Cases of chronic weight loss and diarrhoea of individual cows warrant investigation, in part because the differential diagnosis includes bovine Johne's disease and other diseases of herd significance such as internal parasitism and fasciolosis.
In this case of chronic weight loss and diarrhoea the cow was found on necropsy to be suffering from a hepatic carcinoma.
The cow, one of about forty Angus and Murray Grey cows running in a commercial herd near Tarana, about 40 km east of Bathurst was first examined on 25 September 2013 (M13-14620) with a history of diarrhoea and weight loss over several months. The cow was sero-negative for BJD, but she continued to lose weight and was euthanased.
The mature cow was emaciated. The mucous membranes and internal tissues were jaundiced. The liver was markedly enlarged with yellow fibrinous sheets on the diaphragmatic surface, and raised circular masses visible on the diaphragmatic surface. On cut surface, numerous discrete to coalescing pale tan masses from 2 cm to 10 cm diameter were seen (Figure 1). Some large cavities within the liver were filled with necrotic material.
There is bile in the cytoplasm of the proximal convoluted tubules consistent with jaundice. There were many large nuclei in the cells of the proximal convoluted tubules, some bordering on megalocytosis. This could be a reflection of chronic insult to kidney for example from chronic toxic plant exposure, but this may be physiological rather than pathological.
The hepatic nodules were morphologically typical of bovine hepatocellular carcinoma. The tumours had compressed other structures including bile ducts eliciting some bile duct proliferation and attempted circumferentiation of the space occupying lesion. There was compression and focal necrosis of hepatic lobules and some hepatocellular proliferation and hypertrophy.
Hepatobiliary tumours are fairly common in livestock, second only to lymphomas as the most common visceral tumours in cattle, sheep, cats and dogs. Bovine hepatocellular carcinomas can be divided into various groups based on morphology. In a retrospective study of 66 cases of primary hepatic neoplasms by Bettini and Marcato (1992), 40 were hepatocellular carcinomas and 10 were hepatocellular adenomas.
In this case, the kidney changes suggest there may be significant exposure to some toxic principles. Aflatoxins are associated with hepatocellular carcinomas and there is evidence of an association of pyrrolizidine alkaloids with hepatocellular carcinomas, at least in some species (Bettini and Marcato, 1992). In this case, the cow had a history of grazing pastures infested with Paterson's curse (Echium plantagineum) and was fed hay (potentially containing aflatoxins) during a drought 5-6 years previously.