First incidence of loose-shell syndrome disease in the giant tiger shrimp Penaeus monodon from the brackish water ponds in Bangladesh

The recent incidence of loose-shell syndrome disease (LSSD) in grow-out shrimp ponds appears to be a major problem in Bangladesh. Therefore, the aims of our study were (i) to observe clinical signs of LSSD to confirm its incidence and (ii) to identify the probable causative agents for LSSD in shrimp. Sampling was conducted randomly from five LSSD-affected ponds and three non-affected ponds near Bakkhali River; ecological parameters were measured. A total of 180 healthy shrimps were used for this experiment, where LSSD-affected shrimp extracts were either injected into the shrimps or mixed with water in the experimental tanks. Finally, microbial examinations were performed to identify the possible LSSD causative agents from the infected individuals. The total shrimp production was higher in ponds with healthy populations (185 kg/ha) than from LSSD-affected ponds (126-146 kg/ha); the survival rate of shrimp at harvest was significantly different (p<.01) between normal and LSSD-affected ponds. The prevalence of infection with white spot syndrome virus (WSSV) and monodon baculovirus (MBV) was found to be lower than that of the Vibrio infections. During the investigation, 8% of LSSD-affected individuals were WSSV positive and 5% were MBV positive, and 4% were infected by both. Our study suggested that the prevalence of LSSD in tiger shrimp might be associated with multiple Vibrio bacterial infections, poor soil and water quality, as well as poor pond management.