Should I be concerned. I have been using frontline because that's what the people I got sophie from used. She scratches, I never see anything except for bug like things, dead, could be fruit flies, could be dead fleas???? anyway, should I be worried about heartworm? do I need to switch to revolution or just keep it as is. Summer's coming eventually, just wondering, please help? it costs the same as frontline...thanks in advance.