Described herein are improved diagnostic tools for veterinary and human use which can be used for serodiagnosing A. platys in mammals, particularly in members of the Canidae family and in humans. The diagnostic tools are a group of outer membrane proteins of A. platys and variants thereof, referred to hereinafter as the “OMP proteins”, a group of outer membrane proteins of A. platys and variants thereof referred to hereinafter as the “P44 proteins”, and antibodies to the OMP proteins and the P44 proteins.
