Effects of Enterocytozoon hepatopenaei single-infection or co-infection with Vibrio parahaemolyticus on the hepatopancreas of Penaeus vannamei

Enterocytozoon hepatopenaei and Vibrio parahaemolyticus are the main pathogens affecting the Penaeus vannamei industry. To explore the effects of E. hepatopenaei single infection or co-infection with V. parahaemolyticus on the hepatopancreas of P. vannamei, hepatopancreas samples of shrimp naturally infected with the single pathogen or mixed pathogens were collected for histopathology and electron microscope observation. Transcriptome and gene expression quantitative analysis were obtained from different samples. The samples were divided into three groups: low concentration of E. hepatopenaei infection (A group), high concentration of E. hepatopenaei infection (C group), and high concentration of E. hepatopenaei co-infection with V. parahaemolyticus (B group). Histopathological results showed obvious tissue damage, hepatic tubule atrophy, and deformation in the high-concentration E. hepatopenaei infection group. In the co-infection group, deformation of hepatic tubules and vacuolation were observed in the cytoplasm. E. hepatopenaei 0.8–1.2 μm in length could be observed by electron microscopy. In pairwise comparisons of the transcriptome, 374 differentially expressed genes (DEGs) were obtained in the B vs C groups and 413 DEGs were obtained in the A vs C groups. In GO enrichment analysis, the immune system process (GO:0002376) was one of the top 10 biological processes in the B vs C groups, indicating that V. parahaemolyticus has a more significant effect on the shrimp's immunity. In KEGG pathway analysis, most of the DEGs in the A vs C group were annotated to lysosomes, biosynthesis of amino acids, and glycine, serine, and threonine metabolism. In the B vs C groups, DEGs were annotated mainly with pancreatic secretion, phagosomes, and the Rap1 signaling pathway. In addition, the glycolysis pathway was annotated by the significantly down-regulated genes in the A vs C groups.