Enterocytozoon hepatopenaei (EHP) is an emerging pathogen that affects P. vannamei shrimp in many SE Asian countries including Indonesia, Vietnam, China, Thailand, India and Malaysia. In the western hemisphere, EHP was reported for the first time in 2016 in farmed P. vannamei . Infected shrimp exhi bit reduced feeding and severely retarded growth. EHP is an enteric pathogen that replicates in the cytoplasm of tubule epithelial cells in the hepatopancreas. Anecdotal evidence suggest that EHP seems to be more prevalent in grow-out ponds where the salinity is high (>15 ppt) compared to grow-out ponds with low salinities (<5 ppt) . . Considering that Penae us vannamei shrimp is an euryhaline species which is now farmed worldwide in wide range of salinities, we were interested to determine if EHP is able to replicate in low salinities.
In this study, we describe d an experimental infection using fecal strings from known EHP-infected P. vannamei as a source inoculum. S pecific P athogen Free (SPF) P. vannamei shrimp were maintained at different salinities including 2 ppt, 15 ppt and 30 ppt and continuously challenged using fecal string over a period of three weeks . Infectivity of EHP containing fecal strings to animals reared at different salinities were confirmed by conventional PCR and histology . PCR data showed positive results in shrimp maintained at 2ppt, 15ppt and 30 ppt with higher prevalence at 2 ppt. H&E histology where animals reared at 2 ppt salinity displayed higher levels of infection compared to animals reared at 15 and 30 ppt, respectively. The results showed th at EHP can replicate well in shrimp maintained at low salinities.