Surveillance of disease incidence in shrimp farms located in the east coastal region of India and in vitro antibacterial efficacy of probiotics against Vibrio parahaemolyticus

We surveyed 130 shrimp farms located on the eastern coast of India to determine the prevalence of emerging diseases in Litopenaeus vannamei and Penaeus monodon. Live shrimps were collected from the farms based on external symptoms. The biochemical, molecular, and histopathology results confirmed infection with Enterocytozoon hepatopenaei (32.4%), Vibrio parahaemolyticus (27.7%), White Spot Syndrome Virus (25.4%), Vibrio alginolyticus (16.1%), Vibrio harveyi (13.1%), Monodon-type baculovirus (4.61%), and infectious Hematopoietic Necrosis Virus (2.3%) in the collected shrimps. Enterocytozoon hepatopenaei (EHP) occurred more frequently in L. vannamei than P. monodon, with the microsporidian spores in the hepatopancreas. In P. monodon, Monodon-type Baculovirus infection (33.3%) was dominant and small percentages of WSSV, IHHNV, V. alginolyticus, and V. harveyi were observed. A few ponds were observed with co-infection of EHP and WSSV (7.6%), V. parahaemolyticus and WSSV (4.6%) and also V. parahaemolyticus and EHP (6.1%). Among the Vibrio spp, V. parahaemolyticus showed the highest percentage of infection in L. vannamei. Overall, we found that shrimp were chiefly infected with EHP and V. parahaemolyticus. The impact of water quality parameters on shrimp diseases was not addressed in this study. In an antibiotic susceptibility study, V. parahaemolyticus isolated from L. vannamei ponds was susceptible to nitrofurantoin, chloramphenicol, oxytetracycline and tetracycline, but resistant to erythromycin and nalidixic acid. In a preliminary in vitro antibacterial activity assay, probiotics against V. parahaemolyticus showed high inhibitory activity and the results encourage further in-depth studies on the efficacy of probiotics for disease control and prevention in shrimp farms.