Lyme disease in ticks in the Chicago area

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http://www.cdc.gov/ncidod/EID/vol12no06/06-0306.htm

Emerging Infectious Diseases
Vol. 12, No. 6
June 2006

Letter

Borrelia burgdorferi in Ixodes scapularis Ticks, Chicago Area

Dean A. Jobe,* Steven D. Lovrich,* Jeffrey A. Nelson,? Tom C.
Velat,? Chris Anchor,§ Tad Koeune,¶ and Stephen A. Martin, Jr#
*Gundersen Lutheran Medical Center, La Crosse, Wisconsin, USA;
?North Park University, Chicago, Illinois, USA; ?Forest Preserve
District of DuPage County, Wheaton, Illinois, USA; §Forest Preserve
District of Cook County, Elgin, Illinois, USA; DuPage County
Department of Health, Wheaton, Illinois, USA; and #Cook County
Department of Public Health, Oak Park, Illinois, USA

Suggested citation for this article

To the Editor: Lyme disease is a multisystem disorder associated
with skin, myocardial, musculoskeletal, and central and peripheral
nervous system manifestations caused by infection with Borrelia
burgdorferi sensu lato spirochetes (1). In the United States, the
illness is caused by transmission of B. burgdorferi sensu stricto
from the bite of infected Ixodes scapularis (deer) ticks found
primarily in the northeastern and upper midwestern United States
(2). B. burgdorferi-infected ticks have also been recovered in
portions of northern Illinois but have not yet been reported in the
Chicago region (3). In fact, a previous survey (4) of forested areas
in the heavily populated regions immediately adjacent to Chicago
confirmed a low risk of contracting Lyme disease. Researchers failed
to recover deer ticks from 7 sampling sites and recovered only a
single Borrelia isolate from well-described B. burgdorferi sensu
stricto rodent reservoirs (mice, voles, chipmunks) captured from 5
sampling sites. A subsequent genetic analysis confirmed the isolate
was B. bissettii (5), a genomic group that is likely nonpathogenic
to humans in the United States.

However, the area of the Midwest where Lyme disease is endemic has
continued to expand from its origin in northeastern Minnesota and
northwestern Wisconsin (2,6). The Chicago metropolitan region has
numerous parks and natural areas that are biologically similar to
the known midwestern focus (7), and these areas support a large
population of white-tailed deer. Moreover, we have seen anecdotal
reports of persons with clinical signs and symptoms of Lyme disease
and epidemiologic evidence that suggests local acquisition. Two
ticks submitted by a resident who had hiked in DuPage County near
the east branch of the DuPage River were I. scapularis. We therefore
began searching for questing ticks in this area and 9 other
geographically diverse areas of DuPage County. The 10 sites were
flagged by dragging white cotton sheets through the underbrush for 2-
to 10-hour intervals during the spring of 2005. We timed these
collections on the basis of information that adult deer ticks were
questing in Wisconsin. Recovered ticks were placed in sealed vials
and transported to the North Park University Laboratory where their
identity was confirmed. The midguts were then removed aseptically,
and each was placed into a separate vial that contained 2 mL
modified Barbour-Stoenner-Kelly medium that could support the growth
of small numbers of B. burgdorferi sensu stricto ( Cool

. Cultures were
incubated for 6 weeks at 35°C and examined weekly for spirochetes by
darkfield microscopy.

Deer ticks were not found at 8 of the DuPage County sample sites.
However, 90 adult or nymphal I. scapularis were collected from the
remaining 2 sites, and spirochetes were recovered from 3 (3%) of the
tick midgut cultures. Because of these findings and anecdotal
reports of deer ticks in Cook County, we also surveyed 3 sites in
Cook County during the fall of 2005. Deer ticks were not found at 2
sites, but 37 adult I. scapularis ticks were collected from a site
in the southwestern portion of Cook County, and spirochetes were
recovered from 2 (5%) cultures.

[Figures omitted on LymeInfo - go to URL at top of page to view
figure captioned below.]
Figure. Protein profiles of Borrelia burgdorferi sensu stricto (lane
A), B. bissettii (lane B), and spirochetes...

We first examined the protein profiles to identify the spirochetes.
Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses
of 4 of the 5 isolates (1 isolate lost viability before analysis)
showed that they were distinctly different from the B. bissettii
isolate recovered previously from Cook County (4), but the isolates
were strikingly similar to B. burgdorferi sensu stricto (Figure). We
then amplified an intergenic spacer region of the rrf-rrl portion of
the rRNA from 2 isolates by a previously described method (9) and
sequenced the amplified products (sequencing by Laragen, Inc., Los
Angeles, CA, USA). The sequences were identical to that of B.
burgdorferi sensu stricto isolate B-31 (9).

The results confirmed that I. scapularis ticks infected with B.
burgdorferi sensu stricto were recovered from forested areas
surrounding Chicago. Additional studies to define the extent and
severity of the risk are necessary, but clinicians and the public
should be aware of the possibility of acquiring Lyme disease in the
Chicago metropolitan region.

Acknowledgments

We thank Joan Bestudik and Linn D. Haramis for initiating the
project; John and Tammie Bouseman, Mike O'Driscoll, Curt Colwell,
Barb O'Meara, Peter Gianakis, Rachael Griffin, and our 16 student
participants for fieldwork; John Bouseman for tick identification;
and Steve Callister for guidance and manuscript review.

Partial funding for this work was received from the DuPage County
Health Department (to J.A.N.).

References

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disease): molecular and cellular pathobiology and prospects for
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2. Centers for Disease Control and Prevention. Lyme disease-United
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8. Callister SM, Case KL, Agger WA, Schell RF, Johnson RC, Ellingson
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9. Postic D, Ras NM, Lane RS, Henderson M, Baranton G. Expanded
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Suggested citation for this article:

Jobe DA, Lovrich SD, Nelson JA, Velat TC, Anchor C, Koeune T, et al.
Borrelia burgdorferi in Ixodes scapularis ticks, Chicago area
[letter]. Emerg Infect Dis [serial on the Internet]. 2006 Jun [date
cited]. Available from http://www.cdc.gov/ncidod/EID/vol12no06/06-
0306.htm

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