CT - The Disease

(Note - Copper toxicosis may alternatively be referred to as Copper Storage Disease, Copper Storage Hepatitis, Copper Hepatoxicosis, Hepatic Copper Toxicosis or Copper-associated Hepatopathy in scientific publications, particularly where these are of non-UK origin)


The BTHG wish to express their thanks to Roger Bannister (MRCVS) for his help in preparing these notes.


These notes should be read in conjunction with the accompanying notes from Dr Susan Haywood and with the Report on the CT Seminar



Introduction.


Copper is one of several essential elements that are necessary for survival but that need to be provided in the dogs diet only in very small amounts, i.e. as micro nutrients.  It is thought that copper is involved in a wide range of biological processes in the body and 3 important roles have been identified:





Under normal circumstances adequate copper is provided in the dog’s diet and there is no necessity to provide any form of supplement.  Only sufficient copper to satisfy the dog’s physiological needs is retained in the liver and copper surplus to these requirements is converted by a series of enzymes into a form that can be incorporated into bile, which is manufactured in the liver.  This bile is then stored in the gall bladder prior to being secreted into the small intestine and excreted in the faeces.


However, copper is highly toxic if levels within the body exceed the normal physiological need of the dog.  Hence, if this regulatory mechanism should fail, for whatever reason, copper will accumulate in the liver and this will result in copper toxicosis.


This regulatory activity is genetically determined.



The cause of Copper Toxicosis.


Copper toxicosis in Bedlington terriers is a progressive degenerative disease of the liver which results directly from the malfunction of the enzyme system responsible for processing the surplus copper in the liver cells.  Any malfunction of this enzyme system leads to an accumulation of copper in the liver tissues.  In other words, copper toxicosis results from the inability of the affected dog to mobilise and excrete dietary copper which is surplus to its requirements.


The copper content of liver tissue of a healthy dog varies within the range 20-70 µg per gm liver tissue `wet' weight which equates to 100-400 µg per gm liver tissue “dry” weight.  In dogs affected with copper toxicosis the level of copper in the liver tissue is considerably higher than this and is often 1000-2500 µg per gm liver tissue “dry” weight.  It may even exceed 10,000 µg.  The critical level for the diagnosis of the “affected” status is generally accepted to be 1000 µg per gm liver tissue dry weight.


Copper toxicosis in Bedlington terriers was first reported in 1975 in the USA by Hardy, Stevens and Stowe and has since then it has been recognised in a number of other countries.  It was established later (Johnson et al, 1980) that the form of the disease found in Bedlingtons terriers was apparently caused by the presence of an autosomal recessive gene in affected dogs - it is a genetic disorder and in order for the condition to develop in a dog/bitch a copy of this defective gene must have been passed to the affected animal by both parents, i.e. the affected dog must have two “copies” of the defective gene in its body cells.


The form of copper toxicosis which affects Bedlington terriers is often referred to as “copper storage disease” and is regarded as a “primary” copper disorder.  In this context, the term “primary” is used to denote that the condition is direct consequence of the accumulation of copper in the liver tissues and is a direct result of the presence of the inherited “copper accumulation” genes, i.e. it is not the consequence of a malfunction caused by another factor such as damage to the gall bladder which would impair the removal of bile and therefore copper.


In 1986, Thornburg and his co-workers reported that this primary form of copper toxicosis has also been recognised in West Highland Terriers.  Although there have been reports that copper toxicosis has been diagnosed in other breeds, there appears to be some confusion in the literature about whether or not these reported cases refer to secondary copper storage disorders, i.e. that the development of the copper toxicosis is a result of other factors which caused liver malfunction.



The Incidence of inherited Copper Toxicosis.


In 1979, it was suggested (Twedt et al.) that the incidence of copper toxicosis in Bedlington terriers in the USA may be as high as 50% and another source suggested that 66+% of Bedlingtons may be affected.  However, it was thought that the situation in the UK was somewhat better.  An investigation into the status of 92 Bedlingtons carried out by Herrtage and his fellow workers, reported in 1987, recorded an incidence of 33.9% even though none of the dogs in the survey showed clinical signs of liver disease.  


