Experimental Infection of Enterocytozoon hepatopenaei (EHP) by Water and Sediment Transfer Between Pacific White Shrimp (Penaeus vannamei) and Green Mud Crab (Scylla paramamosain)

Enterocytozoon hepatopenaei (EHP) is an important shrimp pathogen, causing growth retardation syndrome which leads to substantial economic losses worldwide. In this study, we examined the possibility of EHP transmission between Pacific white shrimp (Penaeus vannamei) and green mud crabs (Scylla paramamosain), a common benthic species in shrimp culture environments. Naturally infected shrimp (with EHP loads ranging from 10² to 10⁶ copies/µL) were used as donors for EHP transmission to EHP-free crabs and shrimp through water and sediment transfer. The recipient shrimp became EHP-positive 7 days post-exposure (dpe) (with EHP loads ranging from 10¹ to 10⁴ copies/µL). Histopathological examination confirmed EHP spores in the hepatopancreatic cells of the recipient shrimp at 7 and 14 dpe. The recipient crabs were EHP-positive after 14 dpe (EHP loads between 10¹ and 10² copies/µL) and the crabs could transmit EHP back to the recipient shrimp (EHP loads ranging from 10¹ to 10² copies/µL) 14 dpe via the same route. Although the crabs tested positive for EHP through PCR and qPCR, no histopathological change was observed. The present study suggests that green mud crabs may act as a mechanical vector for EHP transmission, providing information to enhance biosecurity protocols in shrimp farms to reduce the risk of EHP contamination.