guaranteed to follow the same timeline in every dog, and dietary copper restriction and copper-chelating veterinary treatment can meaningfully slow or manage the process in affected dogs — but neither a DNA test nor any current treatment constitutes a cure, and any dog showing the symptoms above needs a vet, not a wait-and-see approach.

Important: why a “COMMD1-clear” result isn’t a clean bill of health

This is the single most important nuance for Bedlington Terrier owners to understand, and it is a relatively recent finding. A 2023 study by Haywood and colleagues, published in Veterinary Record, found that some Bedlington Terriers without the COMMD1 deletion still go on to develop copper toxicosis, associated instead with splice variants in ABCA12 or with variants in ATP7B itself (Haywood et al., 2023). In other words, copper toxicosis in this breed is not caused by a single gene fault; it can arise through at least three independent genetic routes, only one of which — COMMD1 — is covered by the classic, widely available commercial DNA test.

The practical consequence: a COMMD1-clear Bedlington Terrier has ruled out the original, best-characterised cause of the disease, but has not ruled out copper toxicosis altogether. Owners of COMMD1-clear dogs who see any of the clinical signs above should still take them seriously and discuss liver enzyme monitoring with a vet, rather than assuming the DNA result closes the question permanently.

Clear, carrier, affected: genotypes and breeding management

Standard COMMD1 test reports use three categories:

• Clear (N/N): zero copies of the 39.7 kb deletion. Will not develop COMMD1-related copper toxicosis, but see the caveat above.
• Carrier (N/CT): one copy of the deletion. Not expected to develop disease from this locus alone, but passes the deletion on to roughly half of its offspring.
• Affected (CT/CT): two copies of the deletion. At very high risk of developing copper toxicosis during its lifetime.

For breeding, the standard, genetically sound approach is never to mate two carriers or a carrier with an affected dog, since that risks producing affected puppies. A carrier can safely be mated to a clear-tested dog: none of the resulting puppies will be affected, though roughly half will themselves be carriers and should be tested before they are, in turn, considered for breeding. This lets breeders retain genetic diversity in a numerically small breed rather than removing every carrier from the gene pool outright.

Getting the test done in the UK

Because Bedlington Terriers originate in Northumberland and the breed’s main population and specialist expertise remain concentrated in the UK, this is genuinely a “get it done locally” test rather than something that needs sending abroad. Several UK laboratories offer a COMMD1 test built on the Forman et al. deletion assay, including Laboklin (UK), whose Copper Toxicosis COMMD1 test costs £48.00 including VAT with a stated turnaround of around 2–3 weeks, and Canine Genetic Testing (CAGT), whose equivalent test is priced at £49.50 including VAT with a faster stated turnaround of around 1–2 weeks. Both labs accept a non-invasive buccal (cheek) swab, and Laboklin also accepts an EDTA blood sample if a vet is drawing blood for another reason anyway. Typical process: order the kit online (or get a free swab kit posted to you), swab the inside of both cheeks per the enclosed instructions, and post the sealed sample back with the completed submission form — no sedation, no clinic visit strictly required for a swab-only submission, though many owners have their vet take the sample at a routine appointment.

For US-based readers, the equivalent domestic option is the UC Davis Veterinary Genetics Laboratory Copper Toxicosis panel, which — reflecting the Haywood 2023 findings — actually tests for the ATP7A/ATP7B variants rather than the COMMD1 deletion; American owners who specifically want the classic COMMD1 39.7 kb deletion result should check the exact assay offered before ordering, since “copper toxicosis test” is used loosely across different labs for different underlying variants.

Sam£48 for a cheek swab feels almost too cheap for something this serious.

Elena MarshIt’s cheap because it’s a single known deletion, not a whole-genome scan. Laboklin UK runs it for £48 including VAT, turnaround about two to three weeks.

