Efficacy of ‘CIBA EHP Cura I' in the control and treatment of Ecytonucleospora hepatopenaei in shrimp culture

Abstract

Ecytonucleospora hepatopenaei (EHP), a eukaryotic microsporidian parasite, causes huge economic losses in many shrimp-farming nations. However, effective prophylactics and therapeutics for EHP management are very limited. In this study, a phytobiotic-based therapeutic was found to be effective in controlling EHP and was named ‘CIBA EHP Cura I' (Cura). Drugs such as metronidazole (Met), tinidazole (Tin), albendazole (Alb), nifedipine (Nif), ketoconazole (Ket), verapamil (Ver), and plant derivatives such as carvacrol (Car) along with Cura were evaluated against EHP. Though all the drugs significantly reduced EHP load, they cause severe necrosis, degeneration and black discolouration in shrimp hepatopancreas except for Cura. While, the shrimp fed with Cura showed a largely normal hepatopancreas without any degenerative changes. Also, all the other drugs except Cura largely failed to increase the growth and survival of shrimp. At 0.1 %, the Cura was found to completely inhibit the EHP spore germination in vitro. In further experiments, the EHP-challenged shrimp (n = 25 in triplicate) were fed with feed top coated with Cura (0.05 %, 0.1 %, 0.15 % and 0.2 %) and reared for 60 days. The shrimp group fed with Cura at 0.1 %, 0.15 % and 0.2 % exhibited significantly higher innate immune activity (catalase, phenol oxidase and total haemocyte count) and significantly higher weight gain and survival rate. Cura, at 0.15 %, exhibited higher performance across all the treatments. Cura showed strong binding affinity with multiple targets such as SWP, ADP/ATP carrier, protein kinase, and endochitinase of EHP in silico. Additionally, Cura demonstrated potent antibacterial activity against Vibrio parahaemolyticus. Thus, this study highlights Cura, as a promising phytobiotic-based therapeutic for the effective EHP management.