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-pathogenfree (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.

The isolation of Bartonella henselae, the agent of cat scratch disease, from the blood of naturally infected domestic cats and the demonstration that cats remain bacteremic for several months suggest that cats play a major role as a reservoir for this bacterium. A convenience sample of 205 cats from northern California was selected between 1992 and 1994 to evaluate the B. henselae antibody and bacteremia prevalences and to determine the risk factors and associations between bacteremia and antibody titers. B. henselae was isolated from the blood of 81 cats (39.5%). Forty-two (52%) of these bacteremic cats were found to be infected with >1,000 CFU/ml of blood. Impounded or former stray cats were 2.86 (95% confidence interval [CI] ‫؍‬ 1.94, 4.22) times more likely to be bacteremic than the pet cats. Young cats (<1 year old) were more likely than adult cats to be bacteremic (relative risk ‫؍‬ 1.64; 95% CI ‫؍‬ 1.19, 2.28). Bacteremic cats were more likely than nonbacteremic cats to be infested with fleas (relative risk ‫؍‬ 1.64; 95% CI ‫؍‬ 1.38, 1.96). No association between B. henselae infection and feline immunodeficiency virus antibody prevalence was observed. Eighty-one percent of the cats (166 of 205) tested positive for B. henselae antibodies, and titers were higher in bacteremic than in nonbacteremic cats. Multiple logistic regression analysis indicated that younger age and seropositivity for B. henselae antibodies were associated with bacteremia. Serological screening for Bartonella antibodies may not be useful for the identification of bacteremic cats (positive predictive value ‫؍‬ 46.4%), but the lack of antibodies to B. henselae was highly predictive of the absence of bacteremia (negative predictive value ‫؍‬ 89.7%). Seronegative cats may be more appropriate pets for immunocompromised individuals who are at increased risk for developing severe B. henselae disease.

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Plague impacts prairie dogs (Cynomys spp.), the endangered black-footed ferret (Mustela nigripes) and other sensitive wildlife species. We compared efficacy of prophylactic treatments (burrow dusting with deltamethrin or oral vaccination with recombinant “sylvatic plague vaccine” [RCN-F1/V307]) to placebo treatment in black-tailed prairie dog (C. ludovicianus) colonies. Between 2013 and 2015, we measured prairie dog apparent survival, burrow activity and flea abundance on triplicate plots (“blocks”) receiving dust, vaccine or placebo treatment. Epizootic plague affected all three blocks but emerged asynchronously. Dust plots had fewer fleas per burrow (P < 0.0001), and prairie dogs captured on dust plots had fewer fleas (P < 0.0001) than those on vaccine or placebo plots. Burrow activity and prairie dog density declined sharply in placebo plots when epizootic plague emerged. Patterns in corresponding dust and vaccine plots were less consistent and appeared strongly influenced by timing of treatment applications relative to plague emergence. Deltamethrin or oral vaccination enhanced apparent survival within two blocks. Applying insecticide or vaccine prior to epizootic emergence blunted effects of plague on prairie dog survival and abundance, thereby preventing colony collapse. Successful plague mitigation will likely entail strategic combined uses of burrow dusting and oral vaccination within large colonies or colony complexes.Electronic supplementary materialThe online version of this article (doi:10.1007/s10393-017-1236-y) contains supplementary material, which is available to authorized users.