Please note that the figure of 33.9% “affected” dogs quoted above relates to a survey done on the results from dogs that had been liver biopsied and no indication was given about the number of dogs considered to be “normal”. Moreover, the figure relates to the situation as it was in the mid-1980s.  Considerable care is needed when interpreting any data obtained from a limited sample of dogs and extrapolating the information to project the national situation. However, it was obvious that there was a serious problem.


An incidence level of 36% was also reported in the Netherlands.



The Disease.


Copper toxicosis is a complex, genetic disorder.  In affected animals, i.e. those dogs that have inherited two copies of the mutation, the concentration of copper in the liver tissue starts to increase progressively from an early age and reaches significant levels by the time it is 6 months old.  Unfortunately, this does not necessarily result in the development of overt, clinically observable symptoms - Thornburg and his colleagues (1985) reported that overt clinical signs of liver disease do not generally occur until the dog is several years old.  Moreover, Hardy and Stevens (1978) stated that many affected Bedlington terriers may never develop any clearly recognisable signs even though they have high liver copper levels and irreparable damage will have been done to the liver.


It is generally accepted that there are three “forms” of the disease:


1.       Asymptomatic Copper Toxicosis.


These dogs show no overt indications of being affected even though examination of the liver tissue would show them to be “affected”.  Research indicates that a high proportion of affected dogs fall into this category and many live a seemingly normal life - the results of a survey carried out in the USA indicate that relatively few affected dogs die at a significantly earlier age than normal as a result of the copper toxicosis, i.e. the mortality rate is relatively low.


Significantly, however, the condition in some asymptomatic dogs may progress to present as overtly clinical disease.  There are two recognised forms of clinical copper toxicosis :


2.       Acute copper toxicosis.


In some cases an affected asymtomatic dog may suddenly become acutely ill as a result of acute liver failure.  This form of copper toxicosis is usually seen in young adults, i.e. 2-3 year old dogs, and is often precipitated by “stress”.  The dog will become jaundiced, (due to breakdown of red blood cells as well as liver damage), with diarrhoea and vomiting.  The prognosis is poor and despite intensive therapy the dog usually dies within 2-5 days

3.       Chronic overt copper toxicosis.


Chronic overt copper toxicosis commonly occurs in older dogs, typically at about 6-7 years of age and manifests itself as a slow progressive development of clinical signs. These vary considerably and are typical of liver diseases in general.  These signs include:-



These signs, which could be attributed to a number of causes, are very often poorly defined or not specific and are very often overlooked, particularly in the early stages of development/progression of the disease.



Identification of affected dogs.


Copper toxicosis was first recognised in the USA in the mid 1970’s.  Subsequent research established that it was a genetic disorder and the evidence suggested that it was caused by an autosomal recessive mutation inherited on classical Mendelian lines.


An unfortunate characteristic of the inherited form of copper toxicosis is that irreversible adverse changes occur in the liver tissue a considerable time before any overt signs of the disease occur in the dog.  Moreover, in many cases these signs do not develop or their significance is not recognised.


1.       Liver Biopsy.


Initially, the only way in which affected animals, i.e. those with copper toxicosis, could be identified was by examination of liver tissue samples.  This involved:


a.  Determination of the amount of copper, measured in micrograms per gram.

b.  Histo-chemistry to check the level of visible stainable copper

c.  Histo-pathology to check for  changes in the liver cells that are characteristic of copper toxicosis


Unfortunately, this technique will only differentiate between a “normal”, i.e. unaffected dog, and one that is “affected”.  It does not identify “carriers”, i.e. those dogs carrying only a single copy of the mutation.


This is a serious shortcoming because of the significance of dogs that would/could be classed as “carriers”and which would never develop copper toxicosis but, never-the-less, had the potential to pass on a copy of the mutant gene to their offspring.


