Blood fluke promotes mortality of yellowtail caused by Lactococcus garvieae

Abstract

Yellowtail Seriola quinqueradiata were placed in an enzootic area of blood fluke infestation. Subsequently, the fish were challenged with the bacterial fish pathogen Lactococcus garvieae. The final cumulative mortality by L. garvieae was significantly higher in the blood fluke-infested fish than in the uninfested fish. The rate of the number of the gill filaments harboring the parasite eggs in the dead fish was significantly higher than that of the surviving fish, and among the dead fish, the fish with the higher rate died in a shorter time. These results suggest that the blood fluke infestation promotes the mortality by L. garvieae infection in yellowtail.