The verse most specific to a "built in" reaction to snake/snake like patterns (per OP) is Genesis 3:15:
"I will put enmity between you and the woman,
and between your offspringe and her offspring;
he shall bruise your head,
and you shall bruise his heel." (ESV)
"I will put enmity between you and the woman, and between your offspringe and her offspring; he shall bruise your head, and you shall bruise his heel." (ESV)