Moreover, liver biopsy involves invasive surgery necessitating the use of an anaesthetic.


However, until such time as a genetic (DNA) test could be developed, the use of liver biopsy as a diagnostic test continued.


2.       Genetic  (DNA) Tests.


Obviously, a genetic test would be more effective in that it would allow differentiation between the normal, carrier or affected status.


The DNA required for the test can be extracted from a cheek cell swab, eliminating the need for invasive surgery.  Obtaining a cheek swab is a straight-forward procedure and is usually carried out by the owner of the dog.   A major advantage of genetic  tests is that samples for testing can be submitted from puppies - the results are generally available within 5-6 weeks, i.e. long before any puppy which is shown to be affected will begin to accumulate significant amounts of copper in the liver.


Note: Although a blood sample may occasionally be used for DNA extraction, the sample can only to be taken by a veterinary surgeon.


The first DNA test to be made available was the CO4107 marker test, developed by Vetgen in the USA and adopted by the Animal Health Trust in July 1996 following a trial to assess its suitability for use in the UK. This was an indirect test based on the identification of a small section of DNA which had been found to be associated with the mutation thought to cause copper toxicosis.  Unfortunately, it soon became apparent that anomalous results were occurring.  This was attributed to “recombination” taking place between the marker and the actual gene during the formation of gametes (sperm and eggs), resulting in the marker normally associated with the mutant gene and that associated with the normal gene being “switched over”.


Research into the genetics of copper toxicosis continued and in 2002 A.J.A.van de Sluis and his co-workers at the University of Utrecht announced that they had identified what was, seemingly, the causative gene - the COMMD1 gene (originally named the MURR1 gene). The team identified the mutation as a large deletion in exon2 of the COMMD1 gene and further established that the marker, previously used as the basis for the initial DNA test, was an integral part of this gene.  This discovery virtually eliminated the premise that recombination was the cause of the anomalous results obtained with the CO4107 marker test.


A new DNA test (the COMMD1 test) was developed and was introduced by the AHT in July 2005.  However, evidence has accumulated over time that supported the speculation that a second gene may be involved. Research is currently being undertaken to attempt to resolve this issue and although considerable progress has been made there is still much work to be done - for the latest information click Here.


An explanation of how the test results from the CO4107 marker test and the COMMD1 test are interpreted can be found at:


aht.org.uk


Scroll down to the bottom of the Home page and click on “DNA testing” in the “What We Do” list.  Click on “Canine DNA Testing” in the “Related Links” panel and then scroll down the page to make the appropriate links for “Bedlington terrier” - “Copper Toxicosis”.  


Vetgen.com


At the bottom of the home page click on “Learn More Canine …” under ”DNA Disease and Genetic Testing” and then click on “CT” in the “Genetic  tests “ list.


Note:


Although the COMMD1 test, seemingly, had the potential to identify the CT status of a dog, it became evident that some results were incorrect.  Consequently, despite the fact that it cannot identify the “carrier” status, examination of tissues obtained by means of a liver biopsy still remains the method for positively diagnosing the disease, i.e. of identifying affected dogs.  Moreover, it remains the only way whereby any new DNA test can be validated.  



Treatment of affected dogs.


Note:


The signs/symptoms of overt copper toxicosis are those which could be attributed to a number of conditions, e.g.

other forms of hepatitis, Cushing’s Syndrome, etc that can affect Bedlington terriers.  It is essential that a positive diagnosis is made as soon as possible in order that the appropriate medication, e.g. copper-chelating agents etc can be given.


Unfortunately, there is no treatment to reverse the situation once the copper induced liver damage has occurred. However, if the dog/bitch is identified as an affected animal at an early age, it is possible to take steps to prevent/minimise the possibility of it developing clinical disease.  Obviously, the sooner the status of the dog is determined the greater the chance of a successful response to treatment.




