1990: CDC publishes a Lyme case definition that recognizes it as "relapsing fever."
Here the published surveillance case definition is based on Allen Steere's 1986 report, "Antigens of Borrella burgdorferi Recognized during Lyme Disease."
They say, just do repeat Western Blots to look for new IgM bands, because that meant the bug was still alive after treatment.
See Steere's page here.
To be clear, all Borreliae are relapsing fever organisms, and the nature of the relapse is antigenic variation. Therefore you cannot use any DNA from plasmids – which is where the variable surface antigens are ordered manufactured and remanufactured – to assess for spirochetes. No one sane does this. No researchers outside the United States EVER uses plasmid DNA to assess for spirochetes. They only use species-specific spacer genes like 5, 16 and 23 S RNA or flagellin. That’s it.