Enterocytozoon hepatopenaei (EHP) Infection Alters the Metabolic Processes and Induces Oxidative Stress in Penaeus vannamei

SYNLAC Prime probiotics alleviate Enterocytozoon hepatopenaei-induced damage in white shrimp, Penaeus vannamei by enhancing growth, immunity, and resistance to Vibrio parahaemolyticus

This study evaluates the efficacy of SYNLAC Prime probiotics, both live and heat-killed, in alleviating growth retardation and enhancing the health of white shrimp, Penaeus vannamei infected with Enterocytozoon hepatopenaei (EHP). Probiotic supplementation significantly improved growth performance of EHP-infected shrimp by increasing digestive enzyme activity in the hepatopancreas and guts. Interestingly, the final weight and weight gain percentage of EHP-infected shrimp supplemented with live probiotics surpassed that of healthy control shrimp. Probiotics modulated the gut microbiota, notably reducing Vibrio abundance. The immunomodulatory effects of probiotics were further highlighted by increased expression of immune-related genes and enhanced immune parameters. These immune responses are critical for pathogen defense and may contribute to the observed reduction in EHP load and increased resistance to Vibrio parahaemolyticus infection. To elucidate the metabolic differences between healthy and EHP-infected shrimp and to assess the effects of dietary probiotic supplementation, hepatopancreatic metabolite profiles were analyzed using LC-MS/MS. In positive ion mode, 54, 76, and 84 differential metabolites were identified in the NCON, P5D, and P5L groups, respectively, relative to the PCON group. In negative ion mode, 89, 80, and 64 metabolites were significantly altered across the same comparisons. KEGG pathway enrichment indicated that differential metabolites were primarily involved in key metabolic pathways, including terpenoid backbone biosynthesis, one-carbon metabolism, glycolysis/gluconeogenesis, pyrimidine metabolism, and amino acid biosynthesis. Notably, probiotic supplementation modulated multiple metabolic pathways associated with host immunity and energy metabolism. Heatmap analyses further revealed distinct metabolite expression patterns across all experimental groups. Overall, the findings demonstrate that probiotics, particularly live strains, offer a promising intervention for mitigating EHP-induced growth impairment and disease, enhancing both immune responses and metabolic stability in shrimp. This highlights the potential of probiotics as an effective tool in shrimp aquaculture, not only to improve growth performance but also to manage infections and improve overall health.

Tissue and cell types infected by Ecytonucleospora hepatopenaei (EHP)

Ecytonucleospora hepatopenaei (EHP) is a microsporidian pathogen causing significant losses in shrimp aquaculture worldwide. The hepatopancreas is recognized as the primary target tissue, but the broader tissue and cell tropism of EHP and its ability to infect other components of the digestive system or non-digestive tissues remain unclear, especially when infections are intense and the host physiology is compromised. This study aimed to comprehensively investigate the histopathology of EHP infections in severely infected Penaeus vannamei to determine its tissue and cell tropism and assess the potential for systemic infection. The severity of infection was graded based on hepatopancreatic lesions. Histopathology showed that EHP spores were distributed in the digestive system of heavily infected shrimp, but not in non-digestive tissues such as gills, heart, gonad, nerves or skeletal muscle. EHP only infected the epithelial cells of the hepatopancreas, midgut, and midgut caeca, which lack the protective chitin layers. While the epithelial cells of the esophagus, stomach and hindgut were unaffected due to the protection of the inner chitinous layer, despite the presence of large numbers of EHP spores in these regions. Histopathology and ultrastructural pathology demonstrated that the R (reserve), F (fibrillar), B (blister), E (embryonic) and M (small midget) cells of the hepatopancreas were infected. These findings indicate that EHP does not cause systemic infection and has a strict cell tropism for the epithelium in the shrimp host.

