Can't believe this but both cats have huge fleas despite using prescription spot on treatment. On vet's advice have given treatments with 3 week interval not 4. Most recent one was 3 days ago - still alive and well fleas on cats when I combed them this evening. Have sprayed house with Indorex and washed bedding etc. I know more will hatch for ages but I thought they are supposed to die when they bite the cat.