Effects of the modified Huanglian Jiedu decoction on the disease resistance in grey mullet (Mugil cephalus) to Lactococcus garvieae

Abstract Lactococcosis is prevalent on grey mullet ( Mugil cephalus ) in Hong Kong aquaculture resulting in serious economic loss. A compound formulation of Traditional Chinese Medicines (TCM) (modified Huanglian Jiedu decoction (HLJDD)) comprising Rhizoma coptidis , Radix scutellaria , Cortex phellodendri , Fructus gardeniae , Fructus forsythiae and Flos lonicerae japonicae (in a ratio of 3:2:2:3:3:5) were applied as feed supplements to deal with the disease. The Nitroblue tetrazolium activity in blood, bactericidal activity and total immunoglobulin in plasma were significantly enhanced after feeding 1% of this TCM for 28 days. The disease resistances to Lactococcus garvieae in 1% and 2% TCM feeding groups were significantly enhanced. In the in vitro study, the modified HLJDD also activated the plasma bactericidal activities ( p . 01). Based on this study, 1% modified HLJDD feeding for 28 days may be an optimal dose to prevent L. garvieae infection and could be used in aquaculture industries.