Why is Reverend parris so concerned that there be no talk of "unnatural causes" when bettys illness is concerned?

Parris has sent for Reverend Hale of Beverly, who will confirm the possibility of an unnatural cause of Betty's illness, but he orders Susanna to say nothing of unnatural causes to others. The fact that Betty looks "bewitched" would point directly to Parris letting witchery go on under his watch as the head of the church. Parris is afraid for his job and reputation.