But basically this is a bacteria that exists in various rodent populations, some cute, some not so cute like the black rat. And it attacks fleas and it blocks up the mid-gut section of the flea. The flea then tries to eat, it can't, it keeps trying to suck blood. It throws up that bacteria into the rodent it's living on and then that rodent's going to die. And then the flea has to find somewhere else to go. And if there's no humans around, it's kind of all good. It really doesn't bother anybody.