> any measure that works against one would work against all Modulo any environmental or self-mutation factors, I suppose? Might be that a tick which sucks blo

> any measure that works against one would work against all Modulo any environmental or self-mutation factors, I suppose? Might be that a tick which sucks blood from deer with XYZ picks up a parasite or bacteria which protects it against your measure. Or one crawls through some chemical goop / radioactive slop / gets hit by a cosmic ray etc. and gets a mutation which helps. (Both fairly unlikely, I'll grant, but when you're dealing with millions or billions of ticks, unlikely is likely to happen a lot.)