C6 and infection: This is surprising, as a lower seroprevalence was also expected for B. burgdorferi s.l. One reason might be the use of different methodologies for the detection of antibodies against B. burgdorferi s.l. For example, the IDEXX SNAP 4dx test uses the C6 antigen, which is part of the highly specific VlsE antigen expressed by B. burgdorferi s.l. during host infection [51].