      However, many dogs seem to be reluctant to eat this type of diet in which case some form of “home-made       diet should be tried.

  

Suitable ingredients include:


Chicken/cooked rice/pasta/milk products (unflavoured cottage cheese or natural yoghurt).

Eggs (hard boiled or scrambled).

Potato (boiled but unsalted)

Vegetable oil (olive or sunflower oil).

White fish.


Avoid:


Offal (liver/kidney/heart/viscera).

Red meat.

Oily fish/shellfish.


The veterinary surgeon should be able to advise on suitable ingredients and the formulation of a diet, including the type of mineral/vitamin supplements.


Whichever type of diet is used it should be fed on a “little and often” basis and it may be necessary to “hand-feed” the dog, certainly in the first instance, in order to encourage the dog to eat.  It is also advisable to run off “standing water” from the tap before drawing fresh drinking water for the dog.  It is important to monitor food intake and body weight.


A low copper diet, if fed at an early stage  may prevent development of the disease.



Note:


The use of Distamine can result in side effects which can be severe some dogs.  However, they usually shows as nausea and vomiting. Your veterinary surgeon should  be consulted if this occurs.




The treatment of a dog diagnosed with chronic copper toxicosis is based on the preventative measures mentioned above but, in addition, the veterinary surgeon may prescribe antibiotics, steroids and other drugs.



Note: Acute hepatitis, irrespective of its cause, requires immediate hospitalisation by your veterinary surgeon for intensive care.




Understanding Bedlington Terrier Copper Toxicosis

 (Dr Susan Haywood)



Copper toxicosis results from a failure of the body to regulate its copper content.  In plain terms it is a failure to get rid of the excess copper taken into the system from the diet.



What is excess copper?


Copper is necessary for survival and is taken in with food in generally more than sufficient quantities.  However, it can be highly toxic over a certain level and normally only sufficient for the support of life is stored in the liver and any extra to requirement is packaged and excreted into the bile.  If this normal regulatory process is not working properly then copper will accumulate and can damage the liver.  This regulatory activity is genetically determined and if mutations occur in the gene or genes responsible it results in the build up of copper and a toxicosis which can occur in people with Wilson’s disease and in some breeds of dogs, principally Bedlington terriers.  Copper toxicosis also occurs in sheep particularly some breeds (North Ronaldsay) which makes it similar in this respect to the canine disease.



What is normal copper? 


In a survey involving 154 Bedlingtons we found a mean value in unaffected Bedlingtons (1year and over) to be 181µg/g DW with a range of 20-385 µg/g (Haywood et al, 2001).  This tallies well with reports from others and generally it is acknowledged that over 400 µg/g is abnormal. This is the level of copper that I refer to as the upper safety threshold.  It is a biological threshold - there is no sliding scale of complete safety above this level.  In depth biochemical investigations coupled with electron microscopy have shown that at this threshold the balance between safety and toxicity of copper becomes very unstable and liver damage, involving a process known as oxidant stress, becomes very likely.



Does copper in excess of the threshold level of 400 µg/g always cause clinical disease?


No, not always.  Sensitive indicators of liver damage such as blood liver enzymes ALT, AST, GDLH are invariably elevated and low level pathological changes can be seen under the microscope but this is not necessarily experienced by the animal as disease i.e. ill health.  Very often the dog will continue to accumulate copper which it manages to tolerate by a combination of efficient ‘packaging’ of the dangerous metal (a process known as sequestration) and natural antioxidant chemicals which it produces in response to the oxidant stress.  This process can continue for months and years until the liver is sufficiently damaged (cirrhosis) to result in liver failure and the result is classical copper toxicosis with liver copper well into the thousands (1000-14,000 µg/g).



Copper toxicosis can take different forms.


Animals vary in their ability to protect themselves against the damaging effects of copper and this natural variation is possibly responsible for the different forms the disease can take.

