Abstract
Seeking evidence to confirm that blackbirds (Turdus merula) may be involved in environmental maintenance of Borrelia burgdorferi s.l. (the causative agent of Lyme borreliosis), we conducted a long-term study over three separate 2-year periods, together embracing a span of almost 20 years, all in the same area in northeastern Poland. We examined a total of 78 blackbirds and collected 623 Ixodes ricinus ticks feeding on them. The tick infestation prevalence was found to be very high (89.7 %). Among all ticks collected, 9.8 % individuals were infected with B. burgdorferi s.l. spirochetes. We found statistically significant growth in the prevalence of infected ticks as well as an increasing proportion of blackbirds hosting them in subsequent years of study. Ticks feeding on blackbirds were infected mainly with B. garinii (45.7 %), a genospecies commonly encountered in birds, and with B. afzelii (28.6 %), until recently considered rodent-associated. We also identified B. turdi (22.9 %), frequently found in recent years in ticks feeding on birds, and B. spielmanii (2.8 %), which had previously not been found in infected ticks feeding on blackbirds. We also found that ticks infected with genospecies associated with avian reservoir groups (B. garinii and B. turdi) were not randomly distributed on blackbirds, but instead focused on certain bird specimens. We therefore conjecture that this is a result of ticks becoming infected either from the host blackbird itself, or from other infected ticks feeding on the same host blackbird. We did not find any similar dependency for the rodent specialist B. afzelii.Electronic supplementary materialThe online version of this article (doi:10.1007/s10493-016-0082-x) contains supplementary material, which is available to authorized users.
Highlights
Borrelia burgdorferi sensu lato (s.l.) is a genospecies complex of Gram-negative spirochete bacteria with a worldwide distribution
We identified B. turdi (22.9 %), frequently found in recent years in ticks feeding on birds, and B. spielmanii (2.8 %), which had previously not been found in infected ticks feeding on blackbirds
Of the 20 genospecies that have been identified to date, nine (B. afzelii, B. bavariensis, B. bissettii, B. burgdorferi s.s., B. garinii, B. kurtenbachii, B. lusitaniae, B. spielmanii and B. valaisiana) infect humans, causing Lyme borreliosis, which is a multisystem, tick-borne zoonosis with a wide spectrum of clinical manifestations (Margos et al 2011; Rudenko et al 2011; Ivanova et al 2014)
Summary
Borrelia burgdorferi sensu lato (s.l.) is a genospecies complex of Gram-negative spirochete bacteria with a worldwide distribution. The ixodid ticks have low mobility and are mainly dispersed by their host species. In their life cycle, ticks require vertebrate hosts, most frequently mammals, of which rodents and insectivores are the core group of hosts for immature ticks (larvae and nymphs), whereas carnivores and ungulates are the main hosts chosen by adult ticks (Kjelland et al 2011; Radzijevskaja et al 2013). Birds are the second group of vertebrates on which ixodid ticks can engorge. They, especially migratory species, may transport ticks over long distances and across geographical barriers, such as mountains, deserts or oceans, which would halt mammals. Many bird species throughout the world are infested with ticks and act as transport vehicles for these ectoparasites across a continent or from one continent to another during their seasonal migration (Olsen et al 1995b; Smith et al 1996; Gryczynska et al 2002; Hasle et al 2009)
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