Acute clinical disease in cats following infection with a pathogenic strain of Bartonella henselae (LSU16).

Bartonella henselae is the causative agent of human cat scratch disease as well as several serious sequelae of infections, including bacillary angiomatosis and bacillary peliosis. Conflicting reports describe the pathogenesis of B. henselae in the cat. In this study, we characterized a strain of B. henselae termed LSU16. This strain was isolated on rabbit blood agar from a naturally infected 10-month-old female cat during a recurrent episode of bacteremia. The bacterial species was confirmed by PCR-restriction fragment length polymorphism analysis. Nine cats were infected intradermally with 5 x 10(7) CFU of LSU16, and clinical signs, antibody responses, and bacteremia were monitored. All nine cats developed raised, erythematous areas at the site of inoculation within 72 h postinoculation; the swelling peaked at 14 days postinfection and was not palpable by 28 days postinfection. Fever developed in all nine cats between 6 and 16 days postinfection and lasted for 1 to 8 days. Between 6 and 16 days postinfection, all nine cats experienced lethargy which persisted 5 to 18 days. Seven of nine cats were bacteremic by day 7, and all nine cats had become bacteremic by 14 days postinfection. Bacteremia peaked at 14 to 28 days postinfection in all cats. In six of the nine infected cats, bacterial numbers reached nondetectable levels during the 7th week postinfection; however, a single animal maintained bacteremia to 18 weeks postinfection. All nine cats developed strong antibody responses to B. henselae, as determined by Western blot analysis and enzyme-linked immunosorbent assay. Subsequently, three naive cats were injected intradermally with blood from cats infected with LSU16 from a pure culture, and five naive cats were injected with feces from fleas which had been feeding on cats infected with a pure culture of LSU16. These cats developed signs similar to those described in the previous experiment and were euthanized at 5 weeks postinfection. We conclude that B. henselae LSU16 is a virulent strain of B. henselae in cats and propose that the virulence of B. henselae in cats is strain dependent.

Experimental infection of domestic cats with Bartonella henselae by inoculation of Ctenocephalides felis (Siphonaptera: Pulicidae) feces.

Caged cat fleas, Ctenocephalides felis (Bouché), were fed on 6 cats; 3 cats were injected with 5 x 10(7) colony forming units of Bartonella henselae intradermally and 3 cats were injected with an equal volume of saline. After the fleas fed for 4 d, 5 groups of 50 B. henselae-exposed fleas were caged and allowed to feed on 5 cats for 6 d. Five cats each were injected intradermally with 1 ml of saline containing 45 mg of feces from B. henselae-exposed fleas. Five cats were fed 50 B. henselae-exposed fleas and 45 mg of fresh feces from B. henselae-exposed fleas. Five cats received all 3 treatments by using fleas and feces collected from cats inoculated with saline (controls). Cats were bled weekly and tested by culture and serology. The cats that were injected with feces from infected fleas were positive by culture for B. henselae at 1 or 2 wk after exposure and were the only cats to become bacteremic or seropositive by week 20.