Content uploaded by Kerry Padgett
Author content
All content in this area was uploaded by Kerry Padgett on Mar 02, 2018
Content may be subject to copyright.
This article appeared in a journal published by Elsevier. The attached
copy is furnished to the author for internal non-commercial research
and education use, including for instruction at the authors institution
and sharing with colleagues.
Other uses, including reproduction and distribution, or selling or
licensing copies, or posting to personal, institutional or third party
websites are prohibited.
In most cases authors are permitted to post their version of the
article (e.g. in Word or Tex form) to their personal website or
institutional repository. Authors requiring further information
regarding Elsevier’s archiving and manuscript policies are
encouraged to visit:
http://www.elsevier.com/copyright
Author's personal copy
Ticks
and
Tick-borne
Diseases
2 (2011) 191–
195
Contents
lists
available
at
ScienceDirect
Ticks
and
Tick-borne
Diseases
journa
l
h
o
mepage:
www.elsevier.de/ttbdis
Original
Article
Novel
exposure
sites
for
nymphal
Ixodes
pacificus
within
picnic
areas
Kerry
A.
Padgett∗, Denise
L.
Bonilla
Vector-Borne
Disease
Section,
Infectious
Diseases
Branch,
Division
of
Communicable
Disease
Control,
Center
for
Infectious
Diseases,
California
Dept.
of
Public
Health,
850
Marina
Bay
Parkway,
Richmond,
CA
94804,
USA
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
25
February
2011
Received
in
revised
form
11
July
2011
Accepted
13
July
2011
Keywords:
Ixodes
pacificus
Picnic
areas
Ixodes
auritulus
Borrelia
bissettii
Lyme
disease
Borrelia
miyamotoi
a
b
s
t
r
a
c
t
Risk
of
exposure
to
nymphal
Ixodes
pacificus
Cooley
and
Kohls
ticks
was
investigated
at
7
picnic
areas
in
Tilden
Regional
Park,
a
heavily
used
recreation
area
of
over
2000
acres
in
northwestern
California,
east
of
San
Francisco
Bay.
Wooden
picnic
tables,
tree
trunks,
logs,
leaf
litter,
surrounding
vegetation,
and
rock
walls
were
checked
for
ticks
using
standard
1-m2flannel
tick
flags
at
biweekly
intervals
from
March
to
August
2008.
Results
indicate
that
nymphal
I.
pacificus
were
commonly
found
on
wooden
picnic
tables
and
other
wooden
materials,
such
as
tree
trunks
and
logs,
at
an
equal
proportion
to
those
found
in
leaf
litter.
Nymphal
I.
pacificus
in
picnic
areas
peaked
in
April,
with
a
secondary
peak
in
early
June.
Five
of
170
(2.9%)
nymphal
I.
pacificus
collected
at
picnic
sites
were
positive
for
Borrelia
spirochetes,
of
which
3
(1.8%)
were
identified
as
B.
burgdorferi
sensu
stricto
using
molecular
techniques.
In
addition,
a
nymphal
I.
auritulus
collected
from
a
rock
wall
in
a
picnic
area
tested
positive
for
a
mixture
of
B.
burgdorferi
and
B.
bissettii;
this
tick
species
feeds
exclusively
on
birds.
This
study
indicates
a
moderate
risk
of
acquiring
a
nymphal
tick
at
Tilden
Park
picnic
areas,
but
due
to
the
low
B.
burgdorferi
infection
prevalence,
the
risk
of
acquiring
Lyme
disease
appears
to
be
low.
Published by Elsevier GmbH.
Introduction
The
nymphal
stage
of
the
western
blacklegged
tick,
Ixodes
paci-
ficus
Cooley
and
Kohls
is
the
primary
vector
of
Lyme
disease
in
western
North
America.
Due
to
its
small
size,
it
is
often
not
noticed
by
humans,
but
has
a
relatively
high
infection
prevalence
compared
to
the
adult
stage
(Clover
and
Lane,
1995).
Furthermore,
the
time
of
year
when
I.
pacificus
nymphs
are
active
(spring
and
early
sum-
mer)
compared
to
the
adult
stage
(winter)
coincides
with
increased
outdoor
activity,
either
peridomestically
or
in
recreational
areas.
In
California,
approximately
half
the
reported
cases
of
Lyme
dis-
ease
are
acquired
during
outdoor
activities
outside
the
individuals’
county
of
residence
(CDPH,
unpubl.
results).
Recreational
activities,
such
as
hiking
on
established
trails,
appear
to
present
a
low
risk
in
terms
of
acquiring
I.
pacificus,
in
northern
California
(Lane,
1996;
Li
et
al.,
2000).
On
the
other
hand,
woodcutting
was
previously
associated
with
Lyme
disease
cases
in
northern
California
(Lane
et
al.,
1992),
and
contact
with
wood
by
sitting
or
leaning
on
logs
or
tree
trunks
has
been
shown
to
increase
the
likelihood
of
acquir-
ing
I.
pacificus
nymphs
(Lane
et
al.,
1992,
2004,
2007).
