Prevalence of Bartonella henselae antibodies in pet cats throughout regions of North America

Experimental transmission of Bartonella henselae by the cat flea

Bartonella henselae is an emerging bacterial pathogen, causing cat scratch disease and bacillary angiomatosis. Cats bacteremic with B. henselae constitute a large reservoir from which humans become infected. Prevention of human infection depends on elucidation of the natural history and means of feline infection. We studied 47 cattery cats in a private home for 12 months to determine the longitudinal prevalence of B. henselae bacteremia, the prevalence of B. henselae in the fleas infesting these cats, and whether B. henselae is transmitted experimentally to cats via fleas. Vector-mediated transmission of B.henselae isolates was evaluated by removing fleas from the naturally bacteremic, flea-infested cattery cats and transferring these fleas to specific-pathogen-free (SPF) kittens housed in a controlled, arthropod-free University Animal Facility. B. henselae bacteremia was detected in 89% of the 47 naturally infected cattery cats. A total of 132 fleas were removed from cats whose blood was simultaneously cultured during different seasons and were tested individually for the presence of B. henselae DNA by PCR. B. henselae DNA was detected in 34% of 132 fleas, with seasonal variation, but without an association between the presence or the level of bacteremia in the corresponding cat. Cat fleas removed from bacteremic cattery cats transmitted B. henselae to five SPF kittens in two separate experiments; however, control SPF kittens housed with highly bacteremic kittens in the absence of fleas did not become infected. These data demonstrate that the cat flea readily transmits B. henselae to cats. Control of feline infestation with this arthropod vector may provide an important strategy for the prevention of infection of both humans and cats.

Bartonella henselae infection in cats: evaluation during primary infection, treatment, and rechallenge infection

Bartonella henselae infection was established in eight cats of various ages by experimental inoculation. All cats remained persistently bacteremic until they were treated 4 to 7 weeks after primary inoculation. Antibody titers increased and peaked between 4 and 12 weeks for all cats. Treatment with doxycycline for 1 week was effective in suppressing bacteremia in all cats but was effective in clearing infection from only four cats. Amoxicillin, given subsequently, was effective in clearing the infection from three of the remaining cats. One kitten that remained bacteremic was treated unsuccessfully with enrofloxacin, and its bacteremia was finally cleared when it was treated with a clavulanate-amoxicillin combination. After the bacteremia was cleared, with a corresponding reduction in serum antibody titers, all eight cats were rechallenged with B. henselae. None of the cats became bacteremic after secondary challenge, and all had higher and more rapid increases in serum antibody titers than after primary inoculation. The cats became resistant to reinfection following recovery from infection, indicating that immunoprophylaxis in cats might be beneficial in helping to reduce their public health risk.

Comparative seroreactivity to Bartonella henselae and Bartonella quintana among cats from Israel and North Carolina

Bartonella henselae, the predominant cause of cat scratch disease, and Bartonella quintana, the cause of trench fever, are closely related Bartonella species that induce cross-reactivity when cat or human sera are tested using an indirect immunofluorescence antibody (IFA) test. Cats are the natural reservoir for B. henselae, whereas a mammalian reservoir host for B. quintana has not been identified. Serum samples from 114 cats from Israel and 114 cats from North Carolina were tested by IFA for seroreactivity to B. henselae and B. quintana antigens. Similar numbers of cats from Israel [45 (39.5%)] and from North Carolina [46(40.4%)] were seroreactive to both antigens, however, as compared to cats from North Carolina [8 (7%)], a significantly (P = 0.001) larger number of cats from Israel were seroreactive to B. quintana antigen only [23 (20.2%)]. In addition, mean antibody titers were lower to B. henselae than to B. quintana (P = 0.0001) in the cats from Israel, whereas similar mean titers to both antigens were identified in cats from North Carolina. Absorption of serum using whole B. henselae organisms resulted in a significantly greater (P = 0.0001) decrease in antibody titer to B. henselae between absorbed and non-absorbed sera, as compared to the decrease in antibody titer following absorption with whole B. quintana organisms. There was a similar decrease in antibody titer in sera from cats experimentally infected with B. henselae and in cats naturally exposed to Bartonella species from Israel and North Carolina. Our results indicate that absorption of serum will, in most instances, distinguish species-specific reactivity by IFA to B. henselae from cross-reactivity to B. quintana in cats experimentally infected with B. henselae. The data support the conclusion that B. henselae is the principal Bartonella species responsible for seroreactivity against B. henselae and B. quintana in naturally exposed cats from Israel or North Carolina. It also suggests that in Israel, cats are exposed to one or more antigenically different Bartonella species, sub-species or strains, that seroreact by IFA more intensely with B. quintana antigen.