Epidemiological, Clinical and Biological Characteristics of Human Anaplasmosis Cases in Alsace: a Retrospective and Multicenter Study

Anaplasmosis is a bacterial infection caused by the intracellular bacterium Anaplasma phagocytophilum and transmitted by ticks. This bacterium is present in approximately 1% of ticks in Alsace. This infection is responsible for clinical manifestations that are most often mild, including fever, headache, and myalgia, occurring 2 to 3 weeks after a tick bite. However, this infection can be accompanied by potentially serious or even fatal complications, including severe cytopenias, acute respiratory distress syndrome, septic shock, severe neurological disorders, hemorrhagic manifestations, macrophage activation syndrome, and multiple organ failure. Mortality is variable and appears to be higher in American studies, where it is around 4%. Treatment is well-established and relies on doxycycline, which is highly effective. Although a few cases have been described in France, these are mostly isolated cases or short series of cases, whereas Belgium, Poland, and Slovenia have reported numerous cases. Thus, there is a lack of data on French cases, and given that Alsace is in a region with a high prevalence of tick-borne diseases, data is needed to better understand the epidemiology and to better identify suspected cases in order to provide appropriate care.