Previous
risk
assessment
studies
on
human
exposure
to
I.
pacificus
adult
ticks
in
recreational
areas
in
northwestern
California,
an
area
where
Lyme
∗Corresponding
author.
Tel.:
+1
510
412
6252;
fax:
+1
510
412
6263.
E-mail
address:
Kerry.Padgett@cdph.ca.gov
(K.A.
Padgett).
disease
is
endemic,
have
focused
on
the
behaviors
or
habitats
that
increase
exposure
to
adult
ticks
(Kramer
and
Beesley,
1993;
Lane,
1996;
Hui
et
al.,
1998;
Li
et
al.,
2000).
Although
Li
et
al.
(2000)
did
focus
on
exposure
risk
of
nymphs
within
San
Francisco
Bay
Area
parks
and
picnic
areas,
sampling
was
restricted
to
the
periphery
and
a
cross-section
of
picnic
areas;
wood
and
wooden
materials
such
as
logs,
tree
trunks,
benches,
and
picnic
tables
were
not
sampled.
This
study
was
conducted
at
Tilden
Regional
Park
(TRP),
a
large
urban
park
(>2000
acres)
located
in
the
hills
east
of
San
Francisco
Bay
in
Contra
Costa
County.
Over
one
million
visitors
per
year
visit
TRP,
which
has
20
picnic
areas,
lakes,
hiking
trails,
a
botanical
gar-
den,
a
carousel,
and
a
miniature
steam
train.
Major
vegetation
is
comprised
of
oaks
(Quercus
spp.),
Coastal
Redwoods
(Sequoia
sempervirens),
Pacific
Madrone
(Arbutus
menziesii),
Manzanita
(Arc-
tostaphylos
spp.),
and
native
and
introduced
grasses.
Common
hosts
for
I.
pacificus
include
Columbian
blacktail
deer
(Odocoileus
hemionus
columbianus),
dusky-footed
woodrat
(Neotoma
fuscipes),
and
brush
rabbit
(Sylvilagus
bachmani)
(Lane,
1996;
Peavey
et
al.,
1997).
Previous
studies
have
detected
Borrelia
burgdorferi
sensu
stricto,
B.
bissetti,
B.
miyamotoi,
and
Anaplasma
phagocytophilum
within
Ixodes
spp.
ticks
in
TRP
and
at
other
nearby
regional
parks
(Kramer
and
Beesley,
1993;
Lane,
1996;
Peavey
et
al.,
1997;
Postic
et
al.,
1998;
Hui
et
al.,
1998;
Mun
et
al.,
2006;
CDPH,
unpubl.
results).
Confirmed
human
cases
of
Lyme
disease,
human
granu-
locytic
anaplasmosis,
and
tularemia
have
recently
been
associated
with
recreational
or
occupational
exposure
to
ticks
at
TRP
(CDPH,
unpubl.
data).
The
prevalence
of
B.
burgdorferi
sensu
lato
in
questing
adult
ticks
in
TRP
is
approximately
1%
(CDPH,
unpubl.
data).
Three
1877-959X/$
–
see
front
matter.
Published by Elsevier GmbH.
doi:10.1016/j.ttbdis.2011.07.002
Author's personal copy
192 K.A.
Padgett,
D.L.
Bonilla
/
Ticks
and
Tick-borne
Diseases
2 (2011) 191–
195
common
human-biting
tick
species
are
present
in
TRP
(I.
pacifi-
cus,
Dermacentor
occidentalis,
and
D.
variabilis)
and
are
capable
of
transmitting
a
range
of
zoonotic
disease
agents
to
visitors.
Other
tick
species
present
in
this
park
that
are
primarily
animal
para-
sites
include
I.
spinipalpis,
I.
auritulus,
I.
brunneus,
and
Haemaphysalis
leporispalustris.
The
overall
objective
of
this
study
was
to
identify
activities
and
habitats
that
put
people
at
risk
of
adult
and
nymphal
tick
expo-
sure
at
picnic
areas
in
a
large
northern
California
recreational
park
where
B.
burgdorferi
has
been
documented.
Specific
goals
were
to
determine:
(1)
abundance
of
adult
and
nymphal
ticks
collected
at
picnic
sites,
(2)
abundance
of
nymphal
I.
pacificus
in
various
habi-
tats
associated
with
wood
(logs,
tree
trunks,
benches,
picnic
tables),
leaf
litter,
vegetation,
or
rock
walls;
and
(3)
prevalence
of
Borrelia
spp.
infection
in
I.
pacificus
adults
and
nymphs
collected
at
picnic
sites.
Materials
and
methods
Beginning
in
November
2006,
VBDS
staff
collected
adult
and
nymphal
ticks
from
various
sites
in
TRP
to
provide
samples
for
diagnostic
evaluation.
Abundance
and
prevalence
data
provided
background
tick
abundance
data
necessary
for
study
site
selection
(CDPH,
unpubl.
results).
