Is he who goes to the hospital for treatment of a scorpion or snake bite, instead of ruqyah with salted water and the two surahs of seeking refuge (Al-Mu'awwidhatayn), considered a disbeliever or one who believes that guidance other than that of the Prophet, may Allah bless him and grant him peace, is better than his guidance?

Merely taking the means of treatment does not constitute disbelief (kufr), for Allah has legislated treatment for illnesses, and this has been established through the actions of the Prophet (peace be upon him) and his Companions. There is no contradiction between medical treatment and ruqyah (Islamic incantation). None of the people of knowledge have said that it is obligatory to rely solely on ruqyah. As for ruqyah with salty water, we do not know of anything authentic regarding it.