Detection of the microsporidian Enterocytozoon hepatopenaei (EHP) and Taura syndrome virus in Penaeus vannamei cultured in Venezuela

The microsporidian Enterocytozoon hepatopenaei (EHP) is an intracellular parasite that has become a critical threat to the shrimp farming industry in SE Asia. This parasite replicates in the hepatopancreas and midgut, and infected shrimp exhibit reduced feeding and severely retarded growth. In this study, we describe the first case of EHP-infected Penaeus vannamei cultured in Venezuela. Its histopathology is very similar to that of SE Asia EHP, with infected shrimp showing basophilic inclusions in hepatopancreas. Upon in situ hybridization of an EHP 18S rRNA gene fragment labeled with digoxigenin, the probe reacted intensely to the basophilic inclusions within the cytoplasm of the infected cells. We also compared the nucleotide sequence similarities in 18S rRNA gene (1095-bp), in β-tubulin (583-bp) and spore wall protein (431-bp) genes between the Venezuela EHP and SE Asia isolates; and the results showed 99%, 93% and 91% identities, respectively. This suggests that the Venezuela EHP was not recently introduced from SE Asia. In a shrimp farm that was affected by EHP, Taura syndrome virus (TSV) was also detected in the P. vannamei by RT-qPCR and histological examinations. TSV is a major pathogen in penaeid shrimp aquaculture and has caused substantial economic losses during the last 2 decades, however, TSV has not been reported since 2011. This TSV was determined to be a Venezuela genotype based on the phylogenetic analysis in the capsid protein 2 gene and it showed to have sequence identities of 97% (nucleotide) and 98% (amino acid) to a Venezuela isolate found in 2005. The emergence of EHP and occurrence of TSV in the Venezuela will have a significant impact on the shrimp production if they spread to other farms. Therefore, the shrimp cultured within the country should be monitored closely for the presence of EHP and TSV.