Types of cells in the hepatopancreas of the Pacific whiteleg shrimp Litopenaeus vannamei being infected by Enterocytozoon hepatopenaei

Abstract

Enterocytozoon hepatopenaei (EHP), the fungus-related micro-organism that infects the hepatopancreas of marine shrimp, is believed to cause growth retardation of the infected shrimp. As the hepatopancreatic cells are composed of different cell types that support the digestive system and innate defense, malfunction of the infected cells could lead to growth retardation and weakness. This study aimed to determine of the percentage of each hepatopancreatic cell type infected by EHP and its infectious levels in the normal and growth-retarded Pacific whiteleg shrimp Litopenaeus vannamei. Histological examination revealed that all the cell types examined were infected with EHP, with significantly higher (p<0.01) percentage on the M- and Fcells, compared to other cell types. The R-, B- and F-cells of the growth-retarded shrimp were infected at significantly lower (p<0.05) percentage than the same cell types of the normal shrimp. By PCR, positive reactions of EHP infection were detected in all shrimp samples, both in the normal and growth-retarded shrimp, but only at the nested PCR level. Also, the relative density of the EHP load in the hepatopancreas of the two shrimp groups did not differ statistically. These results suggest that growth retardation in L. vannamei currently exists may not be due to EHP infection.

Keywords

• growth retardation
• white-feces disease
• shrimp culture
• enterocytozoon hepatopenaei
• microsporidia