Seven
heavily
used
picnic
areas
ranging
in
elevation
from
176
m
to
501
m
above
sea
level
were
selected
within
TRP
(Big
Springs,
Brook,
Carousel,
Fern,
Indian
Camp,
Island,
and
Steam
Trains).
All
picnic
areas
were
visited
on
a
single
day,
every
2
weeks
from
March
28
to
August
18,
2008,
coincident
with
the
time
of
year
when
nymphal
I.
pacificus
are
active.
Upon
arrival
at
each
picnic
area,
a
50
cm
×
60
cm
woven
cotton
blanket
was
placed
at
random
within
the
picnic
area.
A
biologist
sat
in
the
middle
of
the
blanket
and
took
notes
while
the
other
biologist
flagged
the
picnic
area
for
ticks
with
a
1-m2white
cotton
flannel
flag.
For
1/2
h,
each
picnic
area
was
flagged
around
the
perimeter
and
along
2
bisecting
linear
tran-
sects.
Habitat
flagged
included
vegetation
(shrubs,
grasses,
small
plants)
and
leaf
litter.
Habitat
type
where
ticks
were
collected
was
recorded.
All
trees
within
the
picnic
site
were
flagged
by
placing
the
flannel
flag
against
the
tree
trunk
at
a
height
of
1.5
m
several
times,
covering
the
entire
circumference
of
trunk.
Similarly,
logs
were
flagged
as
well
as
rock
walls
and
wooden
benches.
All
wooden
picnic
tables
and
benches
were
sampled
on
the
top
of
all
surfaces
as
well
as
the
ground
underneath.
The
sites
where
ticks
were
col-
lected
were
recorded;
ticks
were
collected
and
retained
separately
according
to
habitat
type.
Lastly,
before
leaving
each
picnic
area,
the
blanket
was
carefully
lifted,
placed
on
a
picnic
table,
and
checked
for
ticks.
While
picnic
areas
were
sampled
for
uniform
time
per
visit
(1/2
h),
the
amount
of
sampling
per
habitat
was
not
uniform,
precluding
statistical
analysis
of
ticks
per
unit
area
per
habitat
type.
The
seven
picnic
areas
had
perimeters
ranging
from
25.91
m
(Big
Springs)
to
209.21
m
(Fern)
(mean
=
115.65
m;
SD
=
60.39).
Each
pic-
nic
area
had
2–7
picnic
tables
(mean
=
4.4;
SD
=
2.3;
n
=
29).
Wooden
picnic
table
tops
and
their
benches
ranged
from
299
to
355
cm
long.
Table
tops
were
88–91
cm
wide
and
66–95
cm
tall.
The
attached
benches
were
28–30
cm
wide
and
26–61
cm
tall.
Carousel
and
Brook
were
the
only
2
sites
with
rock
walls.
These
walls
measured
588
cm
long
×
30
cm
wide
×
38
cm
tall
and
896
cm
long
×
30
cm
wide
×
38
cm
tall,
respectively.
Three
picnic
areas
(Carousel,
Fern,
and
Indian
Camp)
had
wooden
benches
not
associated
with
tables;
these
benches
ranged
from
242
to
197
cm
in
length,
28–38
cm
in
width,
and
46–54
cm
in
height.
At
each
picnic
area,
0–14
tree
trunks
(average
=
4.6;
SD
=
4.5;
n
=
32)
and
0–5
logs
were
flagged
(average
=
2.1;
SD
=
2.2;
n
=
15)
on
each
sample
day.
Adult
and
nymphal
Ixodes
spp.
ticks
collected
at
TRP
during
this
study
were
screened
for
Borrelia
spirochetes
using
a
direct
fluorescent
antibody
assay
(DFA)
(Persing
et
al.,
1990).
Ticks
were
identified
to
species,
life
stage,
and
sex
and
washed
with
phosphate
buffered
saline
(pH
7.4)
solution
(PBS).
Ticks
were
placed
individu-
ally
in
one
of
two
etched
wells
on
fluorescent
antibody
microslides
(Thermo
Fisher,
Waltham,
MA)
with
20
l
of
sterile
PBS
and
dis-
sected
with
forceps
and
a
scalpel.
The
tick
exoskeleton
and
a
small
drop
of
PBS
was
removed
from
the
microslide
and
placed
in
a
sep-
arate
2
mL
microcentrifuge
tube
(Eppendorf,
Hamburg,
Germany)
containing
20
l
sterile
PBS
and
preserved
at
−80 ◦C.
Forceps
and
scalpels
were
wiped
on
70%
ethanol-saturated
cotton
balls
and
flamed
between
ticks
to
prevent
cross-contamination
with
Borrelia.
Microslides
were
allowed
to
dry
and
placed
in
acetone
for
a
mini-
mum
of
10
min
to
fix.
Slides
were
either
prepared
for
DFA
or
frozen
at
−80 ◦C
until
ready
to
be
read.
To
check
for
Borrelia
on
acetone-fixed
slides,
slides
were
placed
on
moistened
paper
towels
within
a
sealed
incubation
cham-
ber.