Characterization of Enterocytozoon hepatopenaei infection stages in shrimp using machine learning and gene network analysis

Enterocytozoon hepatopenaei (EHP), causing hepatopancreatic microsporidiosis (HPM), significantly impacts Litopenaeus vannamei, leading to economic losses. Using bioinformatics and machine learning, this study characterized EHP infection stages and host-pathogen interactions. Consensus clustering of 2,613 metabolism-related genes from 36 shrimp samples identified four subclasses: healthy (HG), heavily (HEG), moderately (MEG), and lightly infected groups (LEG). Gene Set Variation Analysis (GSVA) revealed subclass-specific metabolic and immune patterns, with HEG showing impaired carbohydrate metabolism and upregulated amino acid degradation, MEG indicating recovery, and LEG demonstrating metabolic normalization. Weighted Gene Co-expression Network Analysis (WGCNA) linked infection subclasses to pathways like Hippo, JAK-STAT, steroid biosynthesis, and calcium signaling. Machine learning identified 52 characteristic genes involved in EHP proliferation (e.g., RAPTOR), host invasion (e.g., cell surface glycoprotein 1), and host defense (e.g., mucin-5AC). A stacked classifier model predicted infection severity with high accuracy. EHP severely impacts immunity, autophagy, and oxidative stress in early infection, with host responses evolving from detoxification to metabolic recovery and adaptation. Key pathways and genes, including polar tube protein (PTP) and mucin-5AC, were identified as critical to host-pathogen interactions, offering insights into EHP infection dynamics and potential intervention strategies.

Comparative evaluation of three herbal extracts on growth performance, immune response, and resistance against Vibrio parahaemolyticus in Litopenaeus vannamei

This study evaluated the effects of dietary supplementation with herbal extracts from Artemisia herba-alba, Lonicera japonica, and Lilium candidum on growth performance, survival, feed utilization, antioxidant capacity, and immune response in Litopenaeus vannamei. The efficacy of these herbal-supplemented diets was assessed in enhancing resistance against Vibrio parahaemolyticus-induced Acute Hepatopancreatic Necrosis Disease (Vp AHPND). A total of 2,400 shrimp post-larvae (initial weight 0.74 ± 0.02 g) were randomly assigned to four triplicate groups. Shrimp were fed isonitrogenous and isocaloric diets: T1 (control, basal diet), T2 (basal diet + 250 mg/kg A. herba-alba), T3 (basal diet + 250 mg/kg L. japonica), and T4 (basal diet + 250 mg/kg L. candidum). Herbal-supplemented groups showed significantly improved (P ≤ 0.05) growth performance, feed utilization, and survival rates compared to the control, with T4 exhibiting the highest values. Significant enhancements of immune assays were observed in total hemocyte count, phagocytosis activity, total protein, glutathione peroxidase, and lysozyme activity in herbal-supplemented groups. Antioxidant indicators (catalase, superoxide dismutase, and phenoloxidase) were boosted while malondialdehyde levels decreased in herbal-treated shrimp. Following V. parahaemolyticus challenge, herbal diets effectively reduced cumulative mortality in L. vannamei. Histopathological examination revealed milder AHPND-associated alterations in A. herba-alba and L. candidum-treated groups, contrasting with atrophy, necrosis, and epithelial cell sloughing observed in the positive control. These findings demonstrate the immunostimulatory potential of A. herba-alba, L. japonica, and L. candidum as dietary supplements to enhance growth performance, immune function, and disease resistance in L. vannamei aquaculture, offering a promising strategy for sustainable shrimp farming.

Analysis of circRNA expression profile of Litopenaeus vannamei under pH and alkalinity interactive stress and verification of novel_circ_021024 and novel_circ_004981 regulating stress compounds metabolism