The UK vet referral pathway: from GP practice to hepatology specialist

A DNA test result is not, by itself, a reason to panic — but it is a reason to plan. For a genetically at-risk (carrier or affected) Bedlington Terrier, the sensible next step in the UK is a conversation with your primary-care vet about a baseline liver panel, typically including ALT and other liver enzymes, plus bile acids if indicated, so you have a reference point before any symptoms appear. Many general practices are comfortable managing routine monitoring and diet discussions themselves; where results are abnormal or the picture is unclear, primary vets in the UK can refer on to a specialist in veterinary internal medicine or hepatology, usually at a referral hospital, for more detailed liver function testing, imaging, or liver biopsy if a definitive copper quantification is needed. Bring any DNA test paperwork to every appointment — it materially changes how a vet interprets borderline blood results in this breed.

Pet insurance and copper toxicosis: what UK and US policies actually say

Insurance treatment of a known hereditary risk varies by insurer and by whether your dog already has symptoms when you take out the policy. In the UK, Petplan states that it reviews pre-existing conditions on a case-by-case basis, and specifically that “if the condition is likely to affect the dog for the rest of its life… we’d unfortunately not be able to cover costs attached to that particular ailment at any point in the policy” once it has shown symptoms — which is the key reason to insure a Bedlington Terrier puppy before any liver abnormality is ever recorded, rather than after. A positive carrier or affected DNA result recorded before symptoms appear is generally not itself treated as a pre-existing condition by UK insurers in the way an actual diagnosed illness would be, but always confirm this in writing with your chosen insurer before relying on it.

In the US, both Trupanion and Healthy Paws advertise coverage for hereditary and congenital conditions as standard, provided no signs or symptoms were present before the policy’s effective date (and after any waiting period). As with the UK, the practical takeaway is the same: insure early, ideally as a puppy, well before any liver enzyme abnormality or symptom is ever recorded in a vet note, and read the specific policy wording for your chosen provider rather than assuming coverage.

SamSo the trick is just insuring the puppy before any of this shows up on a vet record?

Elena MarshExactly the logic UK insurers use — Petplan’s own wording says a lifelong condition can’t be covered once it’s shown symptoms, so timing the policy matters more than the DNA result itself.

Kennel Club health scheme, AKC registrations, and the absence of a legal mandate

In the UK, the Kennel Club supports a voluntary COMMD1 health screening programme for Bedlington Terriers, alongside the breed’s participation in the BVA/KC/ISDS eye scheme, and lists DNA testing among its recommended (rather than legally compulsory) breed health practices; Assured Breeders receive a discount on Kennel Club DNA testing services as an incentive. There is no UK law requiring a breeder to genetically test breeding stock for COMMD1 or to disclose results to puppy buyers — the enforcement mechanism is entirely reputational and scheme-based, via the Kennel Club’s own registers and Assured Breeder standards, not statutory.

In the US, the pattern is similar: the Bedlington Terrier Club of America, working with the Orthopedic Foundation for Animals’ Canine Health Information Center (CHIC), recommends a copper storage disease DNA test as the breed’s key CHIC-relevant screening, and dogs completing recommended tests can be awarded a CHIC number — but again, this is a voluntary breed-club registry, not a legal requirement, and the AKC itself does not mandate DNA testing for registration. For context on scale, the Bedlington Terrier ranked No. 134 out of 201 breeds in the AKC’s 2024 US registration statistics (AKC, Most Popular Dog Breeds 2024), reflecting its status as a numerically small, specialist breed on both sides of the Atlantic — which is itself part of why responsible, voluntary genetic screening within the breeding community matters so much: there simply isn’t a large enough population to absorb careless breeding decisions without measurable impact on the gene pool.

What Bedlington Terrier owners can do today

• Get (or ask your breeder for) a COMMD1 DNA test result — in the UK this is a low-cost cheek swab from Laboklin UK or CAGT, typically £48–£50 with a one-to-three-week turnaround.
• Remember that a clear result rules out the classic COMMD1 deletion, not copper toxicosis in general — the 2023 Haywood findings on ABCA12/ATP7B mean watchfulness still matters even in clear-tested dogs.
• Ask your vet about a baseline liver enzyme panel (ALT and related markers) for any carrier, affected, or even clear Bedlington Terrier, and repeat periodically as your vet advises.
• Insure early — ideally as a puppy, before any liver-related symptom or abnormal result is ever recorded — and get your chosen insurer’s exact wording on hereditary and pre-existing conditions in writing.
• If breeding, never pair two carriers or a carrier with an affected dog; pair carriers only with DNA-confirmed clear dogs, and test resulting carrier puppies before they are considered for future breeding.

