New molecular tools for the study of the sheep tick (I. ricinus L.): development, application and epidemiological implications

The sheep tick, Ixodes ricinus, is the most important zoonotic vector in Europe; its dispersal potential and the relative importance of various vertebrate hosts it exploits, both essential to understand emergence of tick-borne diseases are virtually unknown. I applied two molecular approaches to 30 I. ricinus populations in the Province of Trento, Italy. A novel bloodmeal analysis Real-time HRMA protocol was developed and tested on questing nymphs. RAD-Seq was used for the first time on I. ricinus to individually genotype SNP loci in adult ticks. Bloodmeal analysis confirmed that rodents feed about 30% of tick larvae, but also illustrate that large mammals play a central role in feeding larval ticks. Since birds also feed about 15% ticks, the results of this analysis imply that larval ticks are carried long distances by their hosts; hence dispersal potential is high. In fact, population genetics support that investigated alpine populations are genetically admixed, confirming other phylogenetic studies showing that panmixia of I. ricinus population is a general phenomenon. This is the first study showing that dogs are important sheep tick hosts. As dogs feed a higher proportion of ticks in peri-urban forest, they may enhance the contact rate between human and infected ticks, by bringing them into human habitations and urban parks. My results have added new knowledge to tick dispersal and host use, which will be used to improve models of the spread of I. ricinus, and related pathogens, in new climatically suitable areas. My novel bloodmeal analysis protocol, which eliminates previous problems of contamination, could help to identify and explain local TBD dynamics in other areas of the EU