Thus, in 30 yrs of studying well over 200 Bedlington livers I have observed a wide spectrum of liver damage and disease.  Illness can occur at concentrations of just a little over the threshold level of 400 µg/g and anywhere in between up to a liver copper concentration of 14,000 µg/g with irreversible liver damage (cirrhosis).  I have also observed dogs which had died from ‘old age or natural causes ’ that on autopsy had levels of liver copper up to 10,000 µg/g, a copper toxicosis which had been undetectable to their owners.  Again I have encountered dogs which have undergone a fatal haemolytic crisis at comparatively modest levels of copper excess and paradoxically animals in which the build up achieved a plateau and even fell with time.  These marked variations in the manifestation of liver disease (or phenotype) may be genetically determined or may be a result of environmental effects such as stress.  We just don’t know.



What are the genes that can control copper storage within the liver?


With the advent of micro-satellite markers in late 1990’s Bedlington CT came to be associated with the presence of what is known as the 2-2 C04107 allele on a particular chromosome. Dogs carrying the 1-1 allele were considered free whilst 1-2 dogs were carriers.  In 2002, the apparent causative gene MURR1 (COMMD1)was identified by Dutch van den Sluis and co-workers which later was shown to contain the C04107 marker within the gene.


Around this time we at Liverpool began to diagnose CT in Bedlingtons with 1-1, and 1-2 alleles some of which had died and lead to our publishing our findings in the Journal of Small Animal Practice (2001) 42,181-185.  This was later confirmed genetically by both US and Australian workers who found such CT affected dogs lacking the exon deletion in COMMD1 gene.



Search for the 2nd copper toxicosis gene.


The hunt is now on for other copper toxicosis gene(s).  We have a grant from the UK Kennel club to look for the gene(s) and Dr Diane Cox of Canada is similarly engaged in a complementary study.


We, at Liverpool, have amassed a data bank of Bedlingtons affected by copper toxicosis but lacking the COMMD1 gene deletion and possessing microsatellite DNA markers 1-1 or 1-2.  It is too early to say whether there is a difference in phenotype between the classical 2-2 form of the disease but this aspect is under scrutiny.


However it is accepted that COMMD1 is not the only copper storage gene in Bedlington terriers.  Indeed, according to Professor Cox, not even the main gene!  In saying this it would not be unusual since many if not most canine disease is associated with more than one and in some cases many genes.




Update on Copper Toxicosis Research.


The research project to identify the postulated “second CT gene” has now been completed.  The results of the research were presented at an International Conference in Naples towards the end of 2014 and were well received by the conference delegates.  A “peer reviewed” paper has now been published in the February 2016 issue of the “Journal of Trace Elements in Medicine and Biology”.  


Click Here to view a copy of the research paper


One could say that this is now the end of Stage 1.  The next step will be to obtain funding to develop a new DNA test for this second gene and then to establish a new testing protocol .  It is highly probable that the new test will be used “in parallel” with the existing COMMD1 test, i.e. the 2 tests will be carried out separately using the DNA extracted from a single cheek swab submitted by the dog’s owner.


An important sequel to the introduction of the new testing regime will be the need for validation.  This is particularly pertinent in view of the fact that analysis of the research data has suggested that in some cases there may be other factors involved in the development of the condition.




The BTHG Report, 2017, including the latest report on Copper Toxicosis research.


DNA Genome Sequencing.


Recent good news was the announcement by Catherine Mellersh, at the Breed Health Coordinators Symposium, that The Animal Health Trust have now completed the DNA Profile Sequencing for Bedlington Terriers.  This may help in the proposed research soon to be carried out by a group which Dr. Susan Haywood has brought together, including Prof. Mike Herrtage, which will be mainly centred in Cambridge.


This research is to develop what they have found, i.e. the ABCA12 gene, a gene important in dogs which develop CT.  In order to complete one part of the programme Dr. Haywood requires a few dogs with 2 deletions in COMMD1 (2:2’s), preferably dogs which have also been biopsied.  This is to confirm whether or not ABCA12 is involved in CT in these dogs. (See Dr Haywood’s update below).



