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This study evaluated the growth and gut performance of shrimp fed three isonitrogenous diets (37% crude protein) with varying inclusions of fish meal (FM) and soybean meal (SBM): F1 (27.5% FM), F2 (10% FM + 23.5% SBM), and F3 (38% SBM). Over a 28-day period, feed intake, feed conversion ratio (FCR), and survival rates showed no significant differences among the groups. However, shrimp fed F2 and F3 exhibited significantly higher weight gain and average daily growth (ADG) compared to those fed F1 (P < 0.05). Gut performance analysis revealed that F3 consistently had the highest gut passage time (GPT), while F1 had the lowest. By day 28, shrimp fed F2 displayed elevated gut retention time (GRT). F1-fed shrimp showed a high gut passage rate (GPR), whereas F3-fed shrimp had a low GPR until day 21, with differences becoming negligible by day 28. Histological examination of the hepatopancreas revealed an increased R-cell population in shrimp fed F3. These findings highlight the adaptability of shrimp to different dietary compositions and underscore the importance of considering multiple factors when assessing the impacts of feed on growth and physiology., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

The presence of endogenous viral elements (EVE) in the penaeid shrimp genome has been recently reported and suggested to be involved in the host recognition of viral invaders. Our previous report of a search for EVE of infectious hypodermal and haematopoietic necrosis virus (IHHNV-EVE) in the Thai Penaeus monodon whole genome sequence project (GenBank accession no. JABERT000000000) confirmed the presence of three clusters of EVE derived from IHHNV in the shrimp genome. This study aimed to compare an immunohistochemistry method (IHC) and a PCR method to detect infectious IHHNV infection in shrimp. First, specimens collected from farms were checked for IHHNV using three PCR methods; two methods were recommended by WOAH (309 and 389 methods), and a newly established long-range PCR for IHHNV (IHHNV-LA PCR) targeting almost the whole genome (>90%) of IHHNV. Among 29 specimens tested, 24 specimens were positive for WOAH methods (at least one method). Among 24 WOAH-positive specimens (WOAH+), there were 18 specimens with positive IHHNV-LA PCR method (WOAH+/LA+), six specimens with negative IHHNV-LA PCR method (WOAH+/LA-). Six specimens were negative for all methods (WOAH-/LA-). The positive signals detected by IHC method were found only in the specimens with WOAH+/LA+. The results suggest that the WOAH+/LA- specimens were not infected with IHHNV, and the positive WOAH method might result from the EVE-IHHNV. The study recommends combining the IHHNV-LA PCR method and IHC with positive PCR results from WOAH's recommended methods to confirm IHHNV infection., (© 2023 The Authors. Journal of Fish Diseases published by John Wiley & Sons Ltd.)

The microsporidian Enterocytozoon hepatopenaei (EHP) is a major threat to shrimp health worldwide. Severe EHP infections in shrimp cause growth retardation and increase susceptibility to opportunistic infections. EHP produces spores with a chitin wall that enables them to survive prolonged environmental exposure. Previous studies showed that polar tube extrusion is a prerequisite for EHP infection, such that inhibiting extrusion should prevent infection. Using a proteomic approach, polar tube protein 2 of EHP (EhPTP2) was found abundantly in protein extracts obtained from extruded spores. Using an immunofluorescent antibody against EhPTP2 for immunohistochemistry, extruded spores were found in the shrimp hepatopancreas (HP) and intestine, but not in the stomach. We hypothesized that presence of EhPTP2 might be required for successful EHP spore extrusion. To test this hypothesis, we injected EhPTP2-specific double-stranded RNA (dsRNA) and found that it significantly diminished EHP copy numbers in infected shrimp. This indicated reduced amplification of EHP-infected cells in the HP by spores released from previously infected cells. In addition, injection of the dsRNA into EHP-infected shrimp prior to their use in cohabitation with naïve shrimp significantly (p < 0.05) reduced the rate of EHP transmission to naïve shrimp. The results revealed that EhPTP2 plays a crucial role in the life cycle of EHP and that dsRNA targeting EHP mRNA can effectively reach the parasite developing in host cells. This approach is a model for future investigations to identify critical genes for EHP survival and spread as potential targets for preventative and therapeutic measures in shrimp., (© 2024. The Author(s).)