Twenty
microliters
of
1:20
anti-Borrelia
antibody
conjugate
was
dispensed
on
each
well
(fluorescein
isothiocyanate-conjugated
anti-Borrelia
genus
antibody
KPL,
Inc.,
Gaithersburg,
MD)
and
incu-
bated
for
up
to
2
h
(Persing
et
al.,
1990).
Slides
were
rinsed
with
PBS,
and
a
drop
of
mounting
media
was
placed
on
each
spec-
imen
and
covered
with
a
glass
coverslip.
Slides
were
screened
for
spirochetes
under
a
fluorescent
microscope
(minimum
of
100
random
fields
of
view
at
400×magnification).
Positive
control
slides
were
made
using
B.
burgdorferi
cellular
antigen
(KPL,
Inc.).
Ticks
positive
for
Borrelia
spirochetes
by
DFA
were
also
tested
by
a
nested
polymerase
chain
reaction
(PCR)
that
targeted
the
16S–23S
intergenic
spacer
region
(IGS)
(Travinsky
et
al.,
2010).
In
addition,
all
DFA-positive
ticks
were
tested
by
multilocus
PCR
fol-
lowed
by
electrospray
ionization
mass
spectrometry
(PCR/ESI-MS)
by
Ibis
Biosciences
(Carlsbad,
CA).
This
technique
has
been
shown
to
resolve
Borrelia
genotypes
as
well
as
to
detect
mixtures
of
Borrelia
species
and
genotypes
(Crowder
et
al.,
2010).
The
risk
of
exposure
to
B.
burgdorferi
was
calculated
by
using
the
entomological
risk
index
(the
number
of
nymphs
collected
per
person-hour
multiplied
by
prevalence
of
ticks
infected
with
B.
burgdorferi)
(Mather
et
al.,
1996).
Results
A
total
of
1758
adult
I.
pacificus
was
collected
at
TRP
during
2006–2008.
Of
those,
11
of
814
adult
I.
pacificus
tested
(1.4%)
were
positive
for
Borrelia
spirochetes
by
DFA.
All
were
tested
by
molec-
ular
methods,
and
5
were
confirmed
by
PCR.
Four
of
these
were
identified
as
B.
miyamotoi
and
one
as
B.
burgdorferi
sensu
stricto.
In
the
7
picnic
areas,
18
adult
I.
pacificus,
32
D.
occidentalis,
and
14
D.
variabilis
were
collected
from
March
to
August.
The
mean
num-
ber
of
adult
ticks
per
picnic
site
per
day
was:
0.4
I.
pacificus
(range:
0–0.7;
SD
=
0.26),
0.4
D.
occidentalis
(range:
0–0.7;
SD
=
0.34),
and
0.2
D.
variabilis
(range:
0–0.4;
SD
=
0.12).
Adult
ticks
were
gener-
ally
collected
on
leaf
litter
and
vegetation
around
the
periphery.
Of
note,
one
adult
I.
pacificus
was
collected
from
a
tree
trunk,
2
adult
D.
variabilis
were
collected
off
wooden
picnic
tables,
and
3
adult
D.
variabilis
were
collected
from
a
rock
wall.
No
ticks
were
flagged
in
the
2
bisecting
linear
transects
covering
the
main
section
of
the
picnic
areas.
The
number
of
nymphal
I.
pacificus
collected
in
picnic
sites
peaked
in
late
April,
with
a
secondary
peak
in
early
June
(Fig.
1).
I.
pacificus
nymphs
(n
=
170)
were
collected
from
each
of
7
habitat
types
sampled:
leaf
litter
(37.9%),
vegetation
(20.1%),
logs
(19.0%),
picnic
tables
(12.1%),
tree
trunks
(8.6%),
rock
wall
(1.7%),
and
picnic
blanket
(0.6%).
(Fig.
2A)
The
highest
number
of
I.
pacificus
nymphs
was
collected
from
leaf
litter
(n
=
66),
but
when
wooden
materials
were
combined
(logs,
tree
trunks,
and
picnic
tables),
the
abundance
of
nymphs
on
wood
products
was
similar
to
that
found
in
leaf
Author's personal copy
K.A.
Padgett,
D.L.
Bonilla
/
Ticks
and
Tick-borne
Diseases
2 (2011) 191–
195 193
0
5
10
15
20
25
30
35
Mar
26
Apr
7
Apr
25
May
5
May
19
Jun
2
Jun
16
Jun
30
Jul
14
Jul
28
Aug
18
No. Nymphs Flagged
Fig.
1.
Number
of
Ixodes
pacificus
nymphs
flagged
per
collection
date,
Tilden
Regional
Park,
California,
U.S.A.,
March
to
August
2008.
litter
(Fig.
2B).
Nymphal
ticks
were
also
flagged
from
small
wooden
benches
in
picnic
areas.
The
majority
of
I.
pacificus
nymphs
was
col-
lected
from
the
Carousel
picnic
area
(n
=
82)
followed
by
the
Fern
picnic
area
(n
=
25).
