Distribution and prevalence of Borrelia burgdorferi sensu latu genospecies, Anaplasma phagocytophilum and Babesia divergens in Irish questing nymphal ticks

Ixodes ricinus is an important vector of various pathogens of medical and veterinary importance in western Europe, including bacteria, protozoa and viruses. In Ireland, there has never been a national survey of ticks or tick-borne diseases. I. ricinus is the only exophilic tick present on the island, and it is the primary vector of borreliosis, babesiosis, anaplasmosis and Louping ill. This study aimed to optimise molecular assays and employ them to investigate the distribution and prevalence of different Borrelia species, Babesia divergens and Anaplasma phagocytophilum in I. ricinus nymphs collected from woodland sites and farms throughout Ireland between 2017 and 2019. Chapter 1 summarised the most important tick species worldwide and in Ireland, their life cycle and the most important tick-borne diseases. It also describes the most recent molecular assays used to investigate tick-borne pathogens and microbiomes and discusses strategies used to control ticks and tick-borne diseases. Chapter 2 investigated the distribution and prevalence of different B. burgdorferi s.l. genospecies in Irish I. ricinus nymphs using TaqMan and nested PCRs. In agreement with previous reports from Ireland we found a higher prevalence of Borrelia spp in woodland sites compared to farms which may be due to higher numbers of potential reservoir hosts in the former. Chapter 3 investigated the distribution and prevalence of Babesia divergens and Anaplasma phagocytophilum using optimised molecular assays. The results also showed a higher prevalence of A. phagocytophilum in woodland ticks compared to those collected from farm sites. In contrast the prevalence of B. divergens was higher in ticks collected farms confirming that cattle are the primary hosts for B. divergens. It is suggested for future research to investigate the presence of other pathogens not included in this study and to examine the role of different potential reservoir hosts to get a better understanding of tick-borne pathogens and their enzootic cycles in Ireland.