TDK conference 2020

In Europe, ticks are among the most important transmitters (vectors) of pathogens causing diseases in domestic or wild animals and humans. While the occurrence of tick-borne bacteria and protozoan parasites are well-documented in Switzerland, the epidemiological situation might change rapidly. This is in part due to natural causes, such as the ongoing climate change which may result in northward spreading of tick species, but also because of human activity, i.e. inadvertent introduction of exotic tick species. The aim of our study was to collect ticks from various host species in Switzerland, to identify the tick species morphologically and molecularly, as well as to screen rare, hitherto not reported tick-borne pathogens in these samples. We also included rodent tissues in these anaylses.

In 2019-2020 altogether 176 ticks were collected from the vegetation, as well as form humans (n=17), dogs (n=23), cats (n=41), deer (n=8), a rabbit and a hedgehog at 25 locations in three counties of southern Switzerland. Sixty two rodent liver/spleen tissue DNA extracts (representing three species and further two genera) available from 2006 were also analysed retrospectively. Three tick species were indentified: Ixodes ricinus (n=169), Rhipicephalus sanguineus (n=6) and I. hexagonus (n=1). In contrast to companion animals (dogs, cats) subadult ticks (larvae and nymphs) predominated on humans, which is a highly significant association (P<0.0001). Molecular taxonomic analysis showed that R. sanguineus and I. hexagonus in southern Switzerland is genetically most closely related to conspecific ticks reported from Italy. All tick DNA extracts (n=141) and rodent tissue DNA extracts (n=62) were PCR negative for trypanosomes (recently reported in I. ricinus in Slovakia) and Occidentia/Orientia spp. (known to occur in ticks/rodents). However, from a rodent (Myodes glareolus) sample the sequence of Borrelia miyamotoi was succesfully amplified. This a zoonotic relapsing fever spirochete, transmitted from rodent/bird reservoirs to humans via the bite of hard ticks (in Europe mainly by I. ricinus). To the best of our knowledge, this is the first finding of B. miyamotoi in a rodent in Switzerland, and (taking into account the year of collection: 2006) in a chronological order this might be the first indication of B. miyamotoi in any rodent species in Europe.