Vet. Res. 35 (2004) 585–595
© INRA, EDP Sciences, 2004
Bartonella henselae IgG antibodies are prevalent
in dogs from southeastern USA
Laia SOLANO-GALLEGO, Julie BRADLEY, Barbara HEGARTY,
Betsy SIGMON, Edward BREITSCHWERDT*
Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University
(NCSU), 4700 Hillsborough Street, Raleigh, NC 27606, USA
(Received 2 February 2004; accepted 30 March 2004)
Abstract – In contrast to the large body of literature regarding Bartonella henselae in humans and
cats, there is little information about B. henselae as an infectious agent in dogs. Due to the paucity
of information regarding the B. henselae serology in dogs, we performed a cross-sectional
serosurvey using B. henselae antigen in order to compare the seroprevalence between sick and
healthy dogs from the south-eastern USA. Ninety-nine sera were collected from clinically healthy
dogs. Three hundred and one sera from sick dogs were submitted to North Carolina State University
for serologic screening against a panel of arthropod-transmitted organisms. Serological tests were
performed using B. henselae (Bh), Rickettsia rickettsii (Rr), Ehrlichia canis (Ec), Bartonella
vinsonii subspecies berkhoffii (Bvb), Babesia canis (Bc) and Borrelia burgdorferi (Bb) antigens.
Serum B. henselae IgG antibodies were detected in 10.1% of healthy dogs and in 27.2% of sick
dogs. The difference in seroprevalence between the two groups was statistically significant. The
majority of seroreactive dogs (80%) had low titers of 1:64 or 1:128. In healthy dogs, seroprevalence
for Rr was 14.1% and for Bvb was 1%. In sick dogs, Rr seroprevalence was 29.7%, Ec 6.5%, Bvb
4.7%, Bb 1.7% and Bc was 0.85%. Of the sick dogs that were seroreactive to B. henselae antigens,
40.6% were also seroreactive to Rr, 15.0% reactive to Bvb antigens, 14.8% reactive to Ec antigens,
1.8% reactive to Bc antigens and 1.75% reactive to Bb antigens. Sera from dogs experimentally
infected with B. vinsonii subsp. berkhoffii, E. canis or R. rickettsii did not cross react with B.
henselae antigens, by IFA testing. This study indicates that B. henselae IgG antibodies are prevalent
in healthy and sick dogs living in the south-eastern USA. Nevertheless, further studies are needed
to evaluate the epidemiological, clinical and zoonotic relevance of B. henselae infection in dogs.
Bartonella henselae / dog / serology / vector-borne diseases
Members of the genus Bartonella are ple-
omorphic, gram-negative rods that are highly
adapted to facilitate intracellular persist-
ence in a wide variety of animals . Bar-
tonella organisms can induce clinical dis-
ease in humans  and in other mammals
such as the domestic cat and dog . One
of the most important Bartonella species
that causes a broad spectrum of clinical con-
ditions in humans is Bartonella henselae
* Corresponding author: firstname.lastname@example.org
586L. Solano-Gallego et al.
. In immunocompetent patients, cat
scratch disease (CSD) caused by B. hense-
lae is mainly characterized by a benign
regional lympadenopathy, while a low pro-
portion of CSD patients may develop atyp-
ical manifestations [12, 48]. Bartonella hense-
lae is also a frequent cause of prolonged
fever in children [33, 62]. In immunocom-
promised patients, bacillary angiomatosis
 and bacillary peliosis hepatis or splen-
itis are the most common B. henselae- induced
disease manifestations . In people, the
major risk factor associated with B. hense-
lae infection is cat exposure, especially cat
scratches [14, 64].
The cat flea (Ctenocephalides felis) is
the main arthropod  vector of B. hense-
lae and cats serve as the main vertebrate res-
ervoir . The most probable route for cat
to cat transmission of B. henselae is via intra-
dermal inoculation of infected feces from
cat fleas [21, 22]. Several studies have found
high seroprevalences in cats worldwide,
ranging from 1%  to 81%  depending
on the climate and presumably flea density
of each geographical region studied. Sero-
prevalences of B. henselae antigens are much
greater in cats that live in warm, humid
regions of the world where flea infestation
is expected . The prevalence of bacter-
emia documented in different countries,
although variable, is often high and ranges
from 9%  to 90% , depending upon
the study location and the cat population
Although the prevalence of B. henselae
infection can be high in apparently healthy
cats, several studies suggest that cats may
suffer clinicopathological consequences due
to persistent B. henselae infection .
