Presence and distribution of emerging human pathogens microsporidia in soils from Alcalá de Henares (Spain) according to their physicochemical properties.

Topsoils can be the source of a myriad of emerging biological hazards, enhanced by the exponential socioeconomic development. A population could potentially be exposed to these hazards, such as spores from the emerging group of parasites, microsporidia, when playing or spending time in urban parks and recreational areas. However, the presence of human-related microsporidia in topsoils, which include Enterocytozoon bieneusi and the Encephalitozoon species of E. intestinalis, E. hellem and E. cuniculi, has barely been studied despite increasing reports of infection by these organisms. We studied the potential distribution of these microsporidian species in urban/industrial areas in Alcalá de Henares (Spain). Sixty topsoil samples were collected from different areas in Alcalá; DNA was extracted from each sample using Fast-Prep for Soil kit after appropriate pre-concentration. A SYBR Green real-time polymerase chain reaction technique was used for simultaneous detection of these microsporidian species. Organic matter content (OM), pH and electric conductivity (EC) were determined in soil samples using previously described methods. E. intestinalis/hellem was detected in two soil samples collected in urban areas, and E. cuniculi in an industrial and an urban area. In contrast, E. bieneusi was not found in any soil sample. OM content was significantly higher in industrial soils; meanwhile pH and EC did not show any differences between areas. Our results would indicate a low prevalence and negligible distribution of human-related microsporidia in Alcalá. The logistic regression model performed showed that the physicochemical properties studied did not have any effect in the presence/absence of these spores, although our results are not definitive due to the limited presence of these pathogens. A better understanding of the presence and circulation of microsporidia in urban soils is necessary to assess the potential risks on the population.