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Journal of Clinical Microbiology, October 1999, p. 3390-3391, Vol. 37, No. 10
Clinical Laboratory,
Received 26 April 1999/Returned for modification 15 June
1999/Accepted 1 July 1999
Adult Ixodes ricinus ticks were collected in
Switzerland and tested for the presence of coinfection with
Borrelia burgdorferi sensu lato and the human granulocytic
ehrlichiosis (HGE) agent by real-time PCR. Of 100 ticks, 49% were
positive for B. burgdorferi and 2% were positive for the
HGE agent. The two HGE agent-positive ticks were also found to be
positive for B. burgdorferi.
Lyme borreliosis and human
granulocytic ehrlichiosis (HGE) are emerging infectious diseases
of both humans and animals that are transmitted by ticks. In
Switzerland, Ehrlichia phagocytophila has been identified in
cattle (11) and an agent with 100% homology in its 16S rRNA
gene to the agent of HGE has been detected in dogs (14) and
horses (15). HGE is a recently discovered syndrome in humans
(3) caused by an agent phylogenetically closely related to
E. phagocytophila and Ehrlichia equi and was
found in the United States and also in Europe (10).
Coexistence of antibodies to tick-borne pathogens, such as
Babesia microti, HGE agent, and Borrelia
burgdorferi, have been reported (7), indicating that humans and animals may be infected simultaneously by these pathogens through tick bites.
In the present study, 100 DNA samples of adult female ticks were
tested to find molecular evidence of coinfection with
B. burgdorferi and the HGE agent in Switzerland.
Tick collection.
A total of 100 adult Ixodes
ricinus ticks were collected in Wangen, Canton of Zurich,
Switzerland, a region with a sporadic occurrence of granulocytic
ehrlichiosis in animals caused by an HGE-like agent. The ticks were
collected with an umbrella that was covered with a terry cloth towel
and repeatedly pushed through the low underbrush in forests. Ticks
attached to the towel were removed, placed into tubes, and stored
individually at DNA extraction.
After thawing, ticks were placed in 200 µl
of buffered phosphate solution in an Eppendorf tube and mechanically
crushed with sterile scissors. DNA extraction was performed with a
QIAamp tissue kit (Qiagen, Basel, Switzerland) according to the
manufacturer's recommendations.
PCR and DNA sequencing.
All DNA samples were examined for the
presence of B. burgdorferi sensu lato by real-time TaqMan
PCR and for the presence of Ehrlichia of the E. phagocytophila genogroup (13). The
Borrelia-specific TaqMan PCR, designed for the inner
part of the flagellin gene, was carried out with the following
oligonucleotides (5'
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Molecular Evidence of Coinfection of Ticks with Borrelia
burgdorferi Sensu Lato and the Human Granulocytic Ehrlichiosis
Agent in Switzerland
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ABSTRACT
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20°C until DNA extraction was performed.
3'): forward primer B.398f,
GGGAAGCAGATTTGTTTGACA; reverse primer B.484r,
ATAGAGCAACTTACAGACGAAATTAATAGA, and probe B.421p,
ATGTGCATTTGGTTATATTGAGCTTGATCAGCAA. The agent of the
Borrelia TaqMan PCR reacted with Borrelia
species but not with 30 other bacterial species tested. This indicates
the high analytical specificity for Borrelia species of the
TaqMan PCR. The analytical sensitivity was 10 copies of a cloned PCR
product (6a). Negative controls included DNAs from 50 noninfected, laboratory-reared adult ticks of the I. ricinus
species that were purchased from the Institute of Zoology in
Neuchâtel (Switzerland). Borrelia- and
Ehrlichia-specific DNAs were verified by conventional
nested-PCR amplification and sequencing of the amplified products.
Visualization of the PCR amplification products was performed by
gel electrophoresis on 1.8% agarose gels. Single bands were purified
(QIAquick gel extraction kit; Qiagen), cloned with a TOPO TA cloning
kit (Invitrogen, NV, Leek, The Netherlands), and sequenced with a
fluorescence-based automated sequencing system (ABI 377 DNA sequencing;
Microsynth, Balgach, Switzerland).
Nucleotide sequence accession numbers. The sequence of the flagellin gene of the Borrelia-positive ticks has been deposited in GenBank under the accession no. AF127531 (B. burgdorferi sensu stricto) and AF127532 (B. afzelii). The sequence of the 16S rRNA gene of the HGE agent-positive ticks has been deposited in GenBank under the accession no. AF084907.
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ACKNOWLEDGMENTS |
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This work was supported by the United Bank of Switzerland "on behalf of a customer."
We gratefully acknowledge R. Wicki, PE Biosystems, Rotkreuz, Switzerland, for excellent technical support with the ABI Prism 7700.
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FOOTNOTES |
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* Corresponding author. Present address: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616. Phone: (530) 752-5032. Fax: (530) 752-0414. E-mail: cmleutenegger{at}ucdavis.edu.
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