IXODES RICINUS (ACARI: IXODIDAE) AND TICK-BORNE DISEASE: INNOVATIVE APPROACHES TO DETECT PATHOGENS IN THE VECTOR

Ixodes ricinus (Ixodidae family) is the most studied and well-known tick species in Europe. The specimens of this species can spread a wide range of infectious agents, resulting in significant consequences for both animal and human health. They play an essential role in the spread of several bacterial genera of human and animal relevance, such as Rickettsia spp., Coxiella spp., Anaplasma spp., Borrelia spp. and viruses belonging to the Flaviviridae group such as Tick-Borne Encephalitis Virus (TBEV). During my PhD period, I focused my study mainly on the aetiological agents of Lyme Borreliosis (LB), a multi-systemic inflammatory disease that can cause an immune response following the bacteria infection. The main aim of the project was to shed light on the identification of the species of Borrelia burgdorferi s.l. complex, in ticks, involved in the development of LB. Hence, the PhD project were subdivided in two main works: 1. Developing a reliable tool to identify the Borrelia bacteria at genus level (resulted in a publication, Chiappa et al., 2020). The method is based on the amplification of a fragment of the groEL gene. The obtained results suggest that this tool can represent a reliable method to perform epidemiological study aiming at indicating the prevalence of B. burgdorferi s.l. in I. ricinus and therefore the possible risk exposure for humans. 2. Developing a reliable, species-specific, time- and cost-effective tool (LyDet approach) able to identify the three main Borrelia spp. that can cause Lyme Borreliosis (B. burgdorferi, B. afzelii and B. garini, Chiappa et al., in preparation). Starting from the Borrelia spp. genomes available in Genbank a Roary analyses and then a Discriminant Analysis of Principal Components were carried out to select highly discriminant Open Reading Frames for each of the three species of interest. The primers were de novo designed on those unique fragments and they were validated comparing the results with 5S-23S rRNA sequencing test. The LyDet method was found to be a good identification tool with an accuracy of 88%, a precision of 97%, a sensitivity of 72% and a specificity of 100%. In parallel, during my three years of PhD I also co-worked in other projects aiming the TBPs detection methods; a screening to record the TBPs prevalence in the Ticino area has been carried out in 2018-2019, an RNA and DNA co-extraction method has been developed and published.