Lots of patients are testing positive for Rocky Mountain Spotted Fever. Patients universally have low positive titers. I do not think most have ever had the disease. There are many tick borne diseases yet unknown or undiscovered. A Rickettsia bacteria, unclassified, has been reported in a European species of Ixodes ricinus. This is a novel find.
Rocky Mountain Spotted Fever (RMSF) is caused R. rickettsia. Patients have spots on their hands which spread to their trunk and these patients are frequently critically ill. Rickettsia species cause other diseases including typhus. RMSF is not known to be transmitted by small tick, deer ticks or lone start ticks, but transmitted by larger ticks like wood ticks/dog ticks.
I think these positive results are due to cross-reactivity with some yet unknown form of Rickettsia carried by deer ticks. Some species of Rickettsia may cause little or no clinical illness. Low positive serology for RMSF may be another marker for the presence of tick borne illness in general.
Like other tick-borne co-infections ( like Anaplasma) , Rickettsia species are all sensitive to doxycycline.
For this reason, a course of doxycycline should always be incorporated in an antibiotic program used in the treatment of Lyme disease and tick borne illnesses.