Detection of Enterocytozoon hepatopenaei using an invasive but non-lethal sampling method in shrimp (Penaeus vannamei).

The detection of enteric pathogens that cause diseases in shrimp involves the sacrifice of the host to obtain tissue samples for diagnosis. In this study, we describe an invasive but non-lethal sampling methodology using a syringe to collect biopsy samples from the hepatopancreas (HP) of Penaeus vannamei to detect the microsporidian pathogen, Enterocytozoon hepatopenaei (EHP), by qPCR and transmission electron microscopy. EHP was detected in all the infected shrimp by qPCR. The shrimp infected by the microsporidian showed 65% survival at 7 days post-sampling. Transmission electron microscopic examination of the biopsy samples revealed numerous spores of the pathogen. The presence of EHP was further confirmed by histology and in situ hybridization from HP tissue samples. The data shows that a hepatopancreas biopsy could be a viable means of detecting enteric pathogens in shrimp, and the method could be valuable in sampling broodstock and natural populations without the need to sacrifice the animals.

Comparison of four Taura syndrome virus (TSV) isolates in oral challenge studies with Litopenaeus vannamei unselected or selected for resistance to TSV.

Taura syndrome virus (TSV) infection in TSV-resistant (TSR) and TSV-susceptible (Kona) Litopenaeus vannamei (also called Penaeus vannamei) was investigated using histology, in situ hybridization (ISH), conventional reverse transcription polymerase chain reaction (RT-PCR) assays, and SYBR-Green real-time RT-PCR analysis. The shrimp were challenged by feeding with minced tissues of L. vannamei infected with 4 genotypic variants of TSV (Bz01, Th04, UsHi94, and Ve05). Survival probabilities of TSR shrimp were higher than those for Kona shrimp with all 4 variants. Th04, UsHi94, and Ve05 gave no Taura syndrome lesions with TSR shrimp. In contrast, TSR shrimp challenged with Bz01 and Kona shrimp with all 4 TSV variants exhibited severe necrosis of cuticular epithelial cells and lymphoid organ spheroids, indicative of acute and chronic phases of TSV infection, respectively. TSV was not detected by RT-PCR in TSR shrimp infected with Th04, UsHi94, and Ve05, or in Kona shrimp infected with Ve05 but was detected in TSR shrimp infected with Bz01 and in Kona shrimp infected with Bz01, Th04, and UsHi94. Real-time RT-PCR revealed that mean TSV copy numbers in TSR shrimp infected with Bz01, Th04, and UsHi94 were significantly (p < 0.0005) lower than those in Kona shrimp. In contrast, mean TSV copy numbers in TSR and Kona shrimp infected with Ve05 were not significantly different (p > 0.4). The results show that TSR L. vannamei are susceptible to infection but give high survival rates following challenge by all 4 variants of TSV.