Vibrio load and percentage composition of sucrose-fermenting vibrios in Nile tilapia (Oreochromis niloticus) cultured in brackish water earthen ponds and biocontrol potential of recycled tilapia-conditioned greenwater against population growth of V. parahaemolyticus and non-sucrose-fermenting vibrios in the grow-out culture of white leg shrimp (Litopenaeus vannamei)

Abstract

<i>Vibrio</i> are known opportunistic pathogens of pond-cultured fish and shrimp. This study determined the presumptive <i>Vibrio</i> count (PVC) and percentage composition of “beneficial” sucrose-fermenting vibrios (SFVs) and “pathogenic” non-SFVs in the water, sediment, gills and intestines of healthy tilapia <i>Oreochromis niloticus</i> collected every 2 weeks from Days 30 to 120 post-stocking in brackish water earthen ponds. PVCs in water and sediment ranged from 10²–10⁴ CFU/ml/CFU/g while in tilapias' gills and intestines, PVCs ranged from 10³–10⁶ CFU/g and 10²–10⁶ CFU/g, respectively, with SFVs dominating in water, sediment, gills (≥50%), and intestines (≥80%) of tilapia. Because use of tilapia-conditioned green water (TCGW) for shrimp's grow-out culture has been reported effective against acute hepatopancreatic necrosis disease outbreaks caused by <i>V. parahaemolyticus</i>, PVC, SFVs/non-SFVs (%), and <i>V. parahaemolyticus</i> count (VPC) in the recycled TCGW and <i>Litopenaeus vannamei</i>'s hepatopancreas were also examined from stocking until 105 days of culture (DOC) in earthen ponds. PVCs ranging from 10²–10³ CFU/ml and 10³–10⁴ CFU/g were noted in water and shrimp's hepatopancreas, respectively. While non-SFVs population in water varied, a downward trend typified by an abrupt 50% reduction was noted in hepatopancreas at DOC 42, and remained or further dropped until DOC 105. VPCs in water likewise varied (undetectable–10² CFU/ml) while in hepatopancreas, counts dropped to undetectable level from DOC 70 onwards. Current data illustrate that remarkable shift of SFVs' dominance in the water and concomitantly in shrimp's hepatopancreas, plays a pivotal role in regulating non-SFVs proliferation in shrimp's hepatopancreas via competitive exclusion.