Usually means lyme
is caused by a tick (most commonly on deer or dog) that carries the spirochete (borrelia burgdorferi).
The tick must get its prongs into you for at least a few hours, suck enough of your blood that it gets engorged, then 'regurgitates' the blood with the spirochete into your body. If your immune system doesn't kill that spirochete, you get lyme disease. Rx early is important.