Host specificity in Enterocytozoon bieneusi and public health implications

Authors: LI, WEI - Northeast Agricultural University; Santin-Duran, Monica; FENG, YAOYU - China Agricultural University

Submitted to: Trends in Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2019
Publication Date: 5/7/2019
Citation: Li, W., Santin, M., Feng, Y. 2019. Host specificity in Enterocytozoon bieneusi and public health implications. Trends in Parasitology. 35(6):436-451. https://doi.org/10.1016/j.pt.2019.04.004.
DOI: https://doi.org/10.1016/j.pt.2019.04.004

Interpretive Summary: Microsporidia are microscopic parasites that infect all major animal groups from invertebrates to fish to birds and mammals, including domesticated animals and humans. Enterocytozoon bieneusi is the most frequently diagnosed species of Microsporidia in humans worldwide, mainly associated with chronic diarrhea and wasting syndrome. The role of animals in the transmission of this parasite to humans and the public health importance remain poorly elucidated. Within the species E. bieneusi considerable genetic diversity has been found. Based on differences in nucleotide sequence of the ITS region of the ribosomal DNA over 500 genetically distinct types (genotypes) of E. bieneusi have been identified from specimens isolated from feces of infected humans and animals. Some E. bieneusi genotypes appear to have a narrow host range and others appear potentially zoonotic with the ability to infect many animals including humans. Information presented in this review includes a summary all the E. bieneusi ITS genotypes identified thus far from humans, animals, and water sources, examines their host and geographical distribution, and interprets the public health significance of various genotypes with the goal of improving our knowledge of host specificity in E. bieneusi and its implications to zoonotic transmission. This information is intended for use by public health specialists worldwide at local to national and global levels for purposes from laboratory identification to environmental and public health policy formulation.

Technical Abstract: Among ~1,500 microsporidian species with considerable variations in biology, genetics, genomics, and host specificity, Enterocytozoon bieneusi is the most common cause of human microsporidiosis and infects a surprising variety of other mammals and birds worldwide. The role of animals in the transmission of microsporidiosis to humans and the public health importance of the zoonotic pathogen remain poorly elucidated. Genotyping of E. bieneusi isolates based on the nucleotide sequence polymorphism of the ribosomal internal transcribed spacer (ITS) has identified near 500 genotypes in humans, livestock, companion animals, wild mammals, birds, and water. These E. bieneusi genotypes vary in hereditary traits and form several genetic groups in phylogenetic analysis of the ITS sequences. Most ITS genotype groups (Groups 3 to 11) have shown strong host adaptation and thus have limited zoonotic importance. In contrast, most of the ITS genotypes in Group 1 affect a broad range of hosts and are probably responsible for most cross-species E. bieneusi infections. Nevertheless, host adaptation was also seen in some of Group 1 isolates by host range analysis, multilocus sequence typing (MLST), and population genetic analysis of E. bieneusi. Host adaptation appears to be also common among Group 2 E. bieneusi genotypes, with different genotypes preferentially infecting bovines and ovines. The present review summarizes all the E. bieneusi ITS genotypes identified thus far from humans, animals, and water sources, examines their host and geographical distribution, analyzes inter- and intra-group host specificity at the ITS and MLST levels, and interprets the public health significance of various ITS genotype groups, subgroups within Group 1, and major zoonotic genotypes, with the goal of improving our knowledge of host specificity in E. bieneusi and its implications to interspecies and zoonotic transmission of this important pathogen.