Flea Screen combo Spot-on treatment for cats kills fleas on treated cats and prevents eggs laid by fleas exposed to Flea Screen combo from developing for up to 6 weeks. Kills ticks on treated cats for up to 2 weeks and infestations of biting lice. Flea Screen combo is a spot-on treatment that is applied between the shoulder blades. It is suitable for use in households with both cats and dogs. Available in one size for cats weighing 1-8kg.