Supplementary materials of the Journal of the European Mosquito Control Association: Ixodes ricinus (Acari, Ixodidae) ticks and tick-borne pathogen prevalence on the Isle of Wight – an island perspective in southern England

Tick-borne disease incidence is predicted to increase over the next decade, so it is important to understand drivers of tick density and pathogen prevalence. Although deer are common reproduction hosts for Ixodes ricinus ticks, other reproduction hosts, such as livestock, can maintain tick populations as well. Here, we investigated tick density and their pathogen composition on a large island in southern England, where wild deer populations are reported to be extremely low. Questing ticks were collected in 2018 and 2021 from 26 publicly accessible rural woodland and grassland sites on the Isle of Wight (UK), and the questing nymphs (n=155) and adults (n=16) collected in 2021 were tested for a range of pathogens and endosymbionts. Questing nymph density was low overall in a range of natural habitats compared to the mainland, possibly due to the absence of significant wild deer populations on the island. Tick densities were significantly higher though in sites where natural grassland habitats were grazed by livestock, confirming the role that cattle and sheep play in driving tick abundance in natural habitats where deer density is low. Anaplasma phagocytophilum was detected in 40.6% of questing nymphs, some of the highest for the UK, whereas for other pathogens, infection rates were much lower: 1.3% for both Babesia divergens and Rickettsia helvetica and 0.6% for both Borrelia valaisiana and Borrelia miyamotoi. Rickettsiella (65.8%), Midichloria (63.9%) were also detected and their associations with known pathogens are discussed. We also detail the first report of Spiroplasma ixodetis (1.9%) in southern England. Our findings indicate that on the Isle of Wight, I. ricinus is at very low densities in most woodland habitats, where wild deer populations are low and livestock grazing is absent. It also illustrates that the density of Borrelia-infected I. ricinus is generally low, that livestock is the main propagation host for I. ricinus, and that other pathogens (A. phagocytophilum) are the predominant circulating tick-borne pathogens, notably on an island with low densities of wild deer.