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Clinical and Diagnostic Laboratory Immunology, March 2004, p. 423-425, Vol. 11, No. 2
1071-412X/04/$08.00+0 DOI: 10.1128/CDLI.11.2.423-425.2003
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Prevalence of Bartonella clarridgeiae and Bartonella henselae in Domestic Cats from France and Detection of the Organisms in Erythrocytes by Immunofluorescence
Jean-Marc Rolain,1 Caroline Locatelli,2 Luc Chabanne,2 Bernard Davoust,3 and Didier Raoult1*
Unité des Rickettsies CNRS UMR-A 6020, IFR 48, Faculté de Médecine, Université de la Méditerranée, 13385 Marseille Cedex 05,1
Ecole Nationale Vétérinaire de Lyon, Département des Animaux de Compagnie-Médecine Interne, Responsable des Unités Clinique et Pédagogique, 69280 Marcy l'Etoile,2
Conseiller Vétérinaire Régional Interarmées, 69998 Lyon Armées, France3
Received 3 September 2003/
Returned for modification 11 November 2003/
Accepted 19 November 2003

ABSTRACT
The prevalence of
Bartonella infection in a pet cat population
from France was found to be 8.1% (8 of 99 cats). The intraerythrocytic
location of
Bartonella clarridgeiae is shown for the first time,
and we show that immunofluorescence detection of the organism
in erythrocytes correlates with the number of bacteria in blood.

