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During its lifecycle, the generalist Ixodes ricinus takes up three blood meals from a wide selection of vertebrate hosts, some of which are reservoirs for multiple vector-associated pathogens. Since I. ricinus also readily bites humans, pets, and livestock, these hosts are at risk of becoming infected with more than one tick-borne pathogen. Multiple tick-borne infections are a public health concern, since they may increase diversity and duration of symptoms and complicate differential diagnosis and therapy. We used an existing Fluidigm real-time PCR chip to identify the minimum risk of exposure to infected/co-infected ticks in Denmark. We screened 509 nymphs and 504 adult female I. ricinus ticks for 17 different vector-associated pathogenic agents. The questing ticks were collected by flagging during the same season in two consecutive years in Grib forest in the capital region of Copenhagen. Overall, 19.1% of the nymphs and 52.2% of the adult female ticks harbored at least one zoonotic pathogen. The main agents were Borrelia spp., Anaplasma phagocytophilum and Rickettsia helvetica , while Candidatus Neoehrlichia mikurensis and Babesia venatorum both were present in less than 1% of the ticks. In 3.5% of the nymphs and 12.3% of adults we found more than one tick-borne pathogen. Of these, 15% were potentially triple or quadruple infections. Whereas mixed infections with Borrelia were equally distributed among both life stages, the adult ticks hosted 84.5% of the co-infections with different species of tick-borne pathogens, chiefly involving Borrelia species in combination with either R. helvetica or A. phagocytophilum. Statistical analyses indicated non-random co-occurrence of Borrelia spielmanii/Borrelia garinii in both life stages and B. garinii / Borrelia afzelii and B. garinii / Borrelia valaisiana in the nymphs. Although the overall prevalence of ticks hosting more than one infection only constituted 7.9% at the particular site investigated in this study, our results still underline that co-infections should be considered in diagnosis and treatment of tick-borne diseases in northern Europe. [ABSTRACT FROM AUTHOR]

Abstract Presently, it is uncertain to what extent seasonal migrating birds contribute to the introduction of ticks and tick-associated pathogens in Denmark. To quantify this phenomenon, we captured birds during the spring and autumn migration at three field sites in Denmark and screened them for ticks. Bird-derived ticks were identified to tick species and screened for 37 tick-borne pathogens using real-time PCR. Overall, 807 birds, representing 44 bird species, were captured and examined for ticks during the spring (292 birds) and autumn migrations (515 birds). 10.7% of the birds harboured a total of 179 Ixodes ricinus ticks (38 ticks in spring and 141 in the autumn) with a mean infestation intensity of 2.1 ticks per bird. The European robin (Erithacus rubecula), the common blackbird (Turdus merula), and the common redstart (Phoenicurus phoenicurus) had the highest infestation intensities. 60.9% of the ticks were PCR-positive for at least one tick-borne pathogen. Borrelia DNA was found in 36.9% of the ticks. The Borrelia species detected were B. spielmanii (15.1%), B. valaisiana (13.4%), B. garinii (12.3%), B. burgdorferi s.s. (2.2%), B. miyamotoi (1.1%), and B. afzelii (0.6%). In addition, 10.6% and 1.7% of the samples were PCR-positive for spotted fever group rickettsiae and Candidatus Neoehrlichia mikurensis. All of the tick-borne pathogens that we found in the present study are known to occur in Danish forest populations of I. ricinus. Our study indicates that migrating birds can transport ticks and their pathogens from neighboring countries to Denmark including sites in Denmark without a sustainable tick population. Thus, a tick-borne pathogen affecting human or animal health emerging at one location in Europe can rapidly be introduced to other countries by migrating birds. These movements are beyond national veterinary control. The current globalization, climatic and environmental changes affect the potential for introduction and establishment of ticks and tick-borne pathogens in Northern Europe. It is therefore important to quantify the risk for rapid spread and long distance exchange of tick-borne pathogens in Europe. [ABSTRACT FROM AUTHOR]