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Dr. Katherine Horak

Dr. Katherine Horak

Katherine Horak is a pharmacologist and toxicologist at the National Wildlife Research Center.

NWRC Research ProjectReproductive Technologies

Current Research

Dr. Horak is currently involved in the development of physiologically-based pharmacokinetic models of anticoagulant rodenticides warfarin and diphacinone for rats and quail. These models will generate approximations of rodenticide residues in various tissues and, therefore, provide a means to estimate the sensitivity of non-target species to rodenticide residues.


  • Ph.D., University of Arizona, Pharmacology and Toxicology, "CD4+ lymphocyte regulation of vascular and cardiac extracellular matrix structure and function"
  • B.S., Northern Arizona University, Mathematics
  • B.S., Northern Arizona University, Biology

Contact Information

Recent Publications


Franklin, A.B., P.C. Carlson, A. Rex, J.T. Rockweit, D.Garza, E. Culhane, S.F. Volker, R.J. Dusek, V.I. Shearn-Bochsler, M.W. Gabriel, and K.E. Horak. 2018. Grass is not always greener: rodenticide exposure of a threatened species near marijuana growing operations. BMC Research Notes 11:94. doi: 10.1186/s13104-018-3206-z

Horak, K.E., N.M. Hofmann, and B.A. Kimball. 2018. Assessments of zinc phosphide bait shyness and tools for reducing flavor aversions. Crop Protection 112:214-219. doi: 10.1016/j.cropro.2018.06.002

Horak, K.E., P.M. Fisher, and B. Hopkins. 2018. Pharmacokinetics of anticoagulant rodenticides in target and non-target organisms. pgs. 87-108. In: N.W. van den Brink, J.E. Elliott, R.F. Shore and B.A. Rattner, editors. Emerging Topics in Ecotoxicology Principles, Approaches and Perspectives Volume 5 Anticoagulant Rodenticides and Wildlife. Springer International Publishing, Cham, Switzerland, 398 pp.

Kopanke, J.H., K.E. Horak, E. Musselman, C.A. Miller, K. Bennett, C.S. Olver, S.F. Volker, S. VandeWoude, and S.N. Bevins. 2018. Effects of low-level brodifacoum exposure on the feline immune response. Scientific Reports 8(1):8168. doi: 10.1038/s41598-018-26558-3

Mathewson, P.D., K.C. Hanson-Dorr, W.P. Porter, S.J. Bursian, K.M. Dean, K. Healy, K. Horak, J.E. Link, K.E. Harr, and B.S. Dorr. 2018. Experimental and modeled thermoregulatory costs of repeated sublethal oil exposure in the Double-crested Cormorant, Phalacrocorax auritus. Marine Pollution Bulletin 135:216-223. doi: 10.1016/j.marpolbul.2018.07.003

Snow, N. P., J. A. Foster, E. H. VanNatta, K. E. Horak, S. T. Humphrys, L. D. Staples, D. G. Hewitt, and K. C. VerCauteren. 2018. Potential secondary poisoning risks to non-targets from a sodium nitrite toxic bait for invasive wild pigs. Pest Management Science 74:181–188.


Alexander, C.R., M.J. Hooper, D. Cacela, K.D. Smelker, C.S. Calvin, K.M. Dean, S.J. Bursian, F.L. Cunningham, K.C. Hanson-Dorr, K.E. Horak, J.P. Isanhart, J. Link, S.A. Shriner, and C.A.J. Godard-Codding. 2017. Reprint of: CYP1A protein expression and catalytic activity in double-crested cormorants experimentally exposed to Deepwater Horizon Mississippi Canyon 252 oil. Ecotoxicology and Environmental Safety 146:68-75. doi: 10.1016/j.ecoenv.2017.02.049

Bursian, S.J., C.R. Alexander, D. Cacela, F.L. Cunningham, K.M. Dean, B.S. Dorr, C.K. Ellis, C.A. Godard-Codding, C.G. Guglielmo, K.C. Hanson-Dorr, K.E. Harr, K.A. Healy, M.J. Hooper, K.E. Horak, J.P. Isanhart, L.V. Kennedy, J.E. Link, I. Maggini, J.K. Moye, C.R. Perez, C.A. Pritsos, S.A. Shriner, K.A. Trust, and P.L. Tuttle. 2017. Reprint of: Overview of avian toxicity studies for the Deepwater Horizon natural resource damage assessment. Ecotoxicology and Environmental Safety 146:4-10. doi: 10.1016/j.ecoenv.2017.05.014

