Copper toxicosis in Labrador Retrievers

Copper toxicosis in Labrador Retrievers

Copper toxicosis, also known as copper accumulation or Wilson’s disease, is a common condition in Labrador Retrievers. This disorder results from excessive copper storage in the liver, leading to chronic liver inflammation (Copper Associated Hepatitis, CAH) and a range of serious health issues.

What is copper toxicosis?

Copper is absorbed from food through the intestines and serves important roles throughout the body. Normally, this process is tightly regulated, ensuring that the body absorbs just enough copper while excreting any excess via bile. However, in dogs with copper toxicosis, this balance is disrupted, and too much copper is stored in the liver.

How does copper toxicosis develop?

The copper levels in the body are influenced by several factors, including dietary copper intake, hereditary DNA mutations, and other (partly unknown) factors.

Currently, three DNA mutations can be identified with a genetic test: ATP7A (test code H824), ATP7B (Wilson’s disease, test code H825), and RETN (test code H662). These genes work together, with ATP7B being the most significant. When functioning properly, the ATP7B gene helps eliminate excess copper through bile. However, mutations in this gene cause copper to build up in the liver. Both carriers (dogs with one copy of the mutation) and affected dogs (with two copies of the mutation) are at risk of copper accumulation, with affected dogs being at the highest risk. The ATP7A and RETN genes, on the other hand, are protective and may reduce the risk of copper accumulation in dogs with ATP7B mutations.

Symptoms of copper toxicosis

Symptoms usually emerge only after substantial liver damage has occurred due to inflammation caused by the copper buildup. Over time, this leads to irreversible liver cirrhosis. Symptoms often mimic those of chronic liver disease, including lethargy, decreased appetite, vomiting, jaundice, and fluid buildup in the abdomen.

When copper toxicosis is diagnosed at the stage of chronic liver failure (cirrhosis), treatment options are typically limited. In such cases, the dog’s prognosis is poor, and the chronic liver failure will often be fatal. This highlights the importance of early detection and intervention.

On average, Labrador Retrievers are diagnosed with copper accumulation at around six years of age, though the range can vary from 2 to 12 years. Treatment typically involves medication and dietary changes. The effectiveness of treatment depends on how early the condition is caught and how the dog responds to the prescribed therapy.

Preventing copper toxicosis

Because many factors contribute to copper accumulation, complete prevention isn’t possible. However, the risk can be significantly reduced through genetic testing. Labrador Retrievers can be screened for the ATP7B mutation (linked to Wilson’s disease) using a simple cheek swab. Breeders can then make informed decisions to avoid producing puppies with two copies of the ATP7B mutation, which would greatly reduce the likelihood of severe copper accumulation. This is achieved by avoiding the mating of two carriers or affected dogs.

In addition, modifier genes ATP7A and RETN can help lower liver copper levels, reducing both the risk and severity of copper accumulation in dogs with ATP7B mutations. While the protective effect of ATP7A is well established, research is still ongoing regarding the specific effects of RETN. These genes do not influence copper metabolism in dogs without ATP7B mutations. Therefore, it’s advisable to test Labradors for all three genes. Dogs carrying ATP7A or RETN mutations typically show no adverse symptoms and can safely be used for breeding.

My Labrador is a carrier or affected by Wilson’s Disease (ATP7B) – What should I do?

The accumulation of copper is multifactorial, and dogs with one or two copies of the ATP7B mutation are at increased risk. Labrador Retrievers with ATP7B mutations and one or two copies of the modifier genes (ATP7A and/or RETN) also face an elevated risk of copper buildup compared to those without the ATP7B mutation.

Not all dogs with ATP7B mutations will develop copper accumulation and copper toxicosis or show elevated liver values, but it’s beneficial to regularly monitor their liver function through blood tests (especially alanine aminotransferase, ALT). If liver values rise, a liver biopsy may be necessary to confirm copper accumulation. This method, while more invasive, is more reliable than blood tests and can also be used for early screening. Furthermore, the copper-to-zinc ratio in the diet can influence copper levels in affected dogs, so it’s essential to discuss an appropriate monitoring and dietary plan with your veterinarian. By using these genetic tools and working closely with your veterinarian, you can help manage and reduce the risks associated with copper accumulation in your Labrador Retriever.

Does copper toxicosis also occur in other dog breeds?

In addition to Labrador Retrievers, other dog breeds can also be genetically predisposed to copper accumulation and copper toxicosis. Two such breeds are the Doberman and the Bedlington Terrier, both of which have specific DNA tests available for copper toxicosis.

In Dobermans, copper toxicosis is caused by the same ATP7B mutation found in Labrador Retrievers. Meanwhile, in Bedlington Terriers, the condition is linked to a different mutation in the COMMD1 gene (also referred to as MURR1). Although Wilson’s disease can occur in both breeds, the copper toxicosis modifier genes ATP7A and RETN, which play a protective role in Labradors, do not influence the occurrence of copper toxicosis in these breeds.

For Dobermans, it is recommended to test solely for the ATP7B mutation (test code H825) to assess the risk of developing copper accumulation and toxicosis. For Bedlington Terriers, testing for the COMMD1 mutation (test code H701) provides insights into their risk of the disease. Testing for these specific gene mutations in each breed can help prevent copper-related health issues and guide responsible breeding practices.

Relevant tests

The three copper accumulation-related DNA tests are included in the CombiBreed package for Labrador Retrievers (test code H323), another available option that focuses exclusively on these tests is Copper Toxicosis (test code H288).