Cats experimentally infected with B. hense-
lae developed various clinical signs such as
fever, lethargy, transient anemia, lymphad-
enomegaly, neurological dysfunction, repro-
ductive failure [28, 29, 39, 53]. Pathological
abnormalities in experimentally infected
cats included lymph node and splenic hyper-
plasia, splenic microabcesses, lymphocytic
plasmacytic myocarditis, focal pyogranulo-
matous nephritis, lymphocytic interstitial
nephritis and lymphocytic cholangiohepa-
titis [28, 39, 41]. Less information is avail-
able on clinical disease in naturally infected
cats. However, based on serological stud-
ies, naturally infected cats are more likely
to develop lymphadenitis, gingivitis, sto-
matitis and are predisposed to urological
diseases [25, 63]. Additionally, uveitis asso-
ciated with detection of B. henselae DNA
and antibodies in aqueous humor has been
reported in cats .
Since the isolation and characterization
of B. henselae in 1992 , a large body of
literature has been generated regarding bar-
tonellosis in humans and cats. However,
there is little information about B. henselae
infection in dogs. Historically, dogs have
been infrequently implicated in the trans-
mission of B. henselae to humans [36, 61].
Recently, B. henselae DNA has been ampli-
fied and sequenced from the liver of a dog
with peliosis hepatitis  and a dog with
granulomatous hepatitis  and from the
blood of three dogs with either fever, throm-
bocytopenia or neurologic dysfunction .
Three canine serosurveys carried out in
Hawaii, Japan and the United Kingdom
describe B. henselae seroprevalence of 6.5%
, 7.7%  and 3% , respectively. In
Japan, B. henselae PCR positive results were
also reported from peripheral blood, nail
clippings and oral swabs in 15% of the dogs
studied . To further characterize B. hense-
lae seroprevalence in dogs, we performed a
survey in a population of healthy and sick
dogs from the south-eastern USA. To com-
pare B. henselae seroprevalence with expo-
sure to other vector-borne diseases, sera
were also tested for Rickettsia rickettsii,
Ehrlichia canis, Bartonella vinsonii subsp.
berkhoffii, Babesia canis and Borrelia burg-
dorferi IgG antibodies in the same popula-
tion of dogs.
B. henselae IgG antibodies in dogs 587
2. MATERIALS AND METHODS
Ninety-nine sera were collected between
October 2002 and February 2003 at a pri-
vate veterinary hospital located in Cary (North
Carolina, USA). These sera represent a con-
venience sample of clinically healthy dogs
that were screened for Dirofilaria immitis
antigen, E. canis antibodies (P30 and P31
outer membrane proteins) and B. burgdor-
feri (C6 peptide) with a commercial assay
kit (Canine SNAP® 3Dx™ Test; IDEXX
Laboratories, USA). Only sera from those
dogs with normal physical examination find-
ings and negative 3Dx test results were
included in this study. Sixty-eight of the
healthy dogs were females (67 spayed, 1 intact)
and 31 dogs were male (25 neutered, 6 intact).
The age was known for 95 dogs with a mean
± standard deviation of 5.1 ± 2.9 years. Ages
ranged from 9 months to 13 years. Various
breeds were represented and 11 dogs were
mixed breed. Seventy-four dogs were treated
with tick/flea control products. The tick/
flea control status was unknown in 21 dogs
and 4 dogs did not receive any tick/flea con-
trol treatment. The sera were tested by immun-
ofluorescence assay (IFA) to determine B.
henselae seroprevalence in a population of
healthy dogs, with limited exposure to ticks
and fleas. Sera from these dogs were also
tested for B. canis, B. vinsonii subsp. berkhof-
fii, and R. rickettsii IgG antibodies by IFA.
Three hundred and one sera from sick
dogs living in the southeastern USA (252
sera from North Carolina) that were submit-
ted to the NCSU-Vector Borne Disease
Diagnostic Laboratory for serologic screen-
ing for arthropod-transmitted diseases from
October 2000 to April 2003 were also included
in this study. Clinicopathological findings
of sick dogs compatible with arthropod-trans-
mitted diseases were categorized in neuro-
logical, ocular, cardiac, hematological, ortho-
pedic or multisystemic disorders. Several
purebred and mixed breed dogs were rep-
resented in the study population, but age,
breed and sex was not provided for these
diagnostic accessions. Sera from sick dogs
were tested for IgG antibodies to B. hense-
lae (n = 301), to B. vinsonii subsp. berkhof-
fii (n = 295), to R. rickettsii (n = 232), to E.
canis (n = 231), to B. canis (n = 233) by an
in house IFA and to B. burgdorferi (n = 230)
using the Canine SNAP® 3Dx™ Test .
