Host Specificity of Enterocytozoon bieneusi and Public Health Implications

High genetic diversity for E. bieneusi has been revealed using genetic polymorphisms at the ITS locus with almost 500 genotypes identified in humans, livestock, companion animals, wild mammals, birds, and water worldwide. E. bieneusi genotypes vary in genetic or hereditary traits and 11 phylogenetic groups have been recognized using ITS genotyping data. Genotypes in Group 1 and Group 2 have been found in a broad range of hosts including humans and are probably responsible for most zoonotic or cross-species E. bieneusi infections, whereas host adaptation seems to be more common in genotypes of Groups 3 to 11. MLST and population genetic data have provided important insights into the host adaptation mechanism for some genotypes, but additional MLST tools and genomic data are required to elaborate the host specificity of E. bieneusi and its public health implications. Enterocytozoon bieneusi is the most common cause of human microsporidiosis and it also infects a wide range of mammals and birds worldwide. The role of animals in the transmission of this parasite to humans and its public health importance remain poorly elucidated. This review summarizes all E. bieneusi genotypes identified thus far based on sequence analysis of the ribosomal internal transcribed spacer (ITS) from specimens obtained from humans, domestic and wild animals, and water sources; it examines genotypes, host and geographical distribution, analyzes inter- and intragenotype group host specificity, and interprets the public health significance of genotype groups and major zoonotic genotypes, with the goal of improving our understanding of host specificity in E. bieneusi and its implications for interspecies and zoonotic transmission. Enterocytozoon bieneusi is the most common cause of human microsporidiosis and it also infects a wide range of mammals and birds worldwide. The role of animals in the transmission of this parasite to humans and its public health importance remain poorly elucidated. This review summarizes all E. bieneusi genotypes identified thus far based on sequence analysis of the ribosomal internal transcribed spacer (ITS) from specimens obtained from humans, domestic and wild animals, and water sources; it examines genotypes, host and geographical distribution, analyzes inter- and intragenotype group host specificity, and interprets the public health significance of genotype groups and major zoonotic genotypes, with the goal of improving our understanding of host specificity in E. bieneusi and its implications for interspecies and zoonotic transmission. a population of organisms with a common origin characterized by strong linkage disequilibrium among genetic loci with little or no genetic divergence among isolates in a host at any given time. a population characterized by relatively frequent recombination in which a clone emerges and becomes the predominant one for an extended period. the ability of a pathogen to circulate and cause disease in a host population. It is an indicator of the pathogen’s fitness levels or the ability to adapt to its host environment, but might result in reduction in transmission of this pathogen to other hosts. a typing approach based on hypermutation of the ribosomal ITS of an organism, and is used to discriminate among isolates from various sources. typically refers to the systematic sequencing of five to seven well-conserved, housekeeping loci with genetic polymorphisms within the genome of an organism. Different nucleotide sequences at a single locus represent distinct alleles, which define the allelic profile or sequence type of an isolate when the alleles of all loci are considered. a subdivision of genetics, and a part of evolutionary biology, that studies genetic variation within and between populations and adaptation of organisms to host environments.