[matese]

If you have mice all year round your dad has to find where they are coming in which I am very sure he has already done this and sealed all openings. He has to look further to find where they are entering the home. If you only get them when the weather gets cold that's normal for mice to seek a warm house for the winter. It doesn't matter that no food is left out, they are seeking shelter from the cold. If your dad cannot find where they are coming in he can hire an exterminator they usually can tell / find where they are entering and seal that entrance. These are field mice entering your home. Setting out traps in areas where the dogs cannot get access to is the only choice you have. I wouldn't do the Lepto vaccine unless all or some of your pups were catching several mice a week. Keep your eye on Ollie, he'll be sniffing around looking for another one, check the areas he sniffs at.