Deer keds are blood-feeding flies from which several human and animal pathogens have been detected, including the causative agent of Lyme Disease (Borrelia burgdorferi). Cervids, which are the primary hosts of deer keds, are not natural reservoirs of B. burgdorferi, and it has been suggested that deer keds may acquire bacterial pathogens by co-feeding near ticks that are infected with the bacteria. We tested this hypothesis by using a molecular assay to screen for presence of Anaplasma spp., Bartonella spp., Borrelia spp., and Rickettsia spp. in specimens of European deer keds (n=306) and blacklegged ticks (n=315) collected from 38 individual white-tailed deer in Pennsylvania. There was limited similarity in the bacterial DNA detected between these ectoparasites per host, suggesting that co-feeding may not be a mechanism by which deer keds acquire these bacteria. We discuss these results in relation to deer ked feeding biology, life history, and collection timepoints. In addition, we screened specimens of European deer keds (n=410), Neotropical deer keds (n=13), Western American deer keds (n=10), and Pacific deer keds (n=14) for these same bacterial pathogens. Resources in this dataset:Resource Title: Borrelia spp. flaB from Ixodes scapularis. File Name: Borrelia_flaB_Iscapularis_Olafsonetal.csvResource Description: A PCR assay targeting Borrelia spp. flagellin (flaB, 650 bp; (Barbour et al. 1996)) was used to detect presence of this bacterium in DNAs isolated from field-collected samples. Barbour, A. G., G. O. Maupin, G. J. Teltow, C. J. Carter, and J. Piesman. 1996. Identification of an uncultivable Borrelia species in the hard tick Amblyomma americanum: possible agent of a Lyme disease-like illness. J Infect Dis 173: 403-409Resource Title: Bartonella ribC from Lipoptena spp and Neolipoptena ferrisi. File Name: Bartonella_ribC_DeerKed_Olafsonetal_2.csvResource Description: A PCR assay targeting Bartonella spp. riboflavin synthase (ribC, 575 bp; (Johnson et al. 2003) was used to detect presence of this bacterium in DNAs isolated from field-collected deer ked samples. Johnson, G., M. Ayers, S. C. McClure, S. E. Richardson, and R. Tellier. 2003. Detection and identification of Bartonella species pathogenic for humans by PCR amplification targeting the riboflavin synthase gene (ribC). J Clin Microbiol 41: 1069-1072. Resource Title: Rickettsia spp. sca0 from Lipoptena cervi and Ixodes scapularis. File Name: Rickettsia_sca0_DeerKed-Iscap_Olafsonetal_1.csvResource Description: A PCR assay targeting Rickettsia sp. surface cell antigen, sca0 (rompA, 525 bp; (Regnery et al. 1991)) was used to detect presence of this bacterium in DNAs isolated from field-collected samples. Regnery, R. L., C. L. Spruill, and B. D. Plikaytis. 1991. Genotypic identification of rickettsiae and estimation of intraspecies sequence divergence for portions of two rickettsial genes. J Bacteriol 173: 1576-1589. Resource Title: Anaplasma spp. groEL from Lipoptena cervi and Ixodes scapularis. File Name: Anaplasma_groEL_Lcervi-Iscap_Olafson_0.csvResource Description: A PCR assay targeting the Anaplasmataceae family heat shock protein (groEL, 350 bp; (Tabara et al. 2007), was used to detect presence of this bacterium in DNAs isolated from field-collected samples. Tabara, K., S. Arai, T. Kawabuchi, A. Itagaki, C. Ishihara, H. Satoh, N. Okabe, and M. Tsuji. 2007. Molecular survey of Babesia microti, Ehrlichia species and Candidatus Neoehrlichia mikurensis in wild rodents from Shimane Prefecture, Japan. Microbiol Immunol 51: 359-367