Synergistic pathogenic mechanisms of EHP and IHHNV co-infection in Litopenaeus vannamei: Insights from RNA-seq analysis.

Ecytonucleospora (=Enterocytozoon) hepatopenaei (EHP) is an intracellular parasitic microsporidian, Infectious hypodermal and haematopoietic necrosis virus (IHHNV) is a linear single-stranded DNA virus. Both of them are widespread pathogens in shrimp farming, causing slow growth in shrimp and leading to significant economic losses. Litopenaeus vannamei (L. vannamei), the dominant species in shrimp farming, can be co-infected by EHP and IHHNV. According to our prior research, EHP and IHHNV exhibit synergistic interactions during infection. However, the underlying mechanisms of their co-infection remain unclear. In this study, L. vannamei from four experimental groups (EHP infected group, IHHNV infected group, EHP and IHHNV co-infected group, healthy group) were compared by transcriptome sequencing to analyze the synergistic pathogenic mechanisms of IHHNV and EHP. The results showed that co-infection induced more pronounced changes in the expression of genes related to metabolism, growth, and immunity compared to single infections. Specifically, EHP infection had a greater impact on shrimp physiology and immune responses, suggesting a dominant role in co-infection. Meanwhile, IHHNV infection disrupted metabolic processes, inhibited molting, and exacerbated the immune suppression caused by EHP. The synergistic pathogenic mechanism of IHHNV and EHP may involve EHP weakening the immune defenses of L. vannamei, facilitating IHHNV infection and proliferation. Additionally, the metabolic dysregulation induced by IHHNV may further enhance consumption of cellular nutrients and energy by EHP. These findings preliminarily reveal the synergistic pathogenic mechanism of EHP and IHHNV in L. vannamei, offering a theoretical foundation for understanding disease outbreaks in shrimp farming and guiding strategies against multi-pathogen infections.