The hepatopancreatic microsporidian infections we studied occurred
most frequently in MSGS P. monodon that were concomitantly
infected with several viruses (Chayaburakul et al., 2004) or
with pathogens in the lymphoid organ (Anantasomboon et al.,
2006) or hematopoietic tissue. They were less frequent in normal
shrimp. Thus, it is possible that the microsporidian infections were
opportunistic in nature, with the pathogen exploiting a weakened
immune status of the host. For example, the occurrence of human