Molecular detection of pathogens from cultured whiteleg shrimp farms in Karnataka, India

Abstract

Litopenaeus vannamei, commonly known as the Whiteleg shrimp, emerges as one of the most economically lucrative species in India's commercial aquaculture sector. The primary objective of this study is to detect common pathogens affecting cultured shrimp in Karnataka using polymerase chain reaction (PCR) analysis. Over the period spanning from January 2020 to March 2022, a total of 278 samples were meticulously collected from shrimp farms in Karnataka. The screening process targeted both Office of Internationale des Epizootics (OIE) listed and non-OIE listed shrimp pathogens. The PCR analysis revealed the presence of white spot syndrome virus and Enterocytozoon hepatopenaei in the collected samples, with no detection of other pathogens. Out of the 278 samples, 63 (22.6%) were confirmed positive for EHP, while 14 (5%) showed infection by WSSV. Intriguingly, three samples were concurrently infected by both EHP and WSSV. Shrimp samples infected with WSSV exhibited distinctive white spots on the carapace, whereas EHP-infected shrimps displayed symptoms such as size variation and a white gut. Further histopathology analysis of gill tissue infected with WSSV revealed basophilic intra-nuclear inclusion bodies, while hepatopancreas tissue infected with EHP exhibited basophilic plasmodium. Notably, the study underscored a higher prevalence of EHP in shrimp farms across Karnataka. In light of these findings, the study strongly advocates for the implementation of stringent biosecurity measures and robust management practices in shrimp culture areas, emphasizing their critical role in sustaining the cultivation of L. vannamei in India.