Harris has appealed her fans to get tested for the condition - which can affect the skin, joints, heart, and nervous system - after learning she had contracted it without realising.
"If you have EVER GONE HIKING, please get tested for #LymeDisease... I was diagnosed a few days ago and have a long road ahead of me. Supposedly you get it from ticks but I have absolutely no recollection of being bit or having a rash or ANYTHING.
"...The symptoms are vast and when it has been left untreated for a long time can turn into MS, Alzheimer's, Parkinson's, Dementia and ALS.
Harris, who married the media mogul in December 2012, is relieved to have a diagnosis after years of being told it was "all in her head" and feeling like a "hypochondriac".
"It is a disease so many people are living with and is becoming an epidemic. I always thought I was a hypochondriac.