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:-
Lethargy and depression.
Loss of appetite and the consequential loss of weight and body condition.
Diarrhoea and excessive urination.
Accumulation of fluid in the abdomen.
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.