Seroprevalence of Bartonella spp. in the endangered island fox ( Urocyon littoralis)

Bartonella clarridgeiae-like strains, presently B. rochalimae, were isolated in gray foxes ( Urocyon cinereoargenteus) in mainland California. The objective of this study was to investigate the presence of Bartonella infection in the endangered island fox ( Urocyon littoralis) found only on the Channel Islands off the Californian coast. Between 2001 and 2004, 263 serum samples were collected. Antibodies against Bartonella vinsonii subsp. berkhoffii (Bvb) and B. clarridgeiae (Bc) were detected using an immuno-fluorescence antibody test. Sixty-eight (25.8%) and 73 (27.7%) foxes were positive for Bvb and Bc, respectively. Seroprevalence was the highest on Santa Cruz Island ( n = 36, Bvb = 80.5%; Bc = 86.1%) and Santa Rosa Island ( n = 38, Bvb = 52.6%; Bc = 65.8%). On San Miguel and San Clemente Islands, seroprevalence for Bvb was 20% and 17.3% respectively, and 0% and 21.3% for Bc. Prevalence ranged between 0% and 5.1% on San Nicolas and Santa Catalina Islands. Foxes from Santa Rosa and Santa Cruz Islands were 17.5 times and 31.5 times as likely to be seropositive for Bvb and Bc than foxes from the other islands (95% confidence interval [95% CI] = 8.5, 36.7; 14.4, 70.2). There were no statistically significant differences for presence of Bartonella antibodies by sex, age, origin (captive vs. wild) or year of blood collection. This is the first report of exposure to Bartonella in the island fox population. Further studies are necessary to isolate these bacteria from foxes and determine factors associated with presence or absence of Bartonella species on specific islands.