Experimental infection of Enterocytozoon hepatopanaei parasite (EHP) of penaeid shrimp in Indian marine crabs.

Enterocytozoon hepatopanaei parasite (EHP) is identified as an emerging pathogenic microsporidium parasite in shrimp culture industry. Though the etiology, disease pattern and sustainability of shrimp are well known, significantly less research has been carried out about the disease transmission and symptoms of infected aquatic animals. The present study aims is to determine the disease carrier status of five different species of Indian marine crabs (Scylla olivacea, Scylla serrata, Portunus pelagicus, Ocypode quadrata and Portunus sanquinolentus) using EHP. At the first instance, oral infection and intramuscular injection were performed to determine the susceptibility of the parasite at 50 days post-infection and it was observed that there was no mortality. The experimental infected crabs were confirmed by polymerase chain reaction, bioassay and histopathology. The crabs were EHP-PCR positive at 5th day post-infection (d.p.i) in gills, heart, hepatopancreas, haemolymph and muscle tissue. However, after 5th d.p.i EHP was PCR negative in all the tissue samples. There were no mortalities and histological changes in the negative group and experimental group. Therefore, marine crabs are found to be not suitable hosts for replicating EHP spores but crabs fecal matters are PCR positive till 5th d.p.i. Therefore, marine crabs are having the possibilities of acceptance as a vector for Enterocytozoon hepatopanaei in shrimp. Shrimp farmers need to take necessary action to control this deadly infection in shrimp ponds.