Molecular diagnosis appended by histopathological signature delineates the white spot syndrome virus (WSSV) infection in penaeid shrimps

Abstract

White spot disease (WSD) occurred by the highly devastating white spot syndrome virus (WSSV) poses a serious impediment toward global shrimp production. We investigated molecular diagnosis and natural infection with WSSV in cultured tiger shrimp (Penaeus monodon) and inspected histopathology of WSD. The incidence of WSSV infection was recorded in six small-scale shrimp farms situated in two districts of Bangladesh, namely Bagerhat and Satkhira. One- and two-step nested polymerase chain reaction models were applied to check the presence of WSSV DNA in shrimp samples. By one-step PCR, 25 of the 36 shrimp samples were WSSV-positive, while the remaining 11 samples were found to be WSSV-negative. After the negative samples underwent a two-step PCR process, only three samples were detected WSSV negative. In Satkhira and Bagerhat districts, the prevalence rates of WSSV infection were 83.33% and 55.56%, respectively, as confirmed by one-step PCR; following two-step nested PCR, the prevalence rates remained unchanged for Satkhira but increased to 100% for Bagerhat sourced samples. One-step PCR was less effective than two-step nested PCR in diagnosing viral infection; instantly evident that the overall prevalence rate rose from 69.44% to 91.67% when switching to two-step nested PCR. In a different experiment, histological analyses of PCR-confirmed WSSV-positive shrimp specimens revealed degenerated tubule lumen and degenerated hepatopancreas with necrosis, while the infected muscle tissues showed muscle fiber fragmentation and separation. Based on effective PCR technique and histopathological evidence of WSSV infection, the study demonstrated the occurrence of WSSV infection in small-scale shrimp farms. The combined practices of the diagnostic tools and information will be useful in understanding the white spot disease and managing its prevention in shrimp production systems.

Keywords

• Virus infection
• Molecular detection
• Prevalence rate
• Histopathological studies
• Shrimp diseases
• Penaeus monodon