Tissue and cell types infected by Ecytonucleospora hepatopenaei (EHP)

Area of Science:

• Aquaculture Pathology
• Marine Biology
• Invertebrate Zoology

Background:

• Ecytonucleospora hepatopenaei (EHP) is a significant microsporidian pathogen impacting shrimp aquaculture globally.
• The hepatopancreas is the primary known target, but EHP's full tissue and cell tropism, especially in severe infections, is not fully understood.
• Understanding EHP tropism is crucial for disease management in shrimp farming.

Purpose of the Study:

• To comprehensively investigate the histopathology of EHP infections in severely infected Penaeus vannamei.
• To determine the precise tissue and cell tropism of EHP within the shrimp host.
• To assess the potential for EHP to cause systemic infections.

Main Methods:

• Histopathological examination of tissues from heavily infected Penaeus vannamei.
• Ultrastructural pathology to analyze cellular infection.
• Correlation of infection severity with observed lesions in the hepatopancreas.

Main Results:

• EHP spores were found within the digestive system but not in non-digestive tissues (gills, heart, gonads, etc.).
• Infection was restricted to epithelial cells of the hepatopancreas, midgut, and midgut caeca, areas lacking chitin.
• Specific hepatopancreas cell types (R, F, B, E, M cells) were identified as infected.
• Epithelial cells of the esophagus, stomach, and hindgut remained unaffected despite spore presence, due to chitinous layers.

Conclusions:

• EHP exhibits strict cell tropism, exclusively infecting specific epithelial cells of the shrimp digestive system.
• EHP does not cause systemic infections in Penaeus vannamei, even under severe disease conditions.
• The presence of chitinous layers in certain digestive tract sections prevents EHP infection.