The
average
number
of
I.
pacificus
nymphs
col-
lected
per
day
at
all
7
picnic
areas
for
the
sample
period
was
15.8
(0–33,
SD
=
10.8).
In
total,
nymphs
of
the
following
species
of
ticks
were
collected
from
the
7
picnic
areas:
170
I.
pacificus,
1
I.
auritulus,
2
I.
spinipalpis,
1
D.
occidentalis,
and
2
Haemaphysalis
leporispalustris
(Furman
and
Loomis,
1984).
The
2
H.
leporispalustris
nymphs
were
collected
on
a
picnic
table
and
leaf
litter;
the
single
D.
occidentalis
nymph
was
collected
on
surrounding
vegetation.
Five
of
170
(2.9%)
I.
pacificus
nymphs
tested
positive
for
Borre-
lia
spirochetes
by
DFA.
Borrelia-positive
I.
pacificus
nymphs
were
detected
on
a
picnic
table
(n
=
1),
a
log
(n
=
1),
and
from
picnic
area
leaf
litter
or
directly
under
picnic
tables
(n
=
3).
These
positive
ticks
were
collected
at
the
2
sites
with
the
highest
abundance
of
nymphal
I.
pacificus:
Carousel
picnic
area
(n
=
3)
and
at
Fern
picnic
area
(n
=
2).
Three
of
these
ticks
(1.8%)
were
positive
for
B.
burgdorferi
sensu
stricto
by
PCR.
Of
these,
2
were
tested
by
PCR/ESI-MS
and
were
genotyped
as
either
genotype
3
or
43;
both
were
nymphs
collected
in
leaf
litter
at
Carousel
picnic
area
(Crowder
et
al.,
2010).
The
other
2
DFA-positive
I.
pacificus
nymphs
were
either
negative
by
molecular
tests
or
had
too
little
DNA
in
the
sample
to
confirm
with
confidence.
A
single
female
I.
auritulus
collected
from
a
rock
wall
at
the
Carousel
picnic
area
tested
positive
for
Borrelia
spp.
by
DFA,
nested
PCR,
and
PCR/ESI-MI.
Sequencing
of
the
16S
rRNA
gene,
using
primers
designed
by
Ibis
Biosciences,
revealed
a
mixture
of
2
Borre-
lia
species
in
different
amounts;
the
main
sequence
was
B.
bissettii
BankIt1450655
Seq1
JF911485
and
the
minor
sequence
B.
burgdor-
feri
BankIt1450655
Seq2
JF911486.
0
10
20
30
40
50
60
70
Picnic
Tables
Tree
Trunks
Downed
Logs
Vegetation Leaf Litter Rock Wall Picnic
Blanket
No. Ticks
A
B
0
10
20
30
40
50
60
70
80
Wood
Products*
Vegetation
Leaf Litter
Rock Wall
Picnic
Blanket
No. Ticks
Fig.
2.
(A)
Ixodes
pacificus
nymphs
collected
in
Tilden
Regional
Park,
California,
U.S.A.,
picnic
habitats,
2008.
(B)
*Wood
products
include
wooden
picnic
tables,
logs,
and
tree
trunks.
Human
risk
assessment
in
picnic
areas
The
risk
of
exposure
to
nymphal
I.
pacificus
was
moderate,
with
a
risk
of
exposure
to
approximately
4.5
nymphs
per
hour
of
activity
at
a
picnic
site.
The
risk
of
exposure
to
Borrelia
spirochetes,
including
B.
burgdorferi,
at
the
picnic
sites
was
low
overall
with
an
entomo-
logical
risk
index
calculated
at
13.1
(4.5
ticks
per
hour
multiplied
by
2.9%
prevalence).
When
analyzed
per
picnic
area,
the
only
pic-
nic
areas
with
positive
ticks
and
detectable
entomological
risk
were
Carousel
and
Fern
(Table
1).
Discussion
This
is
the
first
study
to
demonstrate
a
potential
risk
of
tick-
borne
disease
exposure,
primarily
for
Lyme
disease,
from
sitting
on
wooden
picnic
tables
in
spring
and
summer.
Previous
studies
have
demonstrated
that
human
behaviors
that
involve
contact
with
wood
or
wood
products
put
people
at
risk
of
acquiring
nymphal
Table
1
Risk
of
exposure
to
Borrelia
spirochetes
in
Ixodes
pacificus
Tilden
Regional
Park
picnic
areas
California,
U.S.A.,
2008.
Picnic
area
Number
of
visits
Nymphs
collected
Nymphs/hour
Prevalence
ERI*
Steam
Trains
11
13
2.4
0
0
Big
Springs
10
16
3.2
0
0
Island
11
8
1.5
0
0
Brook
11
16
2.9
0
0
Carousel
11
82
14.9
3.7
55.1
Fern 11
25
4.6
8.0
36.8
Indian
Camp
11
10
1.8
0
0
*ERI,
entomologic
risk
index
=
nymphs/hour
multiplied
by
prevalence
of
Borrelia
spirochetes.
