Acanthamoeba spp. in public parks’ soils in Spain: presence, distribution and risks

Abstract

Background and aims: Acanthamoeba spp. is a protozoan that is becoming a public health threat. This parasite has been isolated in stray cats from Madrid (Spain), which could play a role in contaminating urban environments. The aim was to determine the presence/distribution of Acanthamoeba spp. in Alcalá de Henares (a major city in the Madrid Region) to identify potential risks. Methods: 227 topsoil samples were collected in July 2017 across urban parks/green areas (155), industrial (60) and a public garden (12). Following extraction of DNA with FastDNA® Spin, a triplex real-time TaqMan PCR assay was performed to detect Acanthamoeba spp., using established methodologies. Organic matter (OM), pH, electric conductivity (EC) and texture (sand, clay and silt percentages) were also determined in soils. Results: Acanthamoeba spp. was detected in 39 topsoil samples, which suggests a moderate distribution throughout Alcalá. Higher presence in the urban (24) area could be explained by the major presence of urban animals, such as stray cats, in this area. The presence of cysts would have not been affected by the OM, pH or EC, despite variations seen in the levels of OM in the studied soils. In contrast to sand and silt, Acanthamoeba spp. seem to be more present in the areas with lower percentages of clay (13.76 detected vs. 18.38 not detected; p=0.006), association which has also observed within the four sub-areas in which the urban area was divided (p=0.016). Clay has more water holding capacity than sand and silt, so it would have been expected to find Acanthamoeba positively associated with clay, although its lower permeability might affect their survival. Conclusions: The low-moderate distribution of Acanthamoeba spp. detected could highlight a risk for the Alcalá population which should be further investigated as this protozoan can affect immunocompromised/immunocompetent individuals. Key words: Acanthamoeba, urban soils, human risks