Borrelia miyamotoi and other tick-borne pathogens in a natural area recently colonized by ticks in the Western Alps, Italy

In Europe, Ixodid ticks are expanding their altitudinal range in mountain areas. In the Alpi Cozie regional park, Susa Valley, Western Italian Alps, ticks were very rarely found in the past years, while nowadays tick bites are increasingly reported, and three forestry workers were diagnosed with Lyme disease during spring-summer 2016. To evaluate the risk of tick bites and of infection by tick-borne pathogens in the area, we carried out a tick collection from May to October, 2016, in 45 dragging sites located between 950 and 1850 m altitude. A sample of nymphs was then analysed by PCR to evaluate the infection prevalence by bacterial zoonotic agents. All collected ticks were identified as Ixodes ricinus (1562 larvae, 918 nymphs and 32 adults). Wooded areas at 1000-1250 m altitude were the most infested, but ticks were encountered up to 1750 m; in tick-positive sites, the mean number of nymphs/100 m dragging varied from 0.3 to 24.5. Out of 365 tested nymphs, Borrelia miyamotoi was detected in two specimens (0.5%), being the first report of this emerging pathogen in Italy. We found Borrelia burgdorferi s.l. in 9.0% of the samples; the identified genospecies were B. afzelii and B. garinii. Spotted Fever Group rickettsiae were detected in 11.0% of the nymphs, namely R. helvetica and R. monacensis. Finally, we found Anaplasma phagocytophilum in 1.9% of the nymphs, and the three sequenced samples belonged to ecotype I. No Neoehrlichia mikurensis was detected. Since the presence of ticks and transmitted pathogens are new phenomena in the Western Alps, we are carrying out educational activities together with the park personnel to raise awareness on the danger posed by ticks and on the importance of avoiding their bites. Moreover, tick collection is ongoing, to evaluate environmental risk factors and monitor a possible further altitudinal increase of I. ricinus.