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Applied and Environmental Microbiology, May 2009, p. 3230-3237, Vol. 75, No. 10
0099-2240/09/$08.00+0 doi:10.1128/AEM.00220-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Molecular Investigations of Rickettsia helvetica Infection in Dogs, Foxes, Humans, and Ixodes Ticks
Felicitas S. Boretti,2*
Andrea Perreten,2
Marina L. Meli,1
Valentino Cattori,1
Barbara Willi,1,2
Nicole Wengi,1
Sándor Hornok,3
Hanspeter Honegger,4
Daniel Hegglin,5
Roman Woelfel,6
Claudia E. Reusch,2
Hans Lutz,1 and
Regina Hofmann-Lehmann1
Clinical Laboratory, Vetsuisse Faculty, University of Zurich, Switzerland,1 Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Switzerland,2 Department of Parasitology and Zoology, Faculty of Veterinary Science, Szent István University, Budapest, Hungary,3 Clinic of Medical Oncology, Triemli Hospital, Zurich, Switzerland,4 Institute of Parasitology, Vetsuisse Faculty, University of Zurich, Switzerland,5 Bundeswehr Institute of Microbiology, Munich, Germany6
Received 30 January 2009/ Accepted 16 March 2009
Rickettsia helvetica, a tick-borne member of the spotted-fever-group rickettsiae, is a suspected pathogen in humans; however, its role in animals is unknown. The aims of this study were to establish a R. helvetica-specific real-time TaqMan PCR assay and apply it to the analysis of tick vectors (to determine potential exposure risk) and blood samples from Canidae and humans (to determine prevalence of infection). The newly designed 23S rRNA gene assay for R. helvetica was more sensitive than a published citrate synthase gene (gltA) assay for several rickettsiae. Blood samples from 884 dogs, 58 foxes, and 214 human patients and 2,073 ticks (Ixodes spp.) collected from either vegetation or animals were analyzed. Although the maximal likelihood estimate of prevalence was 12% in unfed ticks and 36% in ticks collected from animals, none of the 1,156 blood samples tested PCR positive. Ticks from cats were more frequently PCR positive than ticks from dogs. Sequencing of the 23S rRNA and/or the gltA gene of 17 tick pools confirmed the presence of R. helvetica. Additionally, Rickettsia monacensis, which has not been previously found in Switzerland, was identified. In conclusion, R. helvetica was frequently detected in the tick population but not in blood samples. Nevertheless, due to the broad host range of Ixodes ticks and the high rate of infestation with this agent (i.e., R. helvetica was 13 times more frequent in unfed ticks than the tick-borne encephalitis virus), many mammals may be exposed to R. helvetica. The PCR assay described here represents an important tool for studying this topic.
* Corresponding author. Mailing address: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland. Phone: 41 (44) 635 81 12. Fax: 41 (44) 635 89 20. E-mail: fboretti{at}vetclinics.uzh.ch
Published ahead of print on 27 March 2009.
Applied and Environmental Microbiology, May 2009, p. 3230-3237, Vol. 75, No. 10
0099-2240/09/$08.00+0 doi:10.1128/AEM.00220-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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