Rickettsia are zoonotic obligate intracellular bacteria of the family Rickettsiaceae. They are associated with arthropods, primarily ticks, but also fleas, body lice and mites, which serve as the main reservoir. These arthropods also serve as vectors of rickettsiosis while feeding on both humans and animals.
The antibody response to infections by these agents is primarily directed against lipopolysaccharide (LPS) and 1-2 outer-membrane proteins (OmpA and/or OmpB). The standard IFA and MIF methods detect antibody against the whole organism and remain the most commonly used diagnostic methods. ELISA methods are also currently available which focus upon more specific reactivities to the LPS antigens (IgG screening) and OmpB protein antigens (IgG/IgM).