Thrush is not contagious. As far as replacing your toothbrush, that may be a good habit, having suggested it before, and for other bacteria, infections, but for thrush, everyone's body has candida anyway, needs it, balances it, and just gets out of control when our bodies can't manage the flora balance anymore due to our compromised immune system, medications, treatments, and others. So wether you replace your toothbrush, you will still have thrush until your body can balance the candida flora. The same with someone with thrush can't infect another person, and if so, they probably already had it or were immunocompromised.

I hope this helps.