2.2.1. Detection of IgG antibodies
to B. henselae, B. vinsonii subsp.
berkhoffii, R. rickettsii, E. canis
and B. canis
Bartonella henselae , B. vinsonii subsp.
berkhoffii NCSU 93CO1  and R. rick-
ettsii NCSU Domino strain  were culti-
vated in Vero cells and harvested when cells
were more than 80% infected (2 to 9 days
postinoculation). Ehrlichia canis (Florida
strain) was grown as described previously
by in vitro propagation in 030 cell line cul-
ture . Antigen for IFA was prepared by
pelleting and re-suspending microorgan-
isms and cells in phosphate buffered saline
(PBS). Babesia canis antigen slides were
made from the blood of dogs experimen-
tally inoculated with these piroplasms as
previously described . Antigens were
applied to 30-well Teflon-coated slides (Cel-
line Associates, Newfield, NJ, USA) in 3.0 µL
aliquots and air-dried. Slides were fixed in
acetone for 10 min and frozen at –20 °C until
Three twofold serial dilutions of sera
(1:16, 1:32, 1:64) in PBS 0.05% Tween 20
(T)-0.5% dried skim milk (M)-1% goat sera
(G) were made in microtiter plates. Ten
microliters of each dilution was applied per
well, and slides were incubated at 37 °C for
30 min, washed in PBS with agitation for
30 min and air-dried. Fluorescein conju-
gated goat anti-dog immunoglobulin (whole
molecule immunoglobulin G; Cappel, Orga-
non Teknika Corp., Durham, NC, USA)
was diluted 1:100 in PBSTMG, filtered
with 0.22 µm filter to remove precipitants
and applied to each well. Slides were incu-
bated for 30 min at 37 °C and washed again
588L. Solano-Gallego et al.
in PBST with agitation for 30 min, rinsed
with deionized water, air dried, cover slipped
using mounting medium (90% glycerol and
10% PBS, pH 9.0) and viewed with a fluo-
rescence microscope (magnification, ×40).
Ehrlichia canis IFA was performed on each
serum sample as described above; the only
modification was that slides, after the last
wash with PBST, were counter stained with
Eriochrome black before the final rinse in
deionized water. Samples with an IFA titer
> 1:32 were retested with serial dilutions
from 1:16 to 1:8192. End-point titers were
determined as the last dilution at which
brightly stained organisms could be detected
on a fluorescence microscope with exciter
and barrier filters using a 50 watt light source.
For all antigens, a reactive serum was
defined as a titer of ≥ 1:64. Sera from dogs
experimentally infected with B. henselae
(titer 1:512) (kindly provided by Dr Bruno
Chomel, University of California, Davis,
USA, unpublished results), B. vinsonii subsp.
berkhoffii (titer 1:1024), R. rickettsii (titer
1:2048), E. canis (titer 1:4096) and B. canis
(1:1024) were used as positive controls,
while a nonreactive serum from a specific
pathogen free (SPF) dog was used as a neg-
ative control for all IFA testing.
Sera from dogs experimentally-infected
with R. rickettsii, E. canis or B. vinsonii subsp.
berkhoffii were tested by B. henselae IFA to
determine if there was crossreactivity among
these organisms. These dogs were seroneg-
ative to respective antigens prior to the exper-
imental infection. The median geometric R.
rickettsii titer for six experimentally infected
dogs was 1:512 at 21 days postinfection .
The median geometric E. canis titer for seven
experimentally infected dogs was 1:1722 at
49 days postinfection . The median
geometric titer of nine dogs experimentally
infected with B. vinsonii subsp. berkhoffii
was 1:1755 at 31 days postinfection .
2.3. Statistical analysis
Chi-square was used to test for associa-
tions between groups. Differences were
considered significant if the P-value was
The results of B. henselae, R. rickettsii,
E. canis, B. vinsonii subsp. berkhoffii, B.
burgdorferi, B. canis seroprevalences in
healthy and sick dogs are shown in Table I.
The differences in B. henselae and R. rick-
ettsii seroprevalences between the healthy
and sick dog populations were statistically
significant (Chi-square = 12.36, P = 0.00043;
Chi-square = 8.99, P = 0.0027; respectively).
