Fig 1. Phylogeny and host range of known members of the EGM.

Except for E. bieneusi infecting humans, terrestrial mammals, and birds, all other members of the EGM infect aquatic hosts. Erection of the genus Enterocytozoon coincided with emergence of its type species E. bieneusi during the HIV/AIDS pandemic in the 1980s. Subsequent description of proposed cogeneric EGM genera (Nucleospora, Paranucleospora/Desmozoon, Enterospora, Hepatospora, Obruspora) and closely related genera (e.g., Enterocytospora and Parahepatospora) have occurred over the past 3 decades. In most cases, emergence has been reported in domesticated terrestrial and aquatic food animals. However, certain EGM and related taxa have also been described infecting wild-animal hosts (e.g., foxes, primates, crabs), some of which reside in invasive populations outside of their native ranges. In at least one case (Paranucleospora/Desmozoon), the parasite is known to cycle between an invertebrate (copepod crustacean) and fish (salmon) host, raising the prospect of the capacity for trophic transfer in other members of the EGM. The Bayesian phylogenetic analysis was conducted using MrBayes version 3.2.5 [27]. The evolutionary model applied included a GTR substitution matrix, a four-category autocorrelated gamma correction, and the covarion model for 4 million generations, 1 million of which were discarded as burn-in. EGM, Enterocytozoon group Microsporidia; GTR, generalized time reversible.