The Effect Of Salinity On Enterocytozoon hepatopenaei Infection in Penaeus vannamei Under Experimental Conditions

Abstract

Background: Enterocytozoon hepatopenaei (EHP) is an enteric pathogen that affects Penaeus vannamei and Penaeus monodon shrimp in many SE Asian countries. In the western hemisphere, EHP was reported for the first time in 2016 in farmed P. vannamei in Venezuela. Anecdotal evidence suggests that EHP is more prevalent in grow-out ponds where the salinity is high (>15 parts per thousand (ppt)) compared to grow-out ponds with low salinities (<5 ppt). Considering that P. vannamei is an euryhaline species, we were interested in knowing if EHP can propagate in P. vannamei in low salinities. Results: In this study, we described an experimental infection using fecal strings as a source inoculum. Specific Pathogen Free (SPF) P. vannamei were maintained at three different salinities (2 ppt, 15 ppt, and 30 ppt) while continuously challenged using feces from known EHP-infected P. vannamei over a period of three weeks. The fecal strings, used as a source of EHP inocula in the challenges, was sufficient to elicit an infection in shrimp maintained at the three salinities. The infectivity of EHP in shrimp reared at 2 ppt, 15 ppt, and 30 ppt salinities was confirmed by PCR and histopathology. The prevalence and the severity of the EHP infection was higher at 30 ppt than at 2 ppt and 15 ppt. Conclusion: The data suggests that fecal strings are a reliable source of EHP inoculum to conduct experimental challenges via the fecal-oral route. An EHP infection can occur at a salinity as low as 2 ppt, however, the prevalence and the severity of the EHP infection is higher at a salinity of 30 ppt.

Factors affecting water quality and shrimp production in the mixed mangrove‐shrimp systems in the Mekong Delta of Vietnam

“…monodon ranged from 1 to 57‰, and the most suitable salinity range is 10–35‰ (Ye et al, 2009). The high fluctuated and high concentration of salinity in pond water could affect the immune system of shrimp and make them highly vulnerable to pathogens (Aranguren Caro et al, 2021; Nikapitiya et al, 2014). Therefore, the shrimp producers should consider salinity condition in the pond water when they recruitment and add the new shrimp seeds.…”