Copper Toxicosis

Note - Copper toxicosis may alternatively be referred to as Copper Storage Disease, Copper Storage Hepatitis, Copper Hepatoxicosis or Hepatic Copper Toxicosis

Introduction

Copper is one of several essential elements that are necessary for survival and must be provided in the dogs diet but only in relatively 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:

It is a constituent (as a co-factor) of many enzyme systems.

It is closely linked with iron metabolism. A deficiency of copper can result in a form of anaemia which can occur even when the animal’s intake of iron is normal.

Copper is essential for the formation of collagen fibres and a deficiency can result in bone/joint disorders.

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 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 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. 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.

Copper toxicosis in Bedlington terriers was first reported in 1975 in the USA and since then it has been recognised in a number of other countries. It was established later that the form of the disease found in Bedlington terriers is a genetic disorder. In order for the condition to develop in a dog/bitch a copy of the 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 Disease.

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.

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:-

Lethargy and depression.
Loss of appetite and the consequential loss of weight and body condition.
Excessive thirst.
Intermittent vomiting.
Diarrhoea and excessive urination.
Accumulation of fluid in the abdomen.
Jaundice.
Nervous symptoms may also be observed.

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.

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.

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.

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.

A DNA test (the COMMD1 test) was developed and was introduced by the Animal Health Trust in July 2005.

However, evidence has accumulated over time that supported the speculation that a second gene may be involved. Current research has found a probable 2nd gene but no test is yet available. Good progress has been made and it is hoped a further test will be available in the future.

The Research into Copper Toxicosis in Bedlington Terriers continues.

Although we do recommend that all Bedlingtons should be tested using the COMMD1 test, it is important to understand that this is not 100% conclusive for Copper Toxicosis in Bedlington Terriers. The only definitive test is a liver biopsy which is invasive surgery and cannot be performed before a dog is 12 months old. Every biopsy can help the research to progress, but this should be discussed with the experts in advance of any surgery.

Treatment of affected dogs.

If a definitive diagnosis has been made by your vet, treatment can be offered to include a low copper diet, which can be commercial or home made. The veterinary surgeon should be able to advise on suitable ingredients and the formulation of a diet, including the type of mineral/vitamin supplements.

If clinical signs are evident, chelating agents might be prescribed by your vet. These function by binding to copper so that it can be excreted in the urine. Chelating agents also have an anti-inflammatory effect, which may help to reduce cirrhosis i.e. fibrous tissue which is formed in chronic disease and further impairs the liver function.

Other treatments your vet may recommend to support liver function include: Milk Thistle, Antioxidants, Antibiotics, Steroids, Anti-inflammatory drugs and other medication to support immunity.