The difference in B. vinsonii subsp. berkhoffii
Table I. Seroprevalences of different arthropod-transmitted organisms in clinically healthy and sick
Arthropod-transmitted organismsHealthy dogs*Sick dogs*All dogs*
B. vinsonii subsp. berkhoffii
* Number of seroreactive dogs/total number of dogs (% of seroreactive dogs).
n.d.: not determined with the same technique.
B. henselae IgG antibodies in dogs 589
seroprevalence between the two groups
was not statistically significant (Chi-square =
2.765, P = 0.096; Yates’ Chi-square = 1.897,
P = 0.168).
In clinically healthy dogs, six dogs had
a B. henselae titer of 1:64, three dogs 1:128
and one dog 1:256, with a geometric median
titer of 1:90. Rickettsia rickettsii titers
ranged from 1:64 to 1:2048 with a geomet-
ric median titer of 1:210. The only dog sero-
reactive to B. vinsonii subsp. berkhoffii anti-
gens had a titer of 1:64. None of the healthy
dogs that were seroreactive to R. rickettsii
or B. vinsonii subsp. berkhoffii antigens
were seroreactive to B. henselae antigens.
In sick dogs, B. henselae positive titers
ranged from 1:64 to 1:4096 with a geomet-
ric median titer of 1:118; however, the
majority of seroreactive dogs (80.4%, 66 of
82) had low titers (1:64 or 1:128) (Fig. 1).
Rickettsia rickettsii titers ranged from 1:64
to 1:2048 with a geometric median titer of
1:146. Ehrlichia canis titers ranged from
1:64 to 1:4096 with a geometric median titer
of 1:308. Bartonella vinsonii subsp. berkhof-
fii titers ranged from 1:64 to 1:512 with a
geometric median titer of 1:136. Babesia
canis titers were 1:64.
The presence of serum B. henselae anti-
bodies was not associated with seroreactiv-
ity to B. burgdorferi or B. canis antigens. In
contrast, of the samples that were reactive
with R. rickettsii, E. canis and B. vinsonii
subsp. berkhoffii antigens, 34%, 53% and
85% (P = 0.035, P = 0.011 and P = 0.0000029;
respectively) were seroreactive to B. hense-
lae antigens (Tab. II).
The presence of E. canis or R. rickettsii
antibodies was not associated with serore-
activity to B. vinsonii subsp. berkhoffii anti-
gens. In contrast, the detection of E. canis
antibodies was associated with seroreactiv-
ity to R. rickettsii antigens (Chi-square =
14.28, P = 0.00015; Yates’ Chi-Square =
12.16, P = 0.00048).
Table III summarizes the results of sera
that were reactive to both B. vinsonii subsp.
berkhoffii and B. henselae antigens. Six out
of 12 dogs had a higher B. henselae titer
Figure 1. Frequency of B. henselae seroreactive titers in healthy and sick dogs from the southeast
region of USA.
590L. Solano-Gallego et al.
than B. vinsonii subsp. berkhoffii titer. Four
out of 12 dogs had the same titer to both
organisms and two out of 12 dogs had a
higher titer to B. vinsonii subsp. berkhoffii
antigens than for B. henselae antigens.
Sera from the dogs experimentally
infected with R. rickettsii or E. canis were
not seroreactive to B. henselae antigens (all
B. henselae titers were less than 1:16). One
out of nine sera from the dogs experimen-
tally infected with B. vinsonii subsp.
berkhoffii was reactive to B. henselae anti-
gens with a titer of 1:64, two dogs had titers
of 1:32 and one dog had a titer of 1:16. Bar-
tonella henselae antibodies were not detect-
able in the remaining 5 samples (titers were
less than the 1:16 screening dilution).
This study indicates that B. henselae IgG
antibodies are prevalent in healthy and sick
dogs living in the southeastern USA. The
total B. henselae seroprevalence (23.5%) is
greater than previous serosurveys, that
described a B. henselae seroprevalence of
6.5% in Hawaii , 7.7% in Japan  and
3% in the United Kingdom . The differ-
ences between seroprevalences could be
explained by several factors such as differ-
ences in IFA technique, differences in the
dog populations sampled, differences in cli-
mate, the timing of sample collection, or
differences in the mode or modes of trans-
mission among the different geographic
Cat to cat transmission of B. henselae
occurs via intradermal inoculation of infected
flea feces . Transmission of B. henselae
from cats to people occurs most frequently
via cat scratches, presumably contaminated
with flea excrement . Our hypothesis is
that the transmission of B. henselae to dogs
occurs via flea excrements, ticks and scratches.
