Pathological findings in southern bluefin tuna, Thunnus maccoyii (Castelnau), infected with Cardicola forsteri (Cribb, Daintith & Munday, 2000) (Digenea: Sanguinicolidae), a blood fluke

Gills, heart ventricles and a limited number of other organs were collected from wild and captive southern bluefin tuna, and examined histologically for eggs of Cardicola forsteri. A limited number of entire hearts from farmed tuna were also examined, some of which yielded adult flukes within the ventricles. No adult flukes or their eggs were found in wild tuna. In infected farmed fish, fluke eggs impacted in the afferent filamentary blood vessels where they provoked a marked, but variable, inflammatory response, resulting in nodular gill lesions. No eggs were found on the efferent side of the gill vasculature, or in the compacta of the ventricle, which is supplied with blood from coronary vessels. The infection does not appear to cause mortality in farmed tuna.