Enterocytozoon hepatopenaei (EHP) is a microsporidian parasite that was first characterized and named from the giant or black tiger shrimp Penaeus monodon from Thailand in 2009 (Tourtip et al. 2009. J. Invertebr. Pathol. 102: 21-29). It was discovered in slow-growing shrimp but was not statistically associated with slow growth at that time. EHP is confined to the shrimp hepatopancreas (HP) and morphologically resembles an unnamed microsporidian previously reported in the HP of Penaeus japonicas from Australia in 2001. Together, these studies suggest that EHP is not an exotic pathogen but that it is endemic to Australasia. Later, it was found that EHP could also infect exotic Penaeus vannamei imported for cultivation in Asia and that it could be transmitted directly from shrimp to shrimp by the oral route (Tangprasittipap et al. 2013. BMC Vet Res. 9:139). This differed from the most common microsporidian previously reported from cotton shrimp, where transmission required an intermediate fish host, allowing disruption of transmission by the exclusion of fish from the production system.