The global issue of salinization has made the use of saline-alkaline water in aquaculture increasingly vital. CircRNAs are a new type of endogenous non-coding RNA. Under high saline-alkaline stress, how circRNAs regulate the stress response of Litopenaeus vannamei, especially the mechanism of its immune and metabolic functions, is still unclear. This study aimed to analyze the expression profile of circRNAs and explore their response mechanisms in L. vannamei under the combined influence of high alkalinity and high pH. The results indicated that 127, 157, and 146 differentially expressed circRNAs (DECs) and 1401, 1547, and 1540 differentially expressed mRNAs (DEGs) were identified in the high-pH, alkalinity, and interaction groups, respectively. KEGG enrichment analysis revealed that DECs were mainly enriched in pathways such as sulfur metabolism, glycerophospholipids, and oxidative phosphorylation. The activities of antioxidant-related enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GSH - PX), increased, while the activities of energy - metabolism-related enzymes, like hexokinase (HK) and pyruvate kinase (PK), decreased. By combining weighted gene-related network analysis (WGCNA) with circRNA - mRNA data, it was found that the expression levels of essential genes related to metabolisms, such as novel_circ_007011, novel_circ_004981, and novel_circ_021024, declined. Gene-silencing experiments demonstrated that novel_circ_004981 and novel_circ_021024 could regulate the expression of glutathione peroxidase (GPx) and carbonic anhydrase - 3 (cah - 3) and further regulate the metabolic pathway and antioxidant system of L. vannamei. This study provides theoretical support for further understanding the stress-response mechanisms of circRNAs in L. vannamei under high-pH and alkalinity stress and offers a scientific basis for the development of saline-alkali aquaculture.

Host-Parasite Interactions and Integrated Management Strategies for Ecytonucleospora Hepatopenaei Infection in Shrimp

BACKGROUND

Ecytonucleospora hepatopenaei (EHP) is a major parasitic pathogen in shrimp causing hepatopancreatic microsporidiosis, which leads to significant growth retardation and global economic losses. This pathogen employs various immune evasion strategies that complicate treatment and management.

PURPOSE

This review examines the complex host-parasite interactions, focusing on the immune evasion mechanisms used by EHP. The study explores how EHP manipulates host immune pathways, including NF-κB, JAK/STAT, Toll, and IMD, to suppress immune responses, inhibit antimicrobial peptide production, and avoid detection, thus ensuring its persistence in the host.

METHODS

The authors reviewed recent research from databases like PubMed, Scopus, and Web of Science, including studies up to 2024. The keywords Ecytonucleospora hepatopenaei, immune evasion, EHP treatment, and associated words with topics were used in this search.

RESULTS

EHP induces oxidative stress, which weakens the host immune system while simultaneously upregulating antioxidant responses to favor its survival. The parasite also alters the gut microbiota and disrupts key cellular processes, such as cell cycle regulation, further enhancing its ability to sustain infection.

CONCLUSION

This review highlights the need for integrated management strategies, including disease-resistant breeding, microbiota modulation, and advanced diagnostics, to combat EHP. By providing an overview of EHP's immune evasion tactics, this study aims to advance knowledge in the field and support efforts to improve shrimp health and aquaculture sustainability.

Development of a colloidal gold immunochromatographic strip for the rapid on-site detection of Ecytonucleospora hepatopenaei (EHP)

The Pacific white shrimp (Penaeus vannamei), one of the world's most economically important aquatic species, is highly susceptible to Ecytonucleospora hepatopenaei (EHP), a pathogen that infects the hepatopancreas and causes hepatopancreatic microsporidiosis (HPM), leading to stunted growth and substantial economic losses in shrimp farming. Currently, no effective treatments for EHP exist, making rapid on-site detection and preventive measures essential for disease control. While nucleic acid-based detection methods are commonly employed, they require specialized equipment, controlled environments, and trained personnel, which increase costs. To address this limitation, we developed a colloidal gold immunochromatographic assay (GICA) strip for rapid on-site detection of EHP in shrimp farms. Using LC-MS/MS, 15 high-abundance EHP proteins were identified, with EhSWP3 ranked highest and selected as the optimal antigen detection target. Recombinant EhSWP3 was used to immunize mice, resulting in the development of monoclonal antibodies. The optimal capture and labeled antibody combination (1B6, 3A6) was identified and incorporated into the GICA strip. Testing with common shrimp pathogens and various microsporidia samples demonstrated the high specificity of the EHP test strip. The strip exhibited a sensitivity of 1.81 × 103 copies of the EHP-SSU rRNA gene for detecting EHP-infected shrimp and 1 × 104 purified EHP spores, indicating its strong sensitivity in practical applications. To facilitate on-site use, a simple GICA workflow was established using disposable pestles, Buffer A, and Buffer B, enabling detection within 15 min. Testing of 110 shrimp samples revealed a 90.0 % concordance between the GICA strip and qPCR results. This study marks the first development and application of an EHP antigen detection strip, offering a practical tool for rapid, on-site disease monitoring in shrimp farming.

