Evidence of Ecytonucleospora hepatopenaei in environmental reservoirs and macrofaunal carriers from shrimp aquaculture ecosystems of south West India.

Abstract

Ecytonucleospora hepatopenaei (EHP) is an emerging microsporidian parasite that causes growth retardation and reduced production in shrimp aquaculture. Transmission is considered to occur mainly through horizontal pathways, including ingestion of spores released by infected shrimp or exposure to contaminated environmental material. However, data on occurrence of EHP DNA in environmental matrices and potential macrofaunal carriers along the Karnataka coast are limited. This study assessed the presence of EHP DNA in water, sediment, seaweeds, and mollusks from shrimp farms and surrounding aquatic environments. Among the 124 samples screened by species-specific PCR, EHP DNA was detected in 78 (62.9%) across all sample types. These results support the presence of EHP-associated DNA in both macrofauna and environmental matrices in aquaculture environments, but the limited sample sizes preclude strong conclusions about relative detection rates or the strength of any association between EHP DNA and sample types. Phylogenetic analysis of SSU rRNA sequences showed close clustering with previously reported Indian EHP isolates. Calcofluor white and Giemsa-stained sediment samples revealed putative microsporidian spore-like structures. These findings demonstrate widespread detection of EHP -associated DNA in environmental matrices and selected macrofauna. The results underscore the need for comprehensive management in shrimp farming, including regular monitoring, strict biosecurity, and monitoring of wild macrofauna and other potential environmental sources. Such measures are essential to mitigate EHP impact and support sustainable, profitable aquaculture on India's west coast.