Schistosoma mattheei in the ox: the chronic hepatic syndrome.

A Friesland steer infested on four occasions at intervals of 4--6 weeks with 20 000 cercariae of Schistosoma mattheei developed progressive hepatic failure and died after 74 weeks. The condition was characterised by enlargement and induration of the liver with portal fibrosis, inflammation of the portal veins and "piecemeal necrosis", and was associated with a severe circulating eosinophilia and hypergammaglobulinaemia. Similar cases were encountered in two natural outbreaks. The syndrome is considered to be of immunological origin, initiated by the reaction in the portal veins to antigen from schistosomes killed by the immune response of the host. It is usually seen in animals exposed to repeated heavy infestation but may occur occasionally after light infestation.