Infections and mixed infections with the selected species of Borrelia burgdorferi sensu lato complex in Ixodes ricinus ticks collected in eastern Poland: a significant increase in the course of 5 years.

Angelina Wójcik-Fatla,Violetta Zając,Ewa Cisak,Jacek Dutkiewicz,Jacek Sroka,Anna Sawczyn

doi:10.1007/s10493-015-9990-4

Abstract

In the years 2008–2009 and 2013–2014, 1620 and 1500 questing Ixodes ricinus ticks, respectively, were examined on the territory of the Lublin province (eastern Poland). The presence of three pathogenic species causing Lyme disease was investigated: Borrelia burgdorferi sensu stricto, B. afzelii and B. garinii. The proportion of I. ricinus ticks infected with B. burgdorferi sensu lato showed a highly significant increase between 2008–2009 and 2013–2014, from 6.0 to 15.3 %. A significant increase was noted with regard to all types of infections with individual species: single (4.7–7.8 %), dual (1.2–6.6 %), and triple (0.1–0.9 %). When expressed as the percent of all infections, the frequency of mixed infections increased from 21.4 to 49.2 %. Statistical analysis performed with two methods (by calculating of odds ratios and by Fisher’s exact test) showed that the frequencies of mixed infections in most cases proved to be significantly greater than expected. The strongest associations were found between B. burgdorferi s. s. and B. afzelii, and between B. burgdorferi s. s. and B. garinii. They appeared to be highly significant (P < 0.0001) when assessed by two methods for 2013–2014, and for the sum of findings for both time periods. The proportions of the individual species detected in the mixed infections in 2008–2009 and 2013–2014 revealed highly significant increases for B. burgdorferi s. s. and B. garinii (from 33.9 to 71.1 % and from 18.2 to 82.9 %, respectively), and an insignificant decrease for B. afzelii (from 51.4 to 41.6 %). The proportions of the species B. burgdorferi s. s., B. afzelii and B. garinii (with combined single and mixed infections) for 2008–2009 and 2013–2014 were: 51.2/44.0 %, 30.6/24.9 % and 18.2/31.1 %, respectively. In conclusion, our results seem to indicate the detrimental trend of the increasing infection rate of I. ricinus ticks with B. burgdorferi s. l. in eastern Poland, and dramatic enhancement of mixed infections with individual species, which may result in mixed infections of humans and exacerbation of the clinical course of Lyme disease cases on the studied area.

Highlights

The spirochetes of Borrelia burgdorferi sensu lato complex, transmitted mostly by ticks belonging to Ixodes genus, cause Lyme borreliosis, a multisystemic disorder which is regarded as the most abundant tick-borne disease of humans worldwide, it only occurs in the northern hemisphere (Rizzoli et al 2014)
Within the period of 5 years under study, we observed on the territory of eastern Poland a highly significant, circa. 2.5-times, increase both in the prevalence of B. burgdorferi s. l. infection of I. ricinus ticks, and in the proportion of mixed infections which attained an exceptionally high level of nearly a half (49.1 %) of all infected ticks
Similar to the present work, these authors noted a significant growth of mixed infections between 2001 and 2007 in I. ricinus ticks collected in the Siebengebirge in Germany, and report on a similar increase in Ireland and Denmark (Schwarz et al 2012)

Summary

Introduction

The spirochetes of Borrelia burgdorferi sensu lato complex, transmitted mostly by ticks belonging to Ixodes genus, cause Lyme borreliosis, a multisystemic disorder which is regarded as the most abundant tick-borne disease of humans worldwide, it only occurs in the northern hemisphere (Rizzoli et al 2014). L. complex, of which at least 9 (B. burgdorferi sensu stricto, B. afzelii, B. garinii, B. valaisiana, B. spielmanii, B. bavariensis, B. bissettii, B. finlandensis, B. carolinensis, and B. lusitaniae) are present in Europe (Lommano et al 2012; Rizzoli et al 2014). Determining of the species spectrum occurring in the tick vectors and/or vertebrate hosts of B. burgdorferi s. Of special relevance is identification of the proportion of polymicrobial infections appearing in one tick or vertebrate host, which increase the severity of disease symptoms when transmitted to humans or animals (Ginsberg 2008; Lommano et al 2012). Polymicrobial infections may occur as mixed infections involving species of the same genus, such as different species of B. burgdorferi s. l. complex, or coinfections involving species of different genera, such as B. burgdorferi s. l. and other species causing human tick-borne diseases, such as Anaplasma phagocytophilum causing granulocytic anaplasmosis, Babesia microti or Babesia divergens causing babesiosis, Bartonella spp. causing bartonellosis, and Rickettsia spp. causing spotted fever (Lommano et al 2012)

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Results

Conclusion