Prevalence of Borrelia burgdorferi and Granulocytic and ixodes ricinus

J
OURNAL OF
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LINICAL
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ICROBIOLOGY
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0095-1137/99/$04.00 1 0
Nov. 1999, p. 3448–3451 Vol. 37, No. 11
Copyright © 1999, American Society for Microbiology. All Rights Reserved.
Prevalence of Borrelia burgdorferi and Granulocytic and
Monocytic Ehrlichiae in Ixodes ricinus Ticks
from Southern Germany
BIRGIT U. BAUMGARTEN, MARTIN RO
¨
LLINGHOFF,
AND
CHRISTIAN BOGDAN*
Institute of Clinical Microbiology, Immunology and Hygiene, University of Erlangen, Erlangen, Germany
Received 29 March 1999/Returned for modification 8 July 1999/Accepted 29 July 1999
A total of 287 adult Ixodes ricinus ticks, collected in two regions of southern Germany (Frankonia and
Baden-Wu ¨rttemberg) where Borrelia burgdorferi infections are known to be endemic, were examined for the
presence of 16S ribosomal DNA specific for the Ehrlichia phagocytophila genogroup, E. chaffeensis , E. canis , and
B. burgdorferi by nested PCR. Totals of 2.2% (6 of 275) and 21.8% (65 of 275) of the ticks were positive for the
E. phagocytophila genogroup and B. burgdorferi , respectively. Two ticks (0.7%) were coinfected with both
bacteria. Of 12 engorged I. ricinus ticks collected from two deer, 8 (67%) were positive for the E. phagocytophila
genogroup and one (8%) was positive for B. burgdorferi . There was no evidence of infection with E. canis or E.
chaffeensis in the investigated tick population. The nucleotide sequences of the 546-bp Ehrlichia PCR products
differed at one or two positions from the original sequence of the human granulocytic ehrlichiosis (HGE) agent
(S.-M. Chen, J. S. Dumler, J. S. Bakken, and D. H. Walker, J. Clin. Microbiol. 32:589–595, 1994). Three groups
of sequence variants were detected; two of these were known to occur in other areas in Europe or the United
States, whereas one has not been reported before. Thus, in the German I. ricinus tick population closely related
granulocytic ehrlichiae are prevalent, which might represent variants of E. phagocytophila or the HGE agent.
Microorganisms of the tribe Ehrlichieae are obligate intra-
cellular bacteria that reside within cytoplasmic vacuoles
(phagosomes) of monocytes, granulocytes, or platelets of var-
ious mammalian species. Presently, the genus Ehrlichia can be
divided into three distinct clusters based on the nucleotide
sequence homology of the 16S rRNA genes (1, 11). These
genogroups carry the name of the group member that was first
characterized: Ehrlichia canis group ( E. canis , E. chaffeensis ,
E. muris , and E. ewingii ), Ehrlichia phagocytophila group ( E.
phagocytophila , E. equi , human granulocytic ehrlichiosis [HGE]
agent, and E. platys ), and Ehrlichia sennetsu group ( E. sennetsu
and E. risticii ). E. canis was originally described as a pathogen
in 1935, when an outbreak was observed among experimental
Algerian dogs (10). In 1953, E. sennetsu was the first ehrlichial
agent shown to be pathogenic for humans (20). To date, how-
ever, the mononucleosis-like Sennetsu fever rarely occurs out-
side Japan. More recently, two new ehrlichial organisms, which
elicit illnesses with fever, leukopenia, and thrombocytopenia in
humans, were found in the United States. E. chaffeensis , the
cause of human monocytic ehrlichiosis, was discovered in 1986
(1, 18), and the HGE agent was first reported in 1994 (7).