Regional Prevalence and Molecular Detection of Enterocytozoon hepatopenaei in Coastal Shellfish from Korea

TL;DR

This study found that shellfish near shrimp farms in Korea can carry a microsporidium that affects shrimp, suggesting the need for monitoring to prevent its spread.

Contribution

The study demonstrates that bivalves can mechanically carry and transmit Enterocytozoon hepatopenaei spores in aquaculture environments.

Findings

EHP DNA was detected in gill and digestive tissues of oysters, scallops, mussels, and clams.

Histopathology confirmed spore invasion in clams' intestinal epithelium within 24 hours.

Bivalves may act as mechanical carriers of EHP between shrimp farms and coastal waters.

Abstract

We detected Enterocytozoon hepatopenaei (EHP) from several farmed bivalves near shrimp ponds in Korea. EHP invaded the intestinal epithelium of clams within 24 h. Bivalves may serve as mechanical carriers with transmission potential for EHP between shrimp ponds and adjacent coastal waters. Regular monitoring of coastal shellfish is therefore recommended for early detection and preventing the spread of EHP in aquaculture.

EHP causes hepatopancreatic microsporidiosis in shrimp, leading to growth retardation without notable mortality. To examine potential environmental carriers, farmed bivalves were collected near shrimp ponds in Korea and screened for EHP using nested PCR targeting the spore-wall-protein gene. DNA of EHP was mainly detected in gill and digestive tissues of oysters, scallops, mussels, and clams. Histopathology after 24 h immersion exposure confirmed spores within the intestinal epithelium of clams, indicating short-term invasion potential. These results suggest that bivalves can retain and mechanically transfer EHP spores through shared seawater between shrimp farms and surrounding areas. Considering the environmental persistence of EHP, continuous surveillance of local invertebrates is recommended to reduce the risk of EHP introduction and further spread in aquaculture systems.

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