A 10-year surveillance of Rickettsiales (Rickettsia spp. and Anaplasma phagocytophilum) in the city of Hanover, Germany, reveals Rickettsia spp. as emerging pathogens in ticks

Katrin Blazejak,Christina Strube,Elisabeth Janecek

doi:10.1186/s13071-017-2537-2

Katrin Blazejak, Christina Strube + Show 1 more

Open Access

https://doi.org/10.1186/s13071-017-2537-2

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Abstract

BackgroundRickettsiales (Rickettsia spp. and Anaplasma phagocytophilum) transmitted by ticks are considered (re-)emerging pathogens posing a risk to public health. Nevertheless, year-long monitoring studies on prevalences of these pathogens in questing ticks to contribute to public health risk assessment are rare.MethodsThe current study extends previous prevalence surveillances (2005 and 2010) by 2015 to a 10-year monitoring. Therefore, 2100 questing Ixodes ricinus were collected from April to October 2015 at ten different recreation sites in the city of Hanover, Germany, to determine potential changes in tick infection rates with Rickettsiales.ResultsOf the collected ticks, 288 were adult females, 285 adult males and 1527 nymphs. Overall, 3.8% (79/2100) of ticks were infected with A. phagocytophilum, 50.8% (1066/2100) with Rickettsia spp. and 2.2% (46/2100) with both pathogens. Statistical analyses revealed stagnating A. phagocytophilum infection rates over the 10-year monitoring period, whereas Rickettsia infections increased significantly (33.3% in 2005 and 26.2% in 2010 vs 50.8% in 2015). This increase was also characterized by prominent seasonality with higher prevalences from July to October.ConclusionsAs increased tick infection rates result in an increased risk for public health, the long-term data reported here provide significant implications for the understanding of progressing Rickettsiales distribution in ticks and essentially contribute to reliable public health risk assessments.

Highlights

Rickettsiales (Rickettsia spp. and Anaplasma phagocytophilum) transmitted by ticks are considered emerging pathogens posing a risk to public health
Case reports of human granulocytic anaplasmosis (HGA) from Europe are sporadic with identification of different strains, resulting in less severe disease [4,5,6,7]
Several studies determined tick infection rates with named pathogenic microorganisms [1, 8,9,10,11,12,13, 19]; periodically performed long-term monitoring studies based on a comparable set-up are scarce, even though such data are needed for a continuous public health risk assessment

Summary

Introduction

Rickettsiales (Rickettsia spp. and Anaplasma phagocytophilum) transmitted by ticks are considered (re-) emerging pathogens posing a risk to public health. Tick-borne diseases may have considerable impact on human and animal health. In central Europe, the widespread castor bean tick Ixodes ricinus transmits a variety of bacterial pathogens such as Anaplasma phagocytophilum or different Rickettsia species of the spotted fever group, which are considered (re-)emerging pathogens [1]. Both microorganisms are classified as Gram-negative, obligate. Estimated seroprevalences of antibodies against A. phagocytophilum appear to be considerably higher in contrast to prevalences in questing ticks. A. phagocytophilum induced tick-borne fever causes considerable economic losses due to clinical manifestations such as abortion, reduced milk production or sudden death [3]

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