Occurrence of Enterocytozoon hepatopenaei (EHP) infection on Penaeus vannamei in one rearing cycle

The microsporidian parasite Enterocytozoon hepatopenaei (EHP) is an emerging problem in the marine shrimp industry, primarily in Asian countries such as China, Thailand, India, Malaysia, Indonesia, and Vietnam. A screening was conducted to investigate the prevalence of EHP after a fixed period of culturing for 1 rearing cycle in 3 states of Malaysia. The screening stages covered Penaeus vannamei post larvae (PL) and after 14-30, 31-50, 51-70, and 71-90 d of culture in 1 production cycle. A total of 279 samples were amplified using a PCR assay targeting the gene encoding a spore wall protein (SWP) of EHP. The EHP infection was initially detected in the hatchery and increased to 96.6% after the shrimp were transferred to the pond. The positive EHP sequence showed 91 to 100% similarity to sequences from India, Thailand, Vietnam, Indonesia, and Latin America. EHP infection increased throughout 1 rearing cycle due to factors such as the cannibalistic feeding habits of shrimp and the presence of unknown vectors or carriers of EHP in the culture ponds. Hence, the finding from the current study will be fundamental for other studies concerning EHP.