Emerging human pathogenic microsporidia in built-up environments: a public health concern?

Genera of the phylum of Microsporidia that have been categorised as emergent human pathogens include Enterocytozoon bieneusi and Encephalitozoon spp. (E. intestinalis, E. hellem and E. cuniculi). The sources of human infection and the routes of transmission of microsporidia are not yet fully understood, although a strong zoonotic component has been suggested, which may represent a serious public health concern in the built-up environment due to the presence of “urban animals”. We reported, for the first time, the presence of human-related microsporidia in 2 out of 18 dog faecal samples collected in public parks from the city centre of Leicester (England) in January 2016 during a pilot study. We report here the results of a further investigation performed from June 2016 to February 2017 in which 228 animal faecal samples were randomly collected from different parks and recreational areas across Leicester. Spores of microsporidia were observed in 36 of these samples by Weber’s modified trichrome stain analysis, which were subsequently processed by real time polymerase chain reaction (RT-PCR) with melting curve analysis for species identification. The RT-PCR assay indicated that 28 out of these 36 stools samples were positive for human-related microsporidia, as follows: Encephalitozoon spp. were detected in 26 of these faecal samples (14 deer, 7 avian [3 waterfowl, 2 songbird, 1 pigeon, 1 uncertain], 2 dog, 1 fox and 2 unidentified due to diarhoea), for which E. intestinalis/ E. hellem were specifically found in two (waterfowl and uncertain avian species) and E. cuniculi in 7 samples (6 deer and 1 fox). For its part, Enterocytozoon bieneusi was detected in 2 of them, both from waterfowl. Our results highlight that different urban animal species could play a role in the transmission of these pathogens that requires to be fully understood to develop interventions to protect the local community.