Studies on the high occurrence of microsporidian parasite, Enterocytozoon hepatopenaei in cultured Pacific white shrimp, Litopenaeus vannamei (Boone, 1931) in West Bengal, East Coast of India

Abstract

Enterocytozoon hepatopenaei (EHP) is an emerging microsporidian pathogen in shrimp aquaculture. In the present study, prevalence rate of EHP in cultured Litopenaeus vennamei from West Bengal, east coast of India, was investigated. Histology of hepatopancreas of the infected animals showed eosinophilic to basophilic inclusions in the epithelial cells with moderate necrotic tubular detachment from the basal membrane. Extracted DNA from the hepatopancreatic tissues were subjected to PCR by using two different sets of primers targeting the ssu rRNA genes. An expected PCR product of 951 and 510 bp were yielded for the EHP-positive shrimp samples. Based on the BLASTP, the sequence of ssu rRNA gene (KU179095) of the collected samples showed 100% homology with EHP ssu rRNA gene sequences submitted in NCBI from different countries viz. Vietnam, Thailand, China and India. Further, all the field samples were found to be EHP+ by using a new second-generation primer targeting the spore wall protein gene (SWP) of EHP. For detection of EHP, 119 samples from East Midnapur district, 50 samples from North 24 Parganas district and 50 Samples from South 24 Parganas district were being screened. Overall prevalence rate of EHP in the cultured L. vennamei farm in West Bengal was estimated to be 84.9%, which was highest in comparison to earlier reports in India. Our finding showed that EHP could be detected from slow growing shrimps as well as in some cases from White Faeces Syndrome-affected animals. This is the first report on the occurrence of Enterocytozoon hepatopenaei in cultured L. vannamei in West Bengal, east coast of India.