Results (mean and standard deviation) of Ctenocephalides felis counts over time after placement of a flea collar on cats housed in R3 which was adjacent to R1 and R2. The 4 cats in R2 had been experimentally infected with Bartonella henselae and a total of 50 males and 50 female C felis were placed on the R2 cats on Day 0, monthly for an additional 6 applications and then every 12 – 14 days for 4 applications. There were 6 – 7 cats in R1 over the course of the study. Only one C. felis was found on one cat in R3 over the course of the study (Day 238). The only day that C. felis counts were significantly different amongst groups was on Day 14 when cats in R2 had greater numbers of C. felis than cats in R1 or R3.