Use of an essential oil blend formulation (EOBF) as an effective disinfectant against pathogenic luminescent vibrio bacteria

Vibrio bacterial groups, mainly Vibrio harveyi, V. campbellii, V. parahaemolyticus and V. splendidus, are considered highly pathogenic to shrimp larvae. These bacteria become more aggressive and lethal in their luminescent form due to their quorum sensing characteristics. An effort was made to minimize the luminescent Vibrio load using an essential oil blend formulation (EOBF) consisting of Eucalyptus oil, jasmine oil, and gardenia oil in equal proportions. An eighteen-day small hatchery-scale trial was initiated, starting from the nauplii stage. The shrimp were distributed into three groups: a T-1 negative control with four replicates, a T-2 positive control with four replicates, and an EOBF treatment group with eight replicates, which was subgrouped equally into two rooms, named T-3 and T-4. The shrimp at the mysis stage were challenged using a sublethal dose of 103 CFU/mL luminescent Vibrio. Vibrio observations, physical properties of tank water and shrimp productivity were measured. The obtained results indicated that the EOBF-treated group had better productivity than the positive control group. The positive control T-2 performance at the time of harvest (PL 10 stage) was as follows: survival rate 67.57%, length 9.01 mm, size variation 12.62, mean body weight 4.51 mg and biomass 116.36 g. The performance of EOBF groups T-3 and T-4 at the time of harvest (PL 10 stage) was as follows: survival rate 56.34%, length 10 mm, size variation 10.21, mean body weight 7.71 mg and biomass 155.38 g. The EOBF group was better in terms of length, size variation, mean body weight and biomass. The presence of harmful Vibrio in tank water, recognized as green colonies cultured on TCBS agar, was almost one log lower in the EOBF group than in the positive control. The presence of pathogenic luminescent Vibrio was observed by the wet mount method, which showed that the incidence rate in the positive control (T-2) was 45%, whereas it was 19% in the EOBF group. The results of this trial suggest that EOBF can reduce pathogenic Vibrio in hatchery environments and can increase productivity.