Risk of tick-borne zoonoses in urban green areas: a case study from Turin, northwestern Italy

Ticks are increasingly reported in urban and peri-urban areas, such as city parks or peri-urban forests, across Europe. Land use changes, like the transformation of natural ecosystems into residential or recreational areas, and the restoration of natural areas connectivity for biodiversity purposes, facilitate human contact with these vectors. We evaluated the infestation by Ixodid ticks and their infection by zoonotic agents in two natural reserves (La Mandria and Stupinigi) in the urban area of Turin, northwestern Italy, near to densely inhabited suburbs and consistently frequented by people. We monthly performed dragging in 15 sites during a three-year period (2012–2014). Over 4000 ticks were collected, belonging to the species: Ixodes ricinus, I. acuminatus, Dermacentor marginatus, D. reticulatus, and Haemaphysalis concinna. The tick burden in La Mandria, a park very rich in wildlife, was higher than in Stupinigi, which is surrounded by a grid of roads and cultivated fields. The occurrence of I. ricinus nymphs was mainly related to habitat diversity and seasonal variation but weakly influenced by wildlife presence. Conversely, the density of I. ricinus nymphs were effectively estimated by vegetation coverage, micro-climatic conditions, and the presence of large wildlife. Molecular analyses showed the infections by Borrelia burgdorferi s.l. (24.1 %), Anaplasma phagocytophilum (2.9 %), and Spotted Fever Group rickettsiae (30.4 %) in I. ricinus. Tick-borne encephalitis virus, that is considered so far absent in northwestern Italy, was not detected. In La Mandria, the risk of encountering one I. ricinus nymph infected by Borrelia burgorferi s.l. in 100 m2 was 59.1 % (95% Confidence Interval [CI]: 36.3–83.0), and 71.3 % (95%CI: 44.5–93.0) for Rickettsia spp. Educational programs on personal protection and surveillance on tick-borne diseases should be enhanced to face the threat posed by tick vectors in green urban landscapes.