Resistance of Nosema ceranae to different exposure conditions has been evaluated by using Sytox green and DAPI (4′,6-diamidino-2-phenylindole) to test spore viability. High thermotolerance at 60 and 35°C and resistance to desiccation were observed. However, a significant decrease in viability after freezing and a rapid degeneration of spores maintained at 4°C were also detected.

Microsporidia are ubiquitous opportunistic parasites in nature infecting all animal phyla, and the zoonotic potential of this parasitosis is under discussion. Fecal samples from 124 pigeons from seven parks of Murcia (Spain) were analyzed. Thirty-six of them (29.0%) showed structures compatible with microsporidia spores by staining methods. The DNA isolated from 26 fecal samples (20.9%) of microsporidia-positive pigeons was amplified with specific primers for the four most frequent human microsporidia. Twelve pigeons were positive for onlyEnterocytozoon bieneusi(9.7%), 5 forEncephalitozoon intestinalis(4%), and one forEncephalitozoon hellem(0.8%). Coinfections were detected in eight additional pigeons:E. bieneusiandE. hellemwere detected in six animals (4.8%);E. bieneusiwas associated withE. intestinalisin one case (0.8%); andE. hellemandE. intestinaliscoexisted in one pigeon. No positive samples forEncephalitozoon cuniculiwere detected. The internally transcribed spacer genotype could be completed for oneE. hellem-positive pigeon; the result was identical to the genotype A1 previously characterized in anE. hellemSpanish strain of human origin. To our knowledge, this is the first time that human-related microsporidia have been identified in urban park pigeons. Moreover, we can conclude that there is no barrier to microsporidia transmission between park pigeons and humans forE. intestinalisandE. hellem. This study is of environmental and sanitary interest, because children and elderly people constitute the main visitors of parks and they are populations at risk for microsporidiosis. It should also contribute to the better design of appropriate prophylactic measures for populations at risk for opportunistic infections.

Microsporidia are currently considered emerging pathogens responsible for life-threatening infections in organ transplant recipients. Here, we describe the first cases of intestinal microsporidiosis by Enterocytozoon bieneusi genotype D in two non-HIV-infected renal transplant recipients from Spain. Previously reported cases of microsporidiosis in organ transplant recipients have also been reviewed, highlighting the necessity of considering organ transplant recipients a risk group for microsporidiosis. A systematic search for these parasites is recommended in cases of persistent diarrhea and in the differential diagnosis of other syndromes, such as chronic fever of unknown etiology.

Recent studies suggest the involvement of water in the epidemiology of Cyclospora cayetanensis and some microsporidia. A total of 223 samples from four drinking water treatment plants (DWTPs), seven wastewater treatment plants (WWTPs), and six locations of influence (LI) on four river basins from Madrid, Spain, were analyzed from spring 2008 to winter 2009. Microsporidia were detected in 49% of samples (109/223), Cyclospora spp. were detected in 9% (20/223), and both parasites were found in 5.4% (12/223) of samples. Human-pathogenic microsporidia were detected, including Enterocytozoon bieneusi (C, D, and D-like genotypes), Encephalitozoon intestinalis , Encephalitozoon cuniculi (genotypes I and III), and Anncaliia algerae . C. cayetanensis was identified in 17 of 20 samples. To our knowledge, this is the first study that shows a year-long longitudinal study of C. cayetanensis in drinking water treatment plants. Additionally, data about the presence and molecular characterization of the human-pathogenic microsporidia in drinking water, wastewater, and locations of influence during 1 year in Spain are shown. It is noteworthy that although the DWTPs and WWTPs studied meet European and national regulations on water sanitary quality, both parasites were found in water samples from these plants, supporting the idea that new and appropriate controls and regulations for drinking water, wastewater, and recreational waters should be proposed to avoid health risks from these pathogens.

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 .