Zoonotic Potential of Enterocytozoon bieneusi

Abstract

The reservoirs and the modes of transmission of the most frequent microsporidial species in humans, Enterocytozoon bieneusi, are still unknown. We have examined fecal samples of 26 humans and 350 animals from 37 species to find 18 samples containing this parasite from humans, cats, pigs, cattle, and a llama. Genotypic characterization of the internal transcribed spacer of the rRNA gene resulted in 14 different genotypes, 6 of them previously undescribed. Phylogenetic analysis revealed the lack of a transmission barrier between E. bieneusi from humans and animals (cats, pigs, and cattle). Thus, E. bieneusi appears to be a zoonotic pathogen.Microsporidia are newly emerging pathogens of humans and animals. Due to the small size of their spores and uncharacteristic staining properties they are difficult to detect by light microscopy. As a consequence, Enterocytozoon bieneusi, the species now known to be the most frequent in microsporidial infections of humans, was not discovered until 1985 (5). It is now recognized as a true pathogen, causing diarrhea especially in immunocompromised patients (2, 19).E. bieneusi has recently been found in the feces of animals, including pigs, rhesus macaques, cats, and cattle (4,11,13,18). However, the potential reservoirs and the mode of transmission of this pathogen are still unknown. Traditional epidemiological studies to address the zoonotic potential of this pathogen, for example, case control studies to identify risk factors such as contact with certain animals, are hampered by the small number of diagnosed microsporidial infections. Experimental infections of humans are prohibited for ethical reasons.As an alternative, this problem could be solved by a differentiation of strains within this species and a comparison of the strains found in humans with those detected in animals. Unfortunately, because the spores of E. bieneusi strains are morphologically indistinguishable and since this species cannot be cultured, traditional morphological, biochemical, and immunological methods are unavailable for strain differentiation. Instead, a genotypic method has been described to differentiate characteristic genotypes of the internal transcribed spacer (ITS) of the rRNA gene (rDNA) (16).Before this report, 14 ITS genotypes were known from humans (5 genotypes), pigs (6 genotypes), a cat (1 genotype), and cattle (2 genotypes) (1, 13, 15-18), but since no identical ITS genotypes of E. bieneusi were found in humans and animals its zoonotic potential was controversially discussed. In this report we investigated diarrheal fecal samples of another 26 humans and 350 animals from 37 species. Molecular epidemiological analysis of these data now offers convincing evidence for a zoonotic potential of E. bieneusi. MATERIALS AND METHODSOrigin of stool and fecal samples. Fecal samples from 34 primates (26 humans, one chimpanzee, four gorillas, two baboons, and one mandrill), 122 carnivores (one mustelid, one polar bear, 60 cats, and 60 dogs), 147 even-toed ungulates (one wild boar, 50 domestic pigs, fo...

Enterocytozoon bieneusiin human and animals, focus on laboratory identification and molecular epidemiology

“…The two exceptions were genotypes isolated in HIV-positive human in Thailand (Leelayoova et al, 2006). Finally only one genotype named O was found both in HIV-positive patients in Thailand and in swine in Germany (Dengjel et al, 2001;leelayoova et al, 2006). The subgroup 1f, 1g and 1h contained very few genotypes, 2, 1 and 1 respectively, isolated from very few studies (Breitenmoser et al, 1999;Breton et al, 2007;Cama et al, 2007;Dengjel et al, 2001;Espern et al, 2007;Jeong et al, 2007;Liguory et al, 2001;Liguory et al, 1998).…”

“…Group 3 is composed of three genotypes isolated from muskrat in USA and one isolated from a cat in Portugal (Lobo et al, 2006a;Sulaiman et al, 2003b). Group 2 consisted of genotypes isolated in farm animals, almost exclusively from cattle (10 genotypes), with one genotype also found in chicken (Dengjel et al, 2001;Fayer et al, 2007;Lee, 2007;Lobo et al, 2006a;Reetz et al, 2002;Rinder et al, 2000;Santin et al, 2005;Sulaiman et al, 2004). Interestingly genotypes from cattle were found in very different countries and continents (Germany, Portugal, USA and Korea).…”

“…To date WL11 was found in HIVpositive patients in Peru only, and in fox and cat, in USA and Columbia respectively Sulaiman et al, 2003aSulaiman et al, , 2003b. Genotype K is most largely widespread since it was isolated in human in Europe, South America and Africa and in domestic animals (cat, and cattle) in the same continents (Breton et al, 2007;Dengjel et al, 2001;Espern et al, 2007;Liguory et al, 2001;Liguory et al, 1998;Lobo et al, 2006a;Sadler et al, 2002;Santin et al, 2006;Sarfati et al, 2006;Sulaiman et al, 2003aSulaiman et al, , 2003bTumwine et al, 2002). It is to be noted that, on the contrary to types A and B, type K may be common in developing countries but rare in Europe (Liguory et al, 2001;Sadler et al, 2002).…”

“…In subgroup 1e, all genotypes but two (n = 14) were isolated from animals. The animals involved were swine with ten genotypes isolated in Switzerland, Germany, Korea and Thailand and cattle with three genotypes from Germany and Korea (Breitenmoser et al, 1999;Buckholt et al, 2002;Dengjel et al, 2001;Jeong et al, 2007;Lee, 2007;Rinder et al, 2000). The two exceptions were genotypes isolated in HIV-positive human in Thailand (Leelayoova et al, 2006).…”

“…The development of new tools for diagnosis and especially molecular methods have shown that E. bieneusi was present in a large number of domestic and wild mammals as well as birds (Haro et al, 2006;Haro et al, 2005;Kondova et al, 1998;and reviewed in Mathis et al, 2005). Thanks to molecular methods again, the potential of zoonotic transmission was quickly supported by phylogenetic studies showing that several genotypes can infect humans as well as animals (Curry, 1999;Dengjel et al, 2001;Drosten et al, 2005;Lobo et al, 2006a;Santin et al, 2006;Sulaiman et al, 2003a;Sulaiman et al, 2003b;Sulaiman et al, 2004). The focus of this revue is to present and discuss the more recent advances on diagnosis and zoonotic potential of Enterocytozoon bieneusi infections.…”