Table II. Measure of association between Bartonella henselae seroreactivity and Rickettsia rickettsii,
Ehrlichia canis, and Bartonella vinsonii subspecies berkhoffii, but not Borrelia burgdorferi or
Babesia canis seroreactivity in sick dogs from the south-eastern USA.
(IFA or C6 peptide)
R. rickettsiiE. canis B. vinsonii
B. burgdorferiB. canis
– 45 1287 1702 2133 1701 177
a Chi-square = 4.418; P = 0.035.
b Chi-square = 8.037; P = 0.0045; Yates’ chi-square = 6.348; P = 0.011.
c Chi-square = 25.5; P = 4.4e-7; Yates’ chi-square = 22.5; P = 0.00000209.
d Chi-square = 0; P = 1; Yates’ chi-square = 0.329; P = 0.566.
e Chi-square = 0.779; P = 0.377; Yates’ chi-square = 0.002; P = 0.96.
Table III. Comparative IFA titers to B. henselae
and B. vinsonii subsp. berkhoffii (Bvb) antigens
among 12 dogs seroreactive to both antigens.
Dog ID IFA titers
for B. henselae
B. henselae IgG antibodies in dogs 591
Self-inoculation with flea excrement may
result in direct transmission to a flea-infested
dog. Dogs and cats are commonly infested
with the same flea (Ctenophalides felis)
 that is known to transmit B. henselae
from infected to SPF cats . Both C. felis
from cats and dogs and C. canis from dogs
were reported to be positive for B. henselae
DNA . Recently, DNA from several Bar-
tonella spp., including B. henselae DNA,
was detected by PCR in questing Ixodes
pacificus ticks in California  and in Ixo-
des ricinus removed from people in Italy
. Consequently, vectors, such as fleas
and ticks, may be implicated in B. henselae
transmission to dogs. It is also possible that
cats could infect dogs via a scratch or bite,
as occurs with human cat scratch disease.
Transmission of B. henselae from cat to cat
and from cats to people is very well estab-
lished. However, future studies are needed
to define the route or routes of B. henselae
transmission to dogs.
In this study, the total B. henselae sero-
prevalence (23.5%) in dogs was much lower
than the seroprevalence (50%) found in cats
from the same geographical region [3, 34].
In humans, B. henselae seroprevalence ranges
between 5.7% in healthy human blood
donors  and up to 87% in human patients
with suspected cat scratch disease .
Cats appear to be the main reservoir of B.
henselae infection as indicated by the high
seroprevalences found in cats worldwide
 as well as documentation of persistent
bacteremia in naturally and experimentally
infected cats [1, 40, 43]. Bacteremia has
been infrequently documented in dogs, and
only by PCR amplification [6, 51]. The role
of dogs as a reservoir for B. henselae infec-
tion is unclear and needs further investiga-
This report describes statistically signif-
icant differences in B. henselae infection
between clinically healthy dogs selected for
lack to exposure to ticks or fleas and dogs
with clinical signs compatible with other
vector-borne diseases for which veterinar-
ians sought testing. This difference could be
related to selection bias; however, B. hense-
lae has been detected in several tissues from
sick dogs with a variety of clinical presen-
tations [24, 37, 51]. Further studies, such as
case-control studies, are needed to eluci-
date the clinical relevance of B. henselae
antibodies in dogs.
In humans, serological cross-reactions
between B. henselae and Coxiella burnetii
 and between B. quintana and Chlamy-
dia pneumoniae  have been reported.
There are no studies in cats or dogs that
assess the possibility of serological cross-
reactions between these or other bacterial
antigens. In the current study, based upon
testing of sera obtained from experimen-
tally infected dogs, there was no cross-reac-
tivity between R. rickettsii, E. canis and
B. henselae, and minimal cross-reactivity
between B. vinsonii subsp. berkhoffii and
B. henselae. However, the data provided on
cross-reactivity is not conclusive due to the
small sample size and the fact that the dogs
were experimentally inoculated and tested
in the acute phase of the infection. Due to
the limitations of this study, future investi-
gations should address the question of cross-
reactivity to ensure that the B. henselae
seroprevalence found in cats and dogs are
truly reflective of B. henselae exposure.
In this study, the presence of B. henselae
antibodies was associated with being sero-
reactive to R. rickettsii antigens. This asso-
ciation may indicate that R. rickettsii sero-
reactivity is due to cross-reactivity with R.
felis, R. typhi, other Rickettsia spp. or other
bacteria. These results might support simul-
taneous transmission of both Rickettsia and
Bartonella organisms to dogs by an insect
vector. It is well known that canine R. rick-
ettsii antibodies cross react with several
Rickettsia spp. of unknown pathogenicity
such as R. rhipicephali and R. montana .
