Attachment sites of different life stages of Ixodes ricinus ticks and infection of tick-borne pathogens in roe deer, badger, red fox and squirrel

As an effect of climate change and alterations in land use, the ranges of roe deer and also that of their ectoparasites, like the sheep tick (Ixodes ricinus) are expanding. This has also increased the occurrence of tick-borne pathogens that can be transmitted to humans and livestock, such as Borrelia burgdorferi sensu lato (s.l.) causing Lyme borreliosis in humans and Anaplasma phagocytophilum causing livestock fever in sheep and cattle. The impact of larger host animals on the transmission cycles for tick-borne pathogens has not been fully clarified. This study aims to contribute to add more knowledge on this subject by examining roe deer (Capreolus capreolus, n = 29), badgers (Meles meles, n = 14), red foxes (Vulpes vulpes, n = 6), and squirrels (Sciurus vulgaris, n = 17) for ticks. All data came from the municipality of Vestby, Moss and Frogn in Akershus (Viken, Norway) east of the Oslo fjord. I registered where ticks were located, in which stages of life, their number and on which animals they were attached. Tissue from all mammals were screened for the tick-borne pathogens B. burgdorferi s.l. and A. phagocytophilum. Roe deer had a prevalence of 100% for attached ticks. Adult ticks dominate on every part and especially on the back and the neck. Most of the nymphs are found on legs while larvae are mainly situated on head and legs. Roe deer had a high prevalence of 82% for A. phagocytophilum, but no B. burgdorferi s.l. infection. Badgers and red foxes had a prevalence for ticks of respectively 71% and 100% and with an intensity (ticks/individual) of 1.40 for badgers and 2.94 for red foxes. B. burgdorferi s.l. was found in both badger and red fox, and also a small amount of A. phagocytophilum with a 14% prevalence for badgers and 17% for red foxes for both pathogens. The red foxes had a high prevalence (69%) of dead, subcutaneous ticks. The squirrels had a high proportion of B. burgdorferi s.l., surprisingly no A. phagocytophilum. This makes the squirrels an efficient host for the transmission cycles for B. burgdorferi s.l.. My results show that the roe deer was the most competent host for in particular adult ticks, as evidenced from both prevalence (%), density and proportion of adult ticks, while squirrels mostly were an important host for nonadult ticks. Badgers seemed not significant for the tick’s lifecycle. The high occurrence of dead, subcutaneous ticks in red fox indicate a low host competence. Other large-sized hosts thus seemed less competent hosts to ticks than roe deer. Hence, this provide further evidence that deer density is one key to limitation of tick-borne diseases, and hence of considerable management interest.