Author's personal copy
194 K.A.
Padgett,
D.L.
Bonilla
/
Ticks
and
Tick-borne
Diseases
2 (2011) 191–
195
I.
pacificus
and
risk
exposure
to
the
diseases
they
may
transmit
(Lane
et
al.,
1992,
2004,
2007).
Although
wooden
logs
and
tree
trunks
were
investigated
previously
for
tick
exposure
risk,
no
study
has
focused
specifically
on
recreational
activities
that
incorporate
wooden
materials
such
as
the
risk
of
tick
exposure
from
sitting
on
picnic
tables
and
wooden
benches.
The
public
are
more
likely
to
spend
time
sitting
at
picnic
tables,
wooden
benches,
and
logs
than
they
would
sitting
in
leaf
litter,
therefore
raising
the
likelihood
of
acquiring
ticks
from
these
wooden
substrates.
In
TRP,
nymphal
I.
pacificus
were
collected
from
March
through
the
end
of
July
with
the
peak
of
abundance
late
April
and
a
sec-
ondary
peak
in
early
June.
It
is
likely
nymphs
are
active
prior
to
our
sampling,
perhaps
as
early
as
late
January
(Bonilla,
unpubl.
results),
but
as
January
and
February
are
months
of
high
rainfall
in
Califor-
nia,
these
months
are
difficult
to
sample
for
nymphs.
This
time
of
year
when
nymphs
are
present
in
picnic
areas
coincides
with
the
time
of
year
when
picnic
areas
are
most
heavily
used
(spring
and
summer).
There
appears
to
be
low
risk
of
exposure
to
nymphal
or
adult
ticks
in
August
and
the
fall
in
TRP,
although
in
nearby
Men-
docino
County,
nymphal
ticks
are
abundant
through
August
(Eisen
et
al.,
2002).
Adult
I.
pacificus
become
active
again
in
late
fall
and
early
winter
(Kramer
and
Beesley,
1993;
Lane,
1996).
In
this
study,
ticks
were
screened
for
Borrelia
spirochetes
by
DFA,
and
further
testing
consisted
of
PCR
or
PCR/ESI-MS
to
identify
species
or
genotype.
The
use
of
DFA
by
experts
has
been
shown
to
be
as
sensitive
as
molecular
methods,
but
is
not
as
specific
(Persing
et
al.,
1990);
therefore,
it
is
helpful
to
include
additional
molecu-
lar
tests
for
specific
identification
of
positive
samples.
For
example,
the
use
of
PCR/ESI-MS
is
able
to
indicate
that
one
of
two
B.
burgdor-
feri
s.s.
genotypes
from
TRP
nymphs
belongs
to
a
genotype
(43)
described
from
nymphs
in
Suffolk
County
New
York,
and
other
TRP
nymphs
harbored
genotype
3,
previously
described
from
ticks
in
Sonoma
County.
In
this
study,
4
I.
pacificus
adult
ticks
from
TRP
were
found
infected
with
B.
miyamotoi,
but
this
spirochete
was
not
detected
in
any
nymphs.
B.
miyamotoi
has
been
detected
in
Califor-
nian
I.
pacificus
in
the
past
and
is
not
known
to
be
pathogenic
to
humans
(VBDS
Annual
Report,
2003;
Mun
et
al.,
2006).
Other
species
of
Ixodes
from
TRP
were
tested
for
Borrelia
spp.
Three
of
25
(12.0%)
I.
spinipalpis
collected
in
2007
and
2008
at
TRP
picnic
sites
were
positive
for
B.
burgdorferi
sensu
lato.
Posi-
tive
I.
spinipalpis
were
collected
from
leaf
litter
in
areas
with
many
dusky-footed
woodrat
nests
(CDPH,
unpubl.
results).
In
addition
to
B.
burgdorferi,
I.
spinipalpis
from
TRP
have
been
shown
to
harbor
B.
bissettii
(Postic
et
al.,
1998).
In
this
study,
I.
auritulus,
an
Ixodes
species
that
feeds
primarily
on
birds,
was
found
to
harbor
a
mixture
of
B.
burgdorferi
and
B.
bissettii.
B.
burgdorferi
s.l.,
with
genetic
char-
acteristics
similar
to
B.
bissettii,
was
recently
detected
in
I.
auritulus
removed
from
Canadian
birds
(Morshed
et
al.,
2005;
Scott
et
al.,
2010).
Recent
detection
of
B.
bissettii
in
sera
from
some
Lyme
dis-
ease
patients
in
north-coastal
California
has
enhanced
interest
in
B.
bissettii
as
a
potential
human
pathogen
in
California
(Girard
et
al.,
2010).
The
risk
of
acquiring
a
nymphal
tick
while
spending
time
in
TRP
picnic
areas
is
moderate
during
spring
and
summer
and
lower
than
in
mid-west
(Paskewitz
et
al.,
2001)
and
east
coast
(Mather
et
al.,
1996)
study
sites.
