After the bite of an insect infected with Borrelia, the germs first spread in the skin (approx. 72 hours) and then via the bloodstream into other tissues. Under certain circumstances, they may later infect various organs. In some cases, the infection spreads to the nervous system.

Some patients – with or without erythema migrans – experience general symptoms of illness in the first few weeks after infection, such as fatigue, mild fever, muscle and joint pain, headache, sweating, conjunctivitis, gastrointestinal complaints and swelling of the lymph nodes.

The eryththema migrans, a disc-shaped reddening of the skin with a white circle, usually only occurs after a second contact with the Borrelia bacteria, so it can also be absent.

In case of a tick bite, it makes sense to send in the removed tick in order to determine whether Borrelia bacteria can be detected in the bite tool. To be on the safe side, the appropriate antibiotic treatment, which is to be administered for 21 days, should be started immediately. If the tick is germ-free, the antibiotic treatment can be discontinued. If the tick is no longer present or another biting insect has triggered erythema migrans, an antibody test must be carried out from the blood.