Presence and distribution of Encephalitozoon spp. spores across different soil types

Abstract

Background and aims: The presence of Encephalitozoon spp. (E. intestinalis, E. hellem and E. cuniculi) in urban topsoils has been poorly studied despite increasing reports of infection in humans. The aim was to determine factors that could affect the presence/distribution of these species in Alcalá de Henares (Spain). Methods: 227 topsoil samples were collected in July 2017 across urban parks and green areas from: urban (155), industrial (60) and a public garden (12). DNA was extracted by disrupting the spores using Fast-Prep for Soil®, followed by SYBR Green real-time PCR. Urban/industrial areas were sub-divided into four and two areas to investigate distribution. Organic matter content (OM), pH, electric conductivity and the texture (percentages of sand, clay and silt) were also determined in the soils. Results: Encephalitozoon spp. were detected in 22 of the soil samples (16 urban, 6 industrial). The processes of the composting used for fertilising public gardens might have inactivated the potential presence of any spores. OM and silt were significantly higher in industrial vs. urban soils, meanwhile percentages of clay and sand were significantly higher in urban areas. Meanwhile E. cuniculi did not show any relationship with soil textural factors, E. intestinalis was associated with industrial soils that presented lower percentages of sand (14.5 vs. 21.7; p<0.001) and higher levels of silt (78.5 vs 64.9; p=0.023). Silt could provide adequate shade and moisture for the survival of the spores, meanwhile sand does not retain water well. E. intestinalis/E. hellem, species that could not be distinguish between them, were associated with urban soils with higher content of clay (19.02 vs. 11; p=0.020). Conclusions: Our results indicate a moderate effect of soil conditions and types in the prevalence and distribution of Encephalitozoon spp. spores in Alcalá’s topsoils, which could be used to reduce their presence.