Infection and re-infection of domestic cats with various Bartonella species or types: B. henselae type I is protective against heterologous challenge with B. henselae type II

Four Bartonella species have been isolated from domestic cats, of which two serotypes/genotypes of Bartonella henselae and possibly B. clarridgeiae are human pathogens, causing cat scratch disease (CSD). Our objectives were to evaluate infection and potential cross-protection during re-infection in domestic cats with various Bartonella species or types. Thirty-six cats were primarily inoculated with B. henselae type I (n = 16), B. henselae type II (n = 10), B. clarridgeiae (n = 6) or B. koehlerae (n = 4). They were challenged with B. henselae type I (n = 15), B. henselae type II (n = 13) or B. clarridgeiae (n = 8). All 36 cats became bacteremic (1.25 x 10(2)-1.44 x 10(6) CFU/ml) and bacteremia lasted from 37 to 582 days. Duration of bacteremia for cats inoculated with B. henselae type I was shorter than for cats inoculated with either B. henselae type II (P = 0.025) or B. clarridgeiae (P = 0.011). After challenge, 26 cats became bacteremic. Among the nine cats primarily inoculated with B. henselae type I and challenged with B. henselae type II, six cats stayed abacteremic. The three bacteremic cats had a transient low-level bacteremia. No bacteremia was observed in three cats primarily inoculated with B. henselae type I and challenged with another strain of B. henselae type I. Bacteremia levels in the 26 cats were significantly lower than for primary inoculation (P = 0.022) and its duration was shorter (P = 0.012). Among the eight cats challenged with B. clarridgeiae, duration of bacteremia in the four cats primarily inoculated with B. henselae type I was shorter than in the four cats primarily inoculated with B. henselae type II (P = 0.01). Bartonella clarridgeiae inoculated cats were more likely to have relapses for both primary and secondary infections. This is the first demonstration of cross-protection, evidenced by absence of bacteremia, in cats primarily infected with B. henselae type I and challenged with B. henselae type II, whereas no cross-protection was previously shown for cats primarily infected with B. henselae type II and challenged with B. henselae type I. Such results are of major importance for future feline Bartonella vaccine development.