Poison effect detection?

I am looking to make a procedure that will trigger when the player has a poison effect of my choice.  When the player has bad omen, I want a mob I made to spawn. I may do the same for blindness & nausea.  I want it to only trigger if the player has the right poison effect & spawn the correct mob close to the players location.

Is there any way to set that up or something close to this sort of trigger.   How can we detect if the player has a poison effect? Then trigger this only one time, well not removing the effect?