The
ERI,
number
of
infected
nymphs
encountered
per
hour,
was
low
overall
in
TRP,
but
slightly
higher
in
those
2
picnic
sites
with
higher
tick
numbers
and
with
positive
ticks
(Carousel
and
Fern).
These
2
picnic
areas
were
adjacent
to
each
other
and
were
similar
in
plant
composition
to
other
picnic
areas
sampled.
It
is
not
clear
why
these
2
areas
had
higher
tick
numbers.
Sites
with
high
nymphal
tick
abundance
based
either
on
ticks
collected
per
unit
time
or
per
distance,
and/or
high
infection
prevalence
with
B.
burgdorferi
have
elevated
ERI
and
have
been
associated
with
higher
numbers
of
Lyme
disease
cases
(Mather
et
al.,
1996).
In
this
study,
risk
of
exposure
to
nymphal
ticks
in
picnic
areas
is
apt
to
be
highly
variable
according
to
time
and
amount
of
contact
an
individual
has
with
wood
and
leaf
litter
on
any
given
occasion.
Public
health
recommendations
for
recreational
areas
where
Lyme
disease
has
been
well
documented
should
include
check-
ing
for
ticks
after
visiting
picnic
areas
and
sitting
at
wooden
picnic
tables
in
parks
where
ticks
have
been
shown
to
be
present.
While
this
study
was
implemented
in
only
one
park
where
tick-borne
B.
burgdorferi
has
been
well-documented,
additional
studies
at
other
parks
and
recreational
areas
with
documented
B.
burgdorferi
may
further
document
this
potential
risk.
It
is
likely
that
results
from
this
study
are
applicable
to
other
regions/recreational
areas
of
Cal-
ifornia
where
land
use
and
management
are
geared
to
providing
opportunities
for
the
public
to
access
nature.
Acknowledgements
We
are
grateful
for
excellent
field
assistance
from
Anne
Kjemtrup,
Stan
Husted,
Laurel
Ormiston,
and
Tina
Feiszli
(CDPH).
Thanks
also
to
Mark
Eshoo,
Chris
Crowder,
and
Heather
Matthews
of
Ibis
Biosciences
and
Inger
Vilcins
(CDPH)
for
molecular
testing
of
DFA-positive
samples
using
PCR
as
well
as
the
Ibis
Biosciences
T5000
system.
We
also
thank
Nancy
Brownfield
(East
Bay
Regional
Parks)
and
Vicki
Kramer
(CDPH)
for
support
of
this
study.
References
Clover,
J.R.,
Lane,
R.S.,
1995.
Evidence
implicating
nymphal
Ixodes
pacificus
(Acari:
Ixodidae)
in
the
epidemiology
of
Lyme
disease
in
California.
Am.
J.
Trop.
Med.
Hyg.
53,
237–240.
Crowder,
C.D.,
Matthews,
H.E.,
Schutzer,
S.,
Rounds,
M.A.,
Luft,
B.J.,
Nolte,
O.,
Campbell,
S.R.,
Phillipson,
C.A.,
Li,
F.,
Sampath,
R.,
Ecker,
D.J.,
Eschoo,
M.W.,
2010.
Genotypic
variation
and
mixtures
of
Lyme
Borrelia
in
Ixodes
ticks
from
North
America
and
Europe.
PLoS
ONE
5,
e10650,
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010650.
Eisen,
L.,
Eisen,
R.,
Eisen,
R.J.,
Lane,
R.S.,
2002.
Seasonal
activity
patterns
of
Ixodes
paci-
ficus
nymphs
in
relation
to
climatic
conditions.
Med.
Vet.
Entomol.
16,
235–244.
Furman,
D.P.,
Loomis,
E.C.,
1984.
The
Ticks
of
California
(Acari:
Ixodida).
Bulletin
of
the
California
Insect
Survey,
vol.
25.
University
of
California
Press.
Girard,
Y.A.,
Fedorova,
N.,
Lane,
R.S.,
2010.
Genetic
diversity
of
Borrelia
burgdor-
feri
and
detection
of
B.
bissettii-like
DNA
in
serum
of
north-coastal
California
residents.
J.
Clin.
Microbiol.
49,
945–954.
Hui,
L.T.,
Pontiflet,
E.,
Scott,
H.A.,
1998.
Habitat
and
seasonal
abundance
of
ticks
in
urban
recreation
areas
of
Alameda
County,
California.
Proc.
Mosq.
Vector
Cont.
Assoc.
66,
56–66.
Kramer,
V.L.,
Beesley,
C.,
1993.
Temporal
and
spatial
distribution
of
Ixodes
pacifi-
cus
and
Dermacentor
occidentalis
(Acari:
Ixodidae)
and
prevalence
of
Borrelia
burgdorferi
in
Contra
Costa
County,
California.
J.
Med.
Entomol.
30,
549–554.
Lane,
R.S.,
Manweiler,
S.A.,
Stubbs,
H.A.,
Lennette,
E.T.,
Madigan,
J.E.,
Lavoie,
P.E.,
1992.
