The CDC confirmed that the black legged deer tick not only can transmit Borrelia burgdorferi, the causative agent of Lyme disease but also a related bacteria named Borrelia mayonii after the Mayo Clinic physicians who discovered and identified it. Borrelia mayonii has been isolated from 6 patients, none of whom had the infamous bullseye rash seen in 1/3 of the Lyme cases. These patients experienced vomiting, diffuse rashes and a higher concentration of bacteria in the blood that that reported for Borrelia mayonii infections.
The CDC advises that the new bacteria can be treated with the same antibiotics effective against Lyme disease and that tests for Lyme should be as effective at detecting Borrelia mayonii as detecting Borrelia burgdorferi (testing has many false negatives). A screen of blood from 43,000 samples of people suspected of having Lyme disease failed to find additional instances of Borrelia mayonii. So far, the new bacteria has only been found in MN and WI. Those who go in wooded areas when ticks are active should use tick repellents as a precaution.