Spatiotemporal dynamics of emerging pathogens in questing Ixodes ricinus

Abstract

Ixodes ricinus transmits Borrelia burgdorferi sensu lato, the etiological agent of Lyme disease. Previous studies have also detected Rickettsia helvetica, Anaplasma phagocytophilum, Neoehrlichia mikurensis, and several Babesia species in questing ticks in The Netherlands. In this study, we assessed the acarological risk of exposure to several tick-borne pathogens (TBPs), in The Netherlands. Questing ticks were collected monthly between 2006 and 2010 at 21 sites and between 2000 and 2009 at one other site. Nymphs and adults were analysed individually for the presence of TBPs using an array-approach. Collated data of this and previous studies were used to generate, for each pathogen, a presence/absence map and to further analyse their spatiotemporal variation. R. helvetica (31.1%) and B. burgdorferi sensu lato (11.8%) had the highest overall prevalence and were detected in all areas. N. mikurensis (5.6%), A. phagocytophilum (0.8%), and Babesia spp. (1.7%) were detected in most, but not all areas. The prevalences of pathogens varied among the study areas from 0 to 64%, while the density of questing ticks varied from 1 to 179/100 m2. Overall, 37% of the ticks were infected with at least one pathogen and 6.3% with more than one pathogen. One-third of the Borrelia-positive ticks were infected with at least one other pathogen. Coinfection of B. afzelii with N. mikurensis and with Babesia spp. occurred significantly more often than single infections, indicating the existence of mutual reservoir hosts. Alternatively, coinfection of R. helvetica with either B. afzelii or N. mikurensis occurred significantly less frequent. The diversity of TBPs detected in I. ricinus in this study and the frequency of their coinfections with B. burgdorferi s.l., underline the need to consider them when evaluating the risks of infection and subsequently the risk of disease following a tick bite.

Infections with the tick-borne bacterium Candidatus Neoehrlichia mikurensis

“…In Sweden, C. Neoehrlichia mikurensis infection among bank voles followed the same pattern: a monthly increase in infection rate was noted from May (8.7%) and in subsequent months, reaching a maximum in September (54%) [56]. Similarly, the highest rate of C. Neoehrlichia mikurensis infection of ticks was seen in October in The Netherlands [55].…”

“…C. Neoehrlichia mikurensis-infected ticks may be co-infected with other pathogenic species, such as Borrelia, Babesia, Rickettsia, and Anaplasma [14,26,28,31,44,49,56]. The rate of co-infection of ticks with C. Neoehrlichia mikurensis and Borrelia species is higher than predicted, and it may be more common for C. Neoehrlichia mikurensis to occur together with Borrelia than to appear alone in ticks [28,49,55]. This is probably a consequence of the feeding of ticks on rodents that are infected with both pathogens.…”

“…Most European studies have indicated that C. Neoehrlichia mikurensis is the third most common tick-borne human pathogen after Borrelia and Rickettsia species [33,44,55]. Estimates of the prevalence of C. Neoehrlichia mikurensis among ticks are shown in Table 1.…”

“…The prevalence of C. Neoehrlichia mikurensis seems to be increasing: a monthly surveillance study of infection rates of questing ticks conducted at 22 sites in The Netherlands between 2006 and 2010 revealed an increasing prevalence of C. Neoehrlichia mikurensis, in contrast to the stable prevalence rates of the other studied pathogens, including Rickettsia helvetica, Borrelia species, Babesia species, and A. phagocytophilum [55]. Although the first published report of this new species appeared in 1999 [3], these bacteria have been detected in a tick collection from 1960 [22].…”

Detection of ‘Candidatus Neoehrlichia mikurensis’ and other Anaplasmataceae and Rickettsiaceae in Canidae in Switzerland and Mediterranean countries

“…The occurrence of 'Candidatus Neoehrlichia mikurensis' in ticks may be on an upward trend (Coipan et al, 2013), and Neoehrlichosis has been recognized as a zoonosis. Thus, the improvement of routine diagnostic assays and raising the awareness of clinicians for this infection are important.…”