EhrlichiaEhrlichiosisEhrlichia chaffeensisDog DiseasesEhrlichia canisDogsEhrlichia ruminantiumRickettsiaceaeRickettsiaceae InfectionsAnaplasmaArachnid VectorsTicksAntibodies, BacterialAnaplasmataceaePolymerase Chain ReactionDoxycyclineRNA, Ribosomal, 16SIxodesHeartwater DiseaseSoutheastern United StatesTick-Borne DiseasesAntigens, BacterialHorse DiseasesTick InfestationsAnaplasmosisSequence Analysis, DNA