What are long term effects of untreated Lyme disease?

Highly variable. Some with untreated lyme disease have minimal or no symptoms- a healthy person with a strong immune system can co-exist with it. Others can have devastating symptoms: fatigue, muscle/joint pains ; neurological symptoms ranging from poor memory/concentration to symptoms that mimic ms or als. Those with genetic susceptibilities, co-infections, toxic exposures, stress etc. Will have worse symptoms.