Provided herein are immunoreactive peptides which can selectively bind Ehrlichia-specific anti-p120 or anti-p140 antibodies. Methods and kits utilizing the immunoreactive peptides are also provided. The immunoreactive peptides may be utilized, e.g., for determining whether or not a subject is infected with Ehrlichia chaffeensis or Ehrlichia canis. In certain embodiments, the immunoreactive peptides may be utilized in an ELISA or lateral flow assay.