Liver fluke disease Acute fasciolosis There may be an outbreak of the disease following a massive but relatively short–term intake of metacercariae. The high intake is the result of certain seasonal and climatic conditions combined with a lack of fluke control measures; typically, stock forced to graze in heavily contaminated wet areas as a result of overstocking and/or drought. Animals suffering from acute fasciolosis may not show any obvious symptoms. Some animals may show abdominal pain and may become jaundiced. Death is usually due to blood loss resulting from haemorrhage in the liver. The liver haemorrhage is the result of the immature fluke burrowing through the liver. Subacute fasciolosis Subacute fasciolosis is characterised by jaundice, some ill thrift and anaemia. The burrowing fluke causes extensive tissue damage, leading to haemorrhaging and liver damage. The outcome is severe anaemia, liver failure and death in 8–10 weeks. Chronic fasciolosis Chronic fasciolosis is the most common form of liver fluke infection in sheep, goats and cattle – and particularly in more resistant hosts, such as horses and pigs. It occurs when the parasites reach the bile ducts in the liver. The fluke ingests blood, which produces severe anaemia and chronic inflammation and enlargement of the bile ducts. The clinical signs develop slowly. The animals become increasingly anaemic, appetite is lowered, the mucous membranes of the mouth and eyes
become pale and some animals develop oedema under the jaw (‘bottle jaw’). Affected animals are reluctant to travel. Black disease Black disease is an acute and fatal liver disease which can affect sheep and cattle. It is usually associated with the liver damage caused by the migrating young fluke; the damage provides a suitable environment for the germination of spores of Clostridium novyi type B bacteria in the liver.