Immunostimulant effect of nucleotide supplementation on shrimp Penaeus vannamei submitted to bacterial challenge with Vibrio parahaemolyticus

Aim of the study: Vibriosis and other bacterial infections significantly challenge Pacific white shrimp (Penaeus vannamei) production. This study evaluated the immunostimulant effect of nucleotide supplementation on hemato-immunological parameters, digestive gland morphology, presumptive Vibrio count, and survival of Penaeus vannamei exposed to Vibrio parahaemolyticus. Area of study: Aquaculture nutrition and health management, specifically focusing on the mitigation of bacterial disease (Vibriosis) in cultured Pacific white shrimp. Material and methods: Three nucleotide supplementation levels were evaluated: NT75 (75 mg/kg), NT150 (150 mg/kg), and NT300 (300 mg/kg), alongside a control group (C). After 60 days of feeding the experimental diets, the shrimp were challenged by immersion in a bacterial suspension of Vibrio parahaemolyticus (106 CFU mL-1) for 30 days. Mortality and clinical signs were monitored, and hemato-immunological, histological, and bacteriological parameters were analyzed. Main results: Nucleotide-supplemented treatments exhibited improved growth performance and reduced pre-challenge mortality. Following the bacterial challenge, all treatments showed an acute, albeit non-significant, change in total and differential hemocyte counts. However, histological analysis of the digestive gland revealed severe lesions, including tubule deformities and necrosis, across all treatment groups. On days 5 and 15, significant differences in Vibrio sp. counts within the digestive gland were observed. Specifically, differences were noted between Control (C) and NT75, and between NT75 and NT300, indicating varying bacterial colonization over time. Research highlights: Higher nucleotide supplementation levels improved shrimp performance, reduced pre-challenge mortality, and enhanced the acute immune response following a bacterial challenge, suggesting their utility as an effective immunostimulant against Vibriosis.