In vitro and in vivo efficacy of anthelmintic compounds against blood fluke (Cardicola forsteri)

Blood fluke, Cardicola forsteri, infects Southern Bluefin Tuna, particularly during ranching. Efficacy of four anthelmintics was tested against this parasite. There was an agreement between in vitro and in vivo results. Praziquantel was the only effective anthelmintic. It was the most potent anthelmintic in decreasing fluke responsiveness in vitro, with concentrations ranging between 1.5 μg/mL and 200 μg/mL stopping adult fluke response within less than 5 min. In vivo, both the higher (150 mg/kg) and the lower (75 mg/kg) dose praziquantel treatment resulted in a significant reduction of the number of flukes present in the hearts. A significant effect of treatment on the mean number of blood fluke eggs per cm² of tuna myocardium was observed, with fish treated with either of the two doses of praziquantel having at least 6 times lower numbers of eggs in their hearts. Control fish and fish treated with praziquantel (both doses) and lower dose Closal had very low average number of eggs per cm² of gill and were significantly lower than in fish treated with fenbendazole. While this research shows that praziquantel is the treatment of choice against blood fluke, C. forsteri, further research is needed to determine optimum dose, best treatment application method, palatability and any potential side effects.