In addition, flea-borne organisms (e.g., Yers-
inia pestis, R. typhi, R. felis and B. henselae)
are widely distributed throughout the world
in endemic disease foci. In the United States,
R. felis and R. typhi DNA has been found
in cat fleas  which supports the possibility
592L. Solano-Gallego et al.
that fleas may co-transmit B. henselae and
a Rickettsia spp. to dogs. Rocky Mountain
spotted fever is an important tick-borne
zoonosis that is especially prevalent in the
southeastern United States . In this study,
the seroprevalence of R. rickettsii antigen in
North Carolina was 29.7% in sick dogs. A
similar seroprevalence (29.8%) was found
previously in pet and stray dogs from North
Carolina . A lower R. rickettsii seroprev-
alence (14%) was found in the clinically
healthy dogs in this study.
Based upon current evidence, Bartonella
vinsonii subsp. berkhoffii has been consid-
ered the most frequent Bartonella species
infecting dogs . However, this conclu-
sion may not be accurate, as sera from dogs
have not been screened systematically against
a large panel of Bartonella species antigens.
B. vinsonii subsp. berkhoffii seroprevalence
in this study (4.7%) was similar to three pre-
vious reports [30, 31, 54] and was much
lower than the B. henselae seroprevalence
(23.5%) found in dogs in the current study.
Moreover, it is possible that an antibody
cross-reaction occurs between Bartonella
species as has been determined between
B. henselae and B. quintana in cats .
Recently, Bartonella washoensis was iso-
lated for the first time from the blood of a
dog with endocarditis . By IFA testing
that dog was strongly seroreactive to sev-
eral Bartonella antigens (B. vinsonii subsp.
berkhoffii, B. clarridgeiae and B. henselae)
suggesting exposure to several Bartonella spe-
cies or cross-reactivity between species .
However, the antibody titer to B. washoen-
sis was 1:8192 and to B. vinsonii subsp.
berkhoffii, B. clarridgeiae and B. henselae
1:4096 . In the present study, only two
dogs had a B. henselae titer of 1:4096, and
cross-reactivity might be less likely detected
at lower antibody titers. In this study, all
B. vinsonii subsp. berkhoffii seroreactive
sick dogs were concurrently seroreactive to
B. henselae antigens, but only 14.5% of
B. henselae seroreactors were also serore-
active to B. vinsonii subsp. berkhoffii. This
finding would tend to support unidirec-
tional cross-reactivity or co-exposure to
B. henselae in dogs infected with B. vinso-
nii subsp. berkhoffii.
In this study, E. canis seroprevalence
(6.5%) in sick dogs was slightly greater
than from a previous report (2.4%) of sick
dogs also living in North Carolina .
Detection of B. henselae antibodies was
associated with seroreactivity to E. canis
antigens. This association may support tick
transmission of B. henselae in some cases,
as Ehrlichia spp. are transmitted by ticks
. Babesia canis (0.85%) and B. burg-
dorferi (1.7%) antibodies were infrequently
detected; further, C6 peptide seropreva-
lence was slightly lower than the B. burg-
dorferi IFA prevalence from the same area
(2.5%) although these results are difficult to
compare due to the fact that different sero-
logical tests were employed .
In conclusion, this study indicates that
B. henselae IgG antibodies are prevalent in
healthy and sick dogs living in the southeast
region of the USA. Bartonella henselae
seroprevalence seems greater in dogs with
clinical signs compatible with arthropod
vector-borne diseases than in healthy dogs,
selected for infrequent exposure to ticks or
fleas. Based upon testing sera from experi-
mentally infected dogs, there does not appear
to be cross-reactivity between B. henselae
and B. vinsonii subsp. berkhoffii, E. canis or
R. rickettsii. Currently, there is a signifi-
cant, but unexplained, association between
B. henselae and R. rickettsii antibodies in
sick dogs from the southeastern USA. Fur-
ther studies are needed to evaluate the epi-
demiological, clinical, and zoonotic rele-
vance of B. henselae infection in dogs.
The authors gratefully acknowledge Dr Guptill-
Yoran and Mrs. Ashlee Duncan for reviewing
this manuscript and Dr Chomel for providing
sera samples from dogs experimentally infected
with B. henselae. Laia Solano-Gallego was sup-
ported financially by a grant from La Caixa bank
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