Ehrlichiosis, or correctly human granulocytic anaplasmosis, is caused by Anaplasma phagocytophylum (formerly Ehrlichia phagocytophylum - hence the name ehrlichiosis). Anaplasma is transmitted to humans during sucking of the tick and attacks the white blood cells in which they multiply. This reduces their function in the defense of the body. The disease occurs predominantly in the US, in Europe is diagnosed only sporadically, probably because of its non-specific symptoms.

The disease breaks out 7-10 days after the tick has been attached. As already mentioned, ehrlichiosis has very nonspecific symptoms and is therefore difficult to diagnose. These are headache, muscle pain and fatigue. Other symptoms include rash (similar to Erythema migrans - in about 20% of cases), enlarged nodules and fever. By destroying the body's immunity, it promotes the growth of other infections present in the body. It is not usually dangerous for a healthy person. Although it is reported to be fatal in 3% of cases, these deaths are mostly in the category of immunocompromised people. Ehrlichiosis is well treatable especially in the early stages. Doxycycline, tetracycline, minocycline or rifampin are used for the treatment.