This controlled prospective trial investigated the ability of topical monthly administration of 10% imidacloprid–1% moxidectin (Advocate; to lessen the transmission of Bartonella henselae between specific pathogen-free cats housed in 3 groups. Of 18 cats, 6 were infected with IV administration of B henselae isolated through DNA amplification of feline blood taken from a shelter in Florida. These 6 cats were also infected with fleas (Ctenocephalides felis) and housed in a carpeted area to facilitate flea life cycles. The groups of cats were separated from each other by a mesh screen. Six other cats were given 10% imidacloprid–1% moxidectin at regular intervals, and the other 6 were left untreated. Most cats in the untreated group and the B hensalae–infected group had fleas during the experimental period. This finding confirmed that transmission of fleas through the mesh was successful. In addition, all cats in the untreated group tested positive for B henselae through blood culture and DNA amplification, and 3 of 6 cats became ill during the study period. One cat was euthanized after it developed pleural effusion, pericardial effusion, suppurative myocarditis, and cholangiohepatitis. All cats in the 10% imidacloprid–1% moxidectin group tested negative for B henselae, except for 1 that had a transiently positive serologic test result. None of the treated cats became ill, and none of the experimentally inoculated or flea-exposed cats became ill. Study supported by Bayer Animal Health

Commentary: This study supports previous studies showing flea transmission of B henselae in cats and that the use of a monthly topical preventive agent lessened transmission between cats in a controlled setting. However, the causal relationship between clinical disease in cats and Bartonella species is still an important area of evolving research. As a result, the relative importance of prevention is still up for debate, especially for the pet owner who has financial or logistical pet care concerns. Obviously, prevention of ectoparasites in exposed cats would be important for many other reasons in addition to Bartonella prevention and should therefore be advised.

Evaluation of topical application of 10% imidacloprid-1% moxidectin to prevent Bartonella henselae transmission from cat fleas. Bradbury CA, Lappin MR. JAVMA 236:869-873, 2010.