Phylogenetic Approach to the Variability of the Microsporidian Enterocytozoon bieneusi and Its Implications for Inter- and Intrahost Transmission

Abstract

Enterocytozoon bieneusi is a microsporidian parasite that infects many vertebrate animals, including humans. The rDNA internal transcribed spacer (ITS) shows a hypervariable sequence; however, so far no clear information has been inferred about strain evolution in this species. We reviewed all the sequences described and performed a phylogenetic study. Four groups of sequences strongly differentiated from each other were detected, although most of the isolates (94%) corresponded to group I. The highly diverse sequences of this group were analyzed using median-joining networks. The host species (humans, pets, swine, cattle, birds, and wild animals) and the continents of origin of the isolates were considered. Central haplotypes in the network were obtained from very diverse hosts and geographical origins. The results show that although E. bieneusi has a broad host specificity, transmission is not completely free: some strains were able to circulate within a given host species and were only occasionally transmitted to another host. Additionally, while not relevant for swine or cattle hosts, geography seems to be a relevant factor for human infection by E. bieneusi.

First Cases of Microsporidiosis in Transplant Recipients in Spain and Review of the Literature

“…In reference to the genetic variation among isolates of E. bieneusi (18,47), analyses of ribosomal DNA internal transcribed spacer (ITS) sequences have identified more than 70 genotypes of E. bieneusi (18,47). Some of these genotypes have been recognized as host specific, while others have been found to infect humans and animals, supporting the likelihood of zoonotic transmission (18,47). In our 2 patients, genotype D was identified.…”

“…Patient 1 was positive for CMV antigen in colonic mucosa, which is a common finding, since CMV infection is one of the major infectious complications in transplant recipients with nonsystemic symptoms that include fever, diarrhea, myalgias, malaise, and, in severe cases, hepatitis, pneumonia, and colitis (18). However, the gastrointestinal tract is one of the least common sites of CMV disease.…”

“…In three of five E. cuniculi infections described to occur in SOT and BMT recipients, the genotype was investigated; two of these infections showed ITSrelated genotype III, known as the "dog strain" (30), and for the third infection, a new genotype, genotype IV, was recently described (44). In reference to the genetic variation among isolates of E. bieneusi (18,47), analyses of ribosomal DNA internal transcribed spacer (ITS) sequences have identified more than 70 genotypes of E. bieneusi (18,47). Some of these genotypes have been recognized as host specific, while others have been found to infect humans and animals, supporting the likelihood of zoonotic transmission (18,47).…”

Molecular Epidemiologic Characterization of Enterocytozoon bieneusi in HIV-Infected Persons in Benin City, Nigeria

“…Phylogenetically, most of the study participants were infected with genotypes belonging to the initially described human pathogenic group 10 or the recently renamed Group 1 ( Figure 1). 1,12 All six known genotypes and two new genotypes belonged to this group. The latter had one nucleotide difference (G to A substitution) from genotype A or two nucleotide differences (T to C and G to A) from genotype IV, and they were named as Nig1 and Nig2, respectively.…”

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“…Among over 100 E. bieneusi ITS genotypes identified in humans and animals thus far, several unique groups (Groups II-V) of genotypes are found in specific groups of animals, thus have less public health importance. Nevertheless, a large group (Group I) of ITS genotypes have been found in both humans and animals [16,17]. These observations need to be substantiated by sequence characterization of other genetic markers [18].…”