Anaplasma phagocytophilum surface proteins Asp14 and OmpA and homologous genes from Anaplasmatacaea family members are used in compositions suitable for vaccines to treat or prevent infections caused by tick-born bacteria of the Anaplasmatacaea family. Asp14 and/or OmpA proteins or peptide fragments may be used in combination with other Anaplasmatacaea surface proteins to elicit an immune response. Furthermore, antibodies to Asp14 and/or OmpA proteins can be used in diagnostic methods to determine whether an individual has contracted an Anaplasmatacaea infection. Because of the conserved invasin domains in the surface proteins, a wide range of Anaplasmatacaea infections may be diagnosed, treated or prevented using compositions of the invention.
