Evaluation of topical application of 10% imidacloprid-1% moxidectin to prevent Bartonella henselae transmission from cat fleas.

To determine whether monthly topical administration of a combination of 10% imidacloprid and 1% moxidectin would lessen flea (Ctenocephalides felis) transmission of Bartonella henselae among cats. Controlled trial. 18 specific pathogen-free cats housed in 3 groups of 6. 3 enclosures were separated by mesh to allow fleas to pass among groups yet prevent cats from contacting one another. One group was inoculated IV with B henselae, and after infection was confirmed, the cats were housed in the middle enclosure. This infected group was flanked by a group that was treated topically with 10% imidacloprid-1% moxidectin monthly for 3 months and by an untreated group. On days 0, 15, 28, and 42, 100 fleas/cat were placed on each of the 6 cats in the B henselae-infected group. Blood samples were collected from all cats weekly for detection of Bartonella spp via PCR assay, bacterial culture, and serologic assay. B henselae infection was confirmed in the cats infected IV and in all untreated cats after flea exposure; none of the cats treated with the imidacloprid-moxidectin combination became infected. In this setting, monthly topical administration of 10% imidacloprid-1% moxidectin reduced flea infestation, compared with infestation in untreated cats, and thus prevented flea transmission of B henselae to treated cats. Regular monthly use of this flea control product in cats may lessen the likelihood of humans acquiring B henselae infection.