Untersuchungen zur saisonalen Aktivität der Buntzecke Dermacentor reticulatus im Umland von Berlin und Bestimmung assoziierter Pathogene
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Beschreibung
Investigation of the seasonal activity of the ornate tick Dermacentor reticulatus in the Berlin area and analyses of associated pathogens
Tick-borne pathogens increasingly gain importance in human and veterinary medicine. In Europe, Dermacentor reticulatus is the second most abundant tick species after Ixodes ricinus. An increasing geographic distribution of the tick species is observed due to the creation of appropriate habitats, enhanced transport of animals in the context of globalisation and climate change. Dermacentor reticulatus plays an important role in the transmission of different pathogens, especially in the field of veterinary medicine.
To assess the risk posed by D. reticulatus in the area of Berlin/Brandenburg this study focused on the investigation of the seasonal activity and the prevalence of different pathogens in this tick species. For this purpose, four periurban study sites around Berlin (Güterfelde, Gatow, Falkenberg, Königs Wusterhausen) were sampled biweekly using the flagging method in the period from March 2010 to November 2011. In comparison to I. ricinus (n=1020), D. reticulatus (n=8166) represented the dominant tick species. All collected D. reticulatus were exclusively identified as adult individuals. Moreover, a significantly higher proportion of female than male ticks were recognised at every sampling site. The tick species demonstrated a characteristic bimodal pattern of activity at every sampling site and year. Periods of high tick activity were observed from March to mid/end of May and from August to November. During summer months, the activity of ticks almost completely vanished. Sampling at the beginning of the year 2011 and additional samplings from December 2011 to April 2012 at the study site Güterfelde demonstrated tick activity even during winter months, although high variations in tick numbers were recorded. To identify potential impacts on tick activity by different variables (sampling site, year, season, temperature, relative humidity), multivariate analysis was performed using negative binomial regression analysis. As a result, tick activity was significantly influenced by the factors sampling site, season and temperature. The effect of temperature on the number of questing D. reticulatus differed depending on its level: up to an optimum value of 14.03 °C, tick activity increased with rising temperatures while tick activity declined with further temperature increase.
Out of all of collected ticks, a subset of 2000 female D. reticulatus was analysed for the presence of Babesia spp., Borrelia spp., Anaplasma spp., Ehrlichia spp., Candidatus Neoehrlichia mikurensis and Rickettsia spp. using different PCR assays. With the exception of Rickettsia, only low prevalences were documented. As few as 0.05 % (95 % confidence interval [95 % CI]: 0.01-0.28 %) and 0.25 % (95 % CI: 0.11-0.58 %) of ticks harboured Anaplasma spp. or Borrelia spp., respectively. The pathogens Babesia spp., Ehrlichia spp. and Cand. Neoehrlichia mikurensis were not detected (0 %, 95 % CI: 0-0.14 %). Sequencing of positive samples revealed Anaplasma phagocytophilum, Borrelia afzelii or Borrelia miyamotoi. To the best of the author’s knowledge, this is the first description of B. miyamotoi in D. reticulatus. The overall prevalence of Rickettsia (64 %, 95 % CI: 61.9-66.1 %) is one of the highest that has ever been described before in D. reticulatus. Sequencing of a subset of positive samples showed an infection with Rickettsia raoultii. With 71.5-78.3 % Rickettsia-infected ticks collected in Güterfelde, Falkenberg and Königs Wusterhausen, local prevalence were higher compared to only 31.4 % in Gatow. Using a general linearized logistic regression model, the factors sampling site, year and season were analysed for potential influences on prevalence of Rickettsia pathogens. Only the sampling site significantly affected the prevalence.
The study revealed endemic populations of D. reticulatus in the investigated sub-urban areas in and around the city of Berlin. Some of the sampling sites are even used as recreational areas. Moreover, people have to be aware about the potential risk of infestation by ticks even in colder periods of the year. Consequently, an appropriate tick prophylaxis throughout the year should be recommended. The relevance of the predominantly found pathogen R. raoultii has so far not been sufficiently investigated in veterinary medicine. However, in humans R. raoultii is described as the etiologic agent of SENLAT. Based on the results of this study, essential information was generated to assess the risk of D. reticulatus and pathogens transmitted by this tick in the area of Berlin/Brandenburg.
Autor*in
Mareen Kohn
Themen in »Untersuchungen zur saisonalen Aktivität der Buntzecke Dermacentor reticulatus im Umland von Berlin und Bestimmung assoziierter Pathogene«
Anaplasmataceae Babesia Berlin Berlin/Brandenburg Borrelia Buntzecke Dermacentor reticulatus Epidemiologie Ixodes ricinus Krankheitserreger Krankheitsüberträger Rickettsia Zecken Zeckenübertragene Krankheitserreger disease vectors