SYNLAC prime probiotics enhances growth performance, and resistance of white shrimp, Penaeus vannamei to Enterocytozoon hepatopenaei and Vibrio alginollyticus: Insights into immune and metabolic pathway modulations

This study explores the impact of SYNLAC Prime probiotics on the growth performance, health status, and metabolic profile of white shrimp, Penaeus vannamei. Shrimp fed with the experimental diets, including the control diet without probiotic supplementation, and the diets supplemented with SYNLAC Prime probiotics at concentrations of 105 CFU (g diet)-1 (P5) and 106 CFU (g diet)-1 (P6) for 56 days. Results indicated a significant enhancement in growth performance in probiotic-treated shrimp relative to the control group, attributed to structural improvements in the digestive tract, particularly the increased abundances of B cells in the hepatopancreas. The administration of dietary probiotics markedly reduced the severity of Enterocytozoon hepatopenaei (EHP) infection and decreased cumulative mortalities following Vibrio alginolyticus challenge. Shrimp in the P6 group exhibited significant elevations in phenoloxidase activity, respiratory burst, lysozyme activity and phagocytic activity compared to control group. Furthermore, there was an upregulation of several immune-related genes in hepatopancreas, including serine protease (SP), prophenoloxidase (proPO) I, proPO II, and penaeidin 3a. Additionally, the expression of β-1, 3-glucan binding protein and SP mRNA was significantly increased in hemocytes. Untargeted metabolomics analysis using LC-MS/MS revealed significant changes in the hepatopancreas metabolic profile, highlighting alterations in energy metabolisms pathways, such as citrate cycle and nicotinate and nicotinamide metabolism, as well as amino acid metabolisms pathways including arginine and proline metabolism, taurine and hypotaurine metabolism, and histidine metabolism. These findings underscore the potential of SYNLAC Prime probiotics in enhancing shrimp growth, immune function, and metabolic pathways, offering valuable insights for advancing health management strategies in shrimp aquaculture.

Microsporidia secretory effectors and their roles in pathogenesis

Microsporidia, a group of unicellular eukaryotic parasites, rely intensely on secretory effectors for successful invasion and proliferation within host cells. This review focuses on the identification, characterization, and functional roles of effectors, including secretory proteins and microRNAs. The adhesion proteins like the Ricin-B-lectin facilitate initial invasion, which binds to the host cell surface. Once inside, microsporidia deploy a range of effectors to modulate host immune responses, such as serpin proteins, and redirect host cell metabolism to meet the parasite's nutritional needs through hexokinase. Some effectors such as microRNAs, alter the host gene expression to create a more favorable intracellular parasitic environment. In conclusion, the secretory effectors of microsporidia play a pivotal role spanning from host cell invasion to intracellular establishment. In the future, more effectors secreted by microsporidia will be studied, which will not only help to elucidate the molecular mechanism of pathogenic manipulation of the host but also help to provide the potential targets for anti-parasitic treatments.

Development of a Melting Curve-Based Triple Eva Green Real-Time PCR Assay for Simultaneous Detection of Three Shrimp Pathogens

Infections with Enterocytozoon hepatopenaei (EHP), infectious hypodermal and hematopoietic necrosis virus (IHHNV), and Decapod iridescent virus 1 (DIV1) pose significant challenges to the shrimp industry. Here, a melting curve-based triple real-time PCR assay based on the fluorescent dye Eva Green was established for the simultaneous detection of EHP, IHHNV, and DIV1. The assay showed high specificity, sensitivity, and reproducibility. A total of 190 clinical samples from Shandong, Jiangsu, Sichuan, Guangdong, and Hainan provinces in China were evaluated by the triple Eva Green real-time PCR assay. The positive rates of EHP, IHHNV, and DIV1 were 10.5%, 18.9%, and 44.2%, respectively. The samples were also evaluated by TaqMan qPCR assays for EHP, DIV1, and IHHNV, and the concordance rate was 100%. This illustrated that the newly developed triple Eva Green real-time PCR assay can provide an accurate method for the simultaneous detection of three shrimp pathogens.