Copper Toxicosis in Bedlington Terriers – an update


Since copper toxicosis (CT) was recognised in Bedlington terriers in the UK and in other countries studies have been carried out to identify the mutant gene or genes responsible. Early studies identified an association with a deletion in the COMMD1 (Chr10) gene and genetic testing for this mutation has been used for screening for breeding. However significant numbers of biopsied affected Bedlington terriers which have only one or no COMMD1 deletions have been reported in the US, UK and Australia. Copper storage diseases (CT) have also been reported in other breeds notably Dalmatians, Labrador retrievers, Dobermann Pinchers and West Highland White Terriers. In none of these other breeds has the COMMD1 mutation been demonstrated to in any way identify affected dogs.  Dogs which are both 1:1 and having no deletions, which never-the-less biopsied affected, proved that in some dogs at least COMMD1 was not causing them to have CT since their COMMD1s are completely normal and therefore functioning normally. Hence it was demonstrated that another gene must be involved in producing CT in these dogs.


A study in the UK was undertaken on biopsied affected Bedlington terriers which have one or both COMMD1 genes which do not have the mutation currently DNA tested for.  This study identified a highly significant link to identifying CT status on Chr 37 containing variant SNPs on the ABCA12 gene9. This gene encodes for ABCA12, a metal binding protein bearing a close functional relationship to ATP7B responsible for Wilsons disease in humans. Put more simply the gene ABCA12 has a known role in Copper metabolism which is very similar to the role of the gene which has been found to cause Wilson’s Disease (CT) in humans.  COMMD1 on the other hand does not have any direct role in Copper metabolism. Concurrently a study in Labrador retrievers has identified a mutant variant of ATP7B (Chr22) the Wilson disease copper transporter gene in their affected dogs while COMMD1 does not appear to be involved in affected dogs in this and other breeds.


In an effort to clarify what appears to be a confusing situation Liverpool (Dr Susan Haywood, Prof Stuart Carter), and Cambridge (Dr Penny Watson, Prof. Mike Herrtage) veterinary schools have joined forces to try to obtain funding from the Kennel Club to study submitted tissue (blood, liver) from Bedlington terriers affected with copper toxicosis with respect to their DNA profiles COMMD1, ABCA12 and ATP7B. We hope to include other affected dogs from target breeds in the survey.


In the meantime, we have become aware that more non-COMMD1 (i.e. dogs which are 1:1 with no copies of the COMMD1 deletion mutations or 1:2 with only one copy of the COMMD1 deletion) Bedlington terriers in the UK are being reported by their vets or breed societies with clear symptoms indicating CT. Some have already been conclusively shown to have CT and we are currently testing the most recently reported of these individuals for the ABCA12 gene. It may be the case that the original cohort of Bedlington terriers with the COMMD1 deletion have been largely removed from the population to be replaced by non- COMMD1 dogs which may be at risk of contracting copper toxicosis.


Should you have a Bedlington terrier whose DNA tests suggest it should not have CT yet it has been diagnosed as in fact having CT we ask your vet to get in touch with Dr Susan Haywood through the breed society or directly with Dr Penny Watson and /or Dr June Swinburne. We shall use the funds made available to us by the BT society to test suspected individuals for COMMD1, ABCA12 and ATP7B. There will be no extra charge. Cambridge vet school will also be available to perform liver biopsy on suspected cases but will have to charge for this at the moment.


 Dr Susan Haywood


 Contact details:


 Dr Penny Watson: pjw36@cam.ac.uk

 Dr June Swinburne: info@animaldnadiagnostics.co.uk

 KC Breed Health Coordinator, BTHG Secretary, Pam Morton: pammorton@postmaster.co.uk.  

      


Following on from last year’s donation to Dr Haywood of £3.000 for a specialised microscope, the BTHG have donated a further £3,500 to help with the cost of the above research.




Copper Toxicosis

Top of Page

Home Page