West Highland White Terrier ©The Kennel Club

Copper is an essential nutrient, stored in the liver, which is necessary in small quantities for health, but is toxic in high amounts. Copper toxicosis results from copper build-up in the liver as a result of an interaction between a dog’s genetic risk and its environment: predominantly the copper concentration of the diet. Any dog fed a very high amount of copper will develop copper toxicosis but some known and also likely unknown genetic factors increase the risk with lower dietary copper concentrations. The most well described inherited predisposition is in Bedlington terriers which can be affected with what is known as the COMMD1 deletion. This single mutation makes them very susceptible to copper toxicosis, particularly if they carry two copies. Other genetic mutations have been described both in Bedlington terriers and in other breeds which increase the dog’s susceptibility to copper storage disease but have a less marked effect, ie only contribute a small amount to the disease, suggesting there may be other genetic and environmental factors involved. Copper content of the dog’s diet will be one of these. Some dog foods (both manufactured and home-made) contain high concentrations of copper but this is often not well described on labels or easy to calculate. The high levels of copper in the liver which build up as a result of genetic predisposition and diet cause damage to the liver cells resulting in further inflammation of the liver and death of liver tissue, ie chronic hepatitis. If not recognized and treated, in the longer term, this often results in end stage scarring known as cirrhosis.

In the early stages of disease there are no signs, but results of liver related blood tests are usually abnormal. Signs are more likely to develop in older dogs and affected dogs are usually older than 1 year when the disease is first noticed. The signs are often vague at the start with depression, weight loss and picky appetite being common. Vomiting and diarrhea may develop along with excessive drinking as liver function becomes reduced. As the liver function is further reduced then signs of liver disease develop such as jaundice (yellowing around the eyes and gums), fluid build-up in the abdomen and neurological signs such as depression and head pressing due to the effect of toxins on the brain.

Your veterinarian may have a suspicion of copper toxicosis based on the history and your dog’s breed. Blood and urine samples may show signs of liver damage and reduced liver function. An ultrasound of the liver will probably be advised to rule out other obvious causes of increased liver enzymes such as gall bladder disease. If your veterinarian thinks your dog might have copper toxicosis they may need to take a biopsy of the liver to look for inflammation and to measure the copper levels. Copper toxicosis cannot be diagnosed accurately or treated effectively without a biopsy. Genetic tests alone do not rule in or out copper toxicosis.

Yes – and the sooner the treatment is started, the better. Treatment usually relies on a combination of a low copper diet (to stop any further copper build-up) and the use of drugs called chelators which remove the copper from the liver, together with anti-oxidants to reduce the damage caused by the copper in the liver. The body only has a requirement for a very small amount of copper and most of the copper from the diet normally passes out of the body again. Affected dogs have trouble processing normal or increased amounts of copper in the diet. To prevent build-up of copper in the liver of affected dogs, dietary intake of copper is restricted. There are a number of specialist low copper veterinary diets available or home cooked diets can be prepared with the advice of a veterinary nutritionist. Tit bits high in copper should be avoided such as nuts, shell-fish, offal (including liver) and whole wheats. In some areas (depending on your water supply) dogs may need to be given bottled water. Your veterinarian will probably also advise the use of an agent that binds to copper and helps it to be removed from the body (copper chelator). The most common agent used is penicillamine. This agent is not currently licensed for use in dogs, but we have many decades of experience using it. Your veterinarian will explain the potential benefits and risks. Dogs may feel sick when they first start the drug, but this can often be ameliorated by an initial dose reduction or giving with a little food which you should discuss with your veterinarian. It is worth persevering as chelation can be very effective. Antioxidants are also often prescribed such as vitamin E and S-adenosylmethionine. Other treatments may be prescribed including liver support drugs, eg ursodiol. Zinc supplements are also sometimes prescribed after successful chelation. It usually takes at least 6 to 12 months of chelation to remove the copper from the liver but the good news is that the liver damage can at least be partially reversed if treatment is successful. Progress will be monitored with regular blood tests and ideally a liver biopsy at the end of the treatment period, although many owners elect not to have this. Some dogs can then stop chelation whereas others need it life long and it is prudent to continue a low copper diet for the rest of your dog’s life.

The disease and how it is inherited has been well studied in Bedlington terriers and there is a DNA test available for the most important mutation associated with copper storage disease in the breed (COMMD1 deletion). Dogs carrying the abnormal gene should ideally not be bred from. If you are thinking of buying a Bedlington terrier, make sure you know the results of DNA testing in both parents. If there is any risk your puppy is carrying the gene, you should consider feeding a low copper diet from an early age and discuss this with your vet. However, recent studies have identified Bedlington terriers with copper toxicosis which are not carrying the COMMD1 mutation, so unfortunately freedom from this mutation is not a guarantee of freedom from the disease. There is also a DNA test available (known as ATP7B) for Labradors and Dobermanns which may help to guide whether a dog is at risk of copper toxicosis. However, the inheritance of disease in these breeds is not straightforward and many factors can determine whether or not a dog actually becomes ill. Genetic testing is not routinely carried out before breeding in dogs in these breeds and will not accurately identify the risk of disease in an individual pet dog.