Risk
factors
for
Lyme
disease
in
a
small
rural
community
in
Northern
California.
Am.
J.
Epidemiol.
136,
1358–1368.
Lane,
R.S.,
1996.
Risk
of
human
exposure
to
vector
ticks
(Acari:
Ixodidae)
in
a
heavily
used
recreational
area
in
Northern
California.
Am.
J.
Epidemiol.
55,
165–173.
Lane,
R.S.,
Steinlein,
D.B.,
Mun,
J.,
2004.
Human
behaviors
elevating
exposure
to
Ixodes
pacificus
(Acari:
Ixodidae)
nymphs
and
their
associated
bacterial
zoonotic
agents
in
a
hardwood
forest.
J.
Med.
Entomol.
41,
239–248.
Lane,
R.S.,
Mun,
J.,
Peribanez,
M.A.,
Stubbs,
H.,
2007.
Host-seeking
behavior
of
Ixodes
pacificus
(Acari:
Ixodidae)
nymphs
in
relation
to
environmental
parameters
in
dense-woodland
and
woodland-grass
habitats.
J.
Vector
Ecol.
32,
342–357.
Li,
X.,
Peavey,
C.A.,
Lane,
R.S.,
2000.
Density
and
spatial
distribution
of
Ixodes
pacificus
(Acari:
Ixodidae)
in
two
recreational
areas
in
north
coastal
California.
Am.
J.
Trop.
Med.
Hyg.
62,
415–422.
Mather,
T.N.,
Nicholson,
M.C.,
Donnelly,
E.F.,
Matyas,
B.T.,
1996.
Entomological
index
for
human
risk
of
Lyme
disease.
Am.
J.
Epidemiol.
144,
1066–1069.
Morshed,
M.G.,
Scott,
J.D.,
Fernando,
K.,
Beati,
L.,
Mazerolle,
D.F.,
Geddes,
G.,
Durden,
L.A.,
2005.
Migratory
songbirds
disperse
ticks
across
Canada,
and
first
isolation
of
the
Lyme
disease
spirochete,
Borrelia
burdgorferi,
from
the
avian
tick,
Ixodes
auritulus.
J.
Parasitol.
91,
780–790.
Mun,
J.,
Eisen,
R.J.,
Eisen,
L.,
Lane,
R.S.,
2006.
Detection
of
a
Borrelia
miyamotoi
sensu
lato
relapsing-fever
group
spirochete
from
Ixodes
pacificus
in
California.
J.
Med.
Entomol.
43,
120–123.
Paskewitz,
S.M.,
Vandermause,
M.,
Belongia,
E.A.,
Kazmierczak,
J.J.,
2001.
Ixodes
scapularis
(Acari:
Ixodidae):
abundance
and
rate
of
infection
with
Borrelia
burgdorferi
in
four
state
parks
in
Wisconsin.
J.
Med.
Entomol.
38,
33–38.
Peavey,
C.A.,
Lane,
R.S.,
Kleinjan,
J.E.,
1997.
Role
of
small
mammals
in
the
ecology
of
Borrelia
burgdorferi
in
a
peri-urban
park
in
north
coastal
California.
Exp.
Appl.
Acarol.
21,
569–584.
Author's personal copy
K.A.
Padgett,
D.L.
Bonilla
/
Ticks
and
Tick-borne
Diseases
2 (2011) 191–
195 195
Persing,
D.H.,
Telford,
S.R.,
Spielman,
A.,
Barthold,
S.W.,
1990.
Detection
of
Borrelia
burgdorferi
infection
in
Ixodes
dammini
ticks
with
the
polymerase
chain
reaction.
J.
Clin.
Microbiol.
28,
566–572.
Postic,
D.,
Ras,
N.M.,
Lane,
R.S.,
Hendson,
M.,
Baranton,
G.,
1998.
Expanded
diversity
among
Californian
Borrelia
isolates
and
description
of
Borrelia
bis-
settii
sp.
nov.
(formerly
Borrelia
group
DN127).
J.
Clin.
Microbiol.
36,
3497–
3504.
Scott,
J.D.,
Lee,
M.-K.,
Fernando,
K.,
Durden,
L.A.,
Jorgensen,
D.R.,
Mak,
S.,
Mor-
shed,
M.G.,
2010.
Detection
of
Lyme
disease
spirochete,
Borrelia
burgdorferi
sensu
lato
including
three
novel
genotypes
in
ticks
(Acari:
Ixodidae)
col-
lected
from
songbirds
(Passeriformes)
across
Canada.
J.
Vect.
Ecol.
35,
124–
139.
Travinsky,
B.,
Bunikis,
J.,
Barbour,
A.G.,
2010.
Geographic
differences
in
genetic
locus
likages
for
Borrelia
burgdorferi.
Emerg.
Inf.
Dis.
16,
1147–1150.
Vector-Borne
Disease
Section,
California
Department
of
Public
Health,
2003.
Annual
Report.
http://www.cdph.ca.gov/programs/
vbds/Pages/VBDSAnnualReports.aspx.