FAQ

Q. Is copper toxicosis unique to Bedlington Terriers?
The specific COMMD1 deletion described by van De Sluis (2002) and Forman (2005) was identified in and is strongly associated with Bedlington Terriers, which is why the breed is the classic model for this disease. Other breeds can develop different forms of copper-associated liver disease through different genetic mechanisms, but that is a separate topic from the Bedlington-specific COMMD1 deletion discussed here.

Q. My Bedlington Terrier tested as a carrier. Does that mean it will get sick?
No. A single copy of the COMMD1 deletion (carrier status) is not expected to cause copper toxicosis on its own under the classic autosomal recessive model. The concern with carriers is primarily for breeding decisions, not for the individual dog’s health — though routine liver monitoring is still a sensible precaution given the Haywood 2023 findings on non-COMMD1 causes.

Q. Can copper toxicosis be cured?
There is no cure, but with veterinary management — typically dietary copper restriction and, where indicated, copper-chelating medication — the disease’s progression toward hepatitis and cirrhosis can often be slowed and managed. This is a lifelong management condition, not a one-off treatment, and it needs to be overseen by a vet.

Q. Should I get a liver biopsy instead of a DNA test?
They answer different questions. The DNA test tells you genetic risk (does this dog carry the known deletion) non-invasively via a cheek swab; a liver biopsy is an invasive procedure that directly measures current liver copper concentration and tissue damage, and per OFA guidance is generally not performed before 12 months of age. Most owners start with the DNA test and use it to decide, with their vet, whether and when more invasive diagnostics are warranted.

Q. Is DNA testing legally required to breed or register a Bedlington Terrier in the UK or US?
No. In both countries, COMMD1 testing is a strongly recommended, voluntary practice supported by the Kennel Club’s health screening programme and the Bedlington Terrier Club of America/OFA CHIC registry respectively — not a statutory requirement enforced by any registration authority.

References

• van De Sluis B, Rothuizen J, Pearson PL, van Oost BA, Wijmenga C (2002). “Identification of a new copper metabolism gene by positional cloning in a purebred dog population.” Human Molecular Genetics 11(2):165-173. PubMed
• Forman OP et al. (2005). “Characterization of the COMMD1 (MURR1) mutation causing copper toxicosis in Bedlington terriers.” Animal Genetics. PubMed (PMID 16293123)
• Haywood S et al. (2023). “Copper toxicosis in Bedlington terriers is associated with multiple independent genetic variants.” Veterinary Record. Wiley / Veterinary Record · PubMed (PMID 37038639)
• OMIA:001988-9615, Online Mendelian Inheritance in Animals. omia.org/OMIA001988/9615
• Orthopedic Foundation for Animals. “Copper Toxicosis.” ofa.org/copper-toxicosis
• Laboklin (UK). “Copper Toxicosis COMMD1 / CT (Copper Storage Disease).” laboklin.co.uk
• Canine Genetic Testing (CAGT). “Copper Toxicosis.” cagt.co.uk
• UC Davis Veterinary Genetics Laboratory. “Copper Toxicosis (Menkes and Wilson diseases).” vgl.ucdavis.edu
• The Kennel Club. “DNA test – COMMD1 (Copper Toxicosis).” royalkennelclub.com
• Petplan UK. “Pet insurance for pre-existing conditions.” petplan.co.uk
• Trupanion. “Are hereditary and congenital conditions covered?” trupanion.com
• Healthy Paws Pet Insurance. “Hereditary and Congenital Conditions in Pets.” healthypawspetinsurance.com
• American Kennel Club. “Most Popular Dog Breeds of 2024.” akc.org

Photo: A Bedlington Terrier puppy, CC BY 2.0, via Wikimedia Commons.

About the author

Elena Marsh

Editor & writer (not a veterinarian)

A writer with a molecular-biology background and a lifelong dog and cat owner. Not a veterinarian — she translates peer-reviewed genetics research and primary data into plain language, always as information rather than diagnosis.