RI infections are deadly to snakes and can quickly deteriorate your ball pythons health. It's a good thing that you are addressing the symptom early on, as the evidence of foaming saliva outside the mouth is usually an indication of an advanced RI. Until you can get help from a vet (soon that is), try bumping up the humidity a bit and increasing the basal aquarium temp. Once you get it on a Rx regimen, disinfect the cage daily (I keep secondary, open tubs readied) and change the water often. I wish your bp has a speedy recovery.