INTRODUCTION
Bartonella species are facultative intracellular bacteria highly
adapted to their reservoir hosts, in which the bacteria can
cause a long-lasting intraerythrocytic bacteremia (
6,
10). Four
species of the genus
Bartonella have been recovered from the
blood of cats:
Bartonella henselae, the agent of cat scratch
disease (
20);
B. clarridgeiae (
16);
B. bovis ("
B. weissii")
(R. Regnery, N. Marano, P. Jameson, E. Marston, D. Jones, S.
Handley, C. Goldsmith, and C. Greene, 15th Meet. Am. Soc. Rickettsiol.,
p. 15, 2000); and
B. koehlerae (
7,
22). The vector of
B. henselae is the cat flea (
Ctenocephalides felis) (
5). The cat flea may
also be the vector for
B. clarridgeiae and
B. koehlerae (
23).
The prevalence of
Bartonella bacteremia in apparently healthy
cats varies from 4 to 70%, depending on the geographical location
and the cat population studied (stray cats or pet cats) (
3,
18). In specific hosts, the target cells for
Bartonella are
either endothelial cells or red blood cells (
6). Both
B. henselae and
B. koehlerae have previously been shown to be located in
the erythrocytes of cats (
13,
19,
22,
24,
27), and
B. quintana and
B. bacilliformis have been shown to be located in the erythrocytes
of humans (
1,
21,
25). In this study we have evaluated the prevalence
of
Bartonella infection in a well-defined urban pet cat population
by blood culture and detection of the organism in erythrocytes
by immunofluorescence.
The study was performed between March and November 2002 at the National Veterinary School of Lyon, Lyon, France. All pet cats were anesthetized before 3 ml of fresh blood was collected aseptically from the external jugular vein and placed in vials containing EDTA. Upon receipt of the samples, five thin blood smears were made for each cat and were air dried and stored at room temperature until the direct immunofluorescence assays were carried out. The immunofluorescence assay (Axioskop 20; Carl Zeiss, Göttingen, Germany) and laser confocal microscopy were performed as described previously (24) with a mouse monoclonal antibody (monoclonal antibody B3D4) specific for the Bartonella genus (monoclonal antibody titer, 1/1,600 diluted 1/400 in phosphate-buffered saline). Isolation of the bacteria was carried out by using Columbia 5% sheep blood agar plates (Biomerieux, Marcy l'Etoile, France) (24). When Bartonella-like colonies were observed, the numbers of CFU were recorded. Isolates were characterized by sequencing of their 16S-23S intergenic spacer region genes by using the BLAST (version 2.0) program (National Center for Biotechnology Information) (26). Student's t test was performed with EpiInfo software (version 6) for comparison of the laboratory data. A difference was considered significant when P was <0.05.
A total of 99 domestic indoor cats from the area of Lyon, France, were included in the study. Fleas were found on only two cats. Most cats were European breeds (94%) and were presented for sterilization (74%). The sex ratio of the cats was of 0.87 (males to females). The ages of the cats ranged from 3 months to 17 years (mean age, 2.97 ± 3.65 years) with 48.8% of the cats being under 1 year of age (young cats). Eight cats (8.1%) yielded a positive blood culture result, with six being infected with B. henselae Houston-1 (GenBank accession number L35101) and two being infected with B. clarridgeiae (GenBank accession number AF312497) (Table 1). The geometric mean number of CFU for the six B. henselae (22 CFU) isolates was significantly lower than that for the two B. clarridgeiae isolates (3,162 CFU; 95% confidence interval, [CI], 20 to 192). The ages of the bacteremic cats ranged from 9 months to 10 years (average, 4.11 ± 3.74 years), with only one bacteremic cat (which was positive for B. clarridgeiae) being under 1 year of age. Of the eight cats found to be bacteremic by culture, four, including the two B. clarridgeiae-infected cats, were also positive by immunofluorescence with the Bartonella genus-specific monoclonal antibody (Fig. 1). The mean percentage of infected red blood cells for the four positive cats was 1.02% ± 1.55% (range, 0.03 to 3.7%). The intraerythrocytic location of B. clarridgeiae was confirmed by laser confocal microscopy (Fig. 1). The geometric mean number of CFU for cats that were positive by immunofluorescence (532 CFU) was significantly higher than that for cats that were negative (11 CFU; 95% CI, 9 to 274 CFU).
We found that prevalence of
Bartonella bacteremia among cats
in France was lower (8.1%) than that reported previously (
9,
15). Factors which appear to influence the prevalence of bacteremia
include geographical location, cat population, cat age, and
levels of flea infestation. For example, a low prevalence (7.2%)
of bacteremia in pet cats in Japan has been reported (
17), whereas
prevalences higher than 60% have been reported in the United
States, Europe, and Southeast Asia (
3,
9,
15). It has been shown
that seropositivity for
Bartonella correlates with increasing
climatic temperatures and annual levels of precipitation (
11).
Such variations in the prevalence of bacteremic cats in areas
with different climates have also been demonstrated in European
countries (
4). Variations in cat populations may explain the
differences in the prevalences of bacteremia, with pet cats
less likely to be bacteremic than stray cats (
3). Although kittens
and young cats have been found to be bacteremic more frequently
than older cats (
9,
12,
28), such a correlation was not found
in the present study. However, our preliminary results are consistent
with those of previous reports (
12,
14) that showed that older
animals more often have chronic infections with lower concentrations
of bacteria. This difference in the levels of bacteremia in
cats with acute and chronic infections has also been described
in humans with trench fever due to
B. quintana (
2,
8). The low
prevalence of infections found in our study might have been
due to the fact that the cats that we studied were mostly indoor
cats that were not infested with fleas (only two cats had fleas).
In our study we were also able to demonstrate for the first
time the intraerythrocytic location of
B. clarridgeiae (Fig.
1). The sensitivity of immunofluorescence detection compared
to that of culture detection of
Bartonella was 50%, similar
to that reported for the detection of chronic bacteremia due
to
B. quintana in homeless people (
21).
In conclusion, our study has shown a low prevalence of bacteremia due to Bartonella species in a well-defined pet cat population. Our study confirms that indoor pet cats are less frequently infected than stray cats. We found that B. clarridgeiae infections result in greater bacteremic loads than B. henselae infections. Immunofluorescence detection of the bacteria in erythrocytes was correlated with the bacteremic load.

ACKNOWLEDGMENTS
We thank Patrick Kelly for reviewing the manuscript.

FOOTNOTES
* Corresponding author. Mailing address: Unité des Rickettsies, Faculté de Médecine, 27, Blvd. Jean Moulin, 13385 Marseille Cedex 5, France. Phone: 33 04 91 32 43 75. Fax: 33 04 91 38 77 72. E-mail:
Didier.Raoult{at}medecine.univ-mrs.fr.


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Clinical and Diagnostic Laboratory Immunology, March 2004, p. 423-425, Vol. 11, No. 2
1071-412X/04/$08.00+0 DOI: 10.1128/CDLI.11.2.423-425.2003
Copyright © 2004, American Society for Microbiology. All Rights Reserved.