Cunningham, F., K. Dean, K. Hanson-Dorr, K. Harr, K. Healy, K. Horak, J. Link, S. Shriner, S. Bursian, and B. Dorr. 2017. Reprint of: Development of methods for avian oil toxicity studies using the double crested cormorant (Phalacrocorax auritus). Ecotoxicology and Environmental Safety 146:19-28. doi: 10.1016/j.ecoenv.2017.03.025

Dean, K.M., D. Cacela, M.W. Carney, F.L. Cunningham, C. Ellis, A.R. Gerson, C.G. Guglielmo, K.C. Hanson-Dorr, K.E. Harr, K.A. Healy, K.E. Horak. J.P. Isanhart, L.V. Kennedy, J.E. Link. I. Lipton, A.K. McFadden, J.K. Moye, C.R. Perez, C.A. Pritsos, K.L. Pritsos, T. Muthumalage, S.A. Shriner, and S.J. Bursian. 2017. Testing of an oral dosing technique for double-crested cormorants, Phalacocorax auritus, laughing gulls, Leucophaeus atricilla, homing pigeons, Columba livia, and western sandpipers, Calidris mauri, with artificially weather MC252 oil. Ecotoxicology and Environmental Safety 146:11-18. doi: 10.1016/j.ecoenv.2017.07.003

Dean, K.M., S.J. Bursian, D. Cacela, M.W. Carney, F.L. Cunningham, B. Dorr, K.C. Hanson-Dorr, K.A. Healy, K.E. Horak, J.E. Link, I. Lipton, A.K. McFadden, M.A. McKernan, and K.E. Harr. 2017. Changes in white cell estimates and plasma chemistry measurements following oral or external dosing of double-crested cormorants, Phalacrocorax auritus, with artificially weathered MC252 oil. Ecotoxicology and Environmental Safety 146:40-51. doi: 10.1016/j.ecoenv.2017.08.007

Harr, K.E., D.R. Reavill, S.J. Bursian, D. Cacela, F.L. Cunningham, K.M. Dean, B.S. Dorr, K.C. Hanson-Dorr, K. Healy, K. Horak, J.E. Link, S. Shriner, and R.E. Schmidt. 2017. Organ weights and histopathology of double-crested cormorants (Phalacrocorax auritus) dosed orally or dermally with artificially weathered Mississippi Canyon 252 crude oil. Ecotoxicology and Environmental Safety 146:52-61. doi: 10.1016/j.ecoenv. 2017.07.011

Harr, K.E., F.L. Cunningham, C.A. Pritsos, K.L. Pritsos, T. Muthumalage, B.S. Dorr, K.E. Horak, K.C. Hanson-Dorr, K.M. Dean, D. Cadela, A.K. McFadden, J.E. Link, K.A. Healy, P. Tuttle, and S.J. Bursian. 2017. Weathered MC252 crude oil-induced anemia and abnormal erythroid morphology in double-crested cormorants (Phalacrocorax auritus) with light microscopic and ultrastructural description of Heinz bodies. Ecotoxicology and Environmental Safety 146:29-39. doi: 10.1016/j.econv. 2017.07.030

Harr, K.E., M. Rishniw, T.L. Rupp, D. Cacela, K.M. Dean, B.S. Dorr, K.C. Hanson-Dorr, K. Healy, K. Horak, J.E. Link, D. Reavill, S.J. Bursian, and F.L. Cunningham. 2017. Dermal exposure to weathered MC252 crude oil results in echocardiographically identifiable systolic myocardial dysfunction in double-crested cormorants (Phalacrocorax auritus). Ecotoxicology and Environmental Safety 146:76-82. doi: 10.1016/j.ecoenv.2017.04.010

Horak, K.E., S.J. Bursian, C.K. Ellis, K.M. Dean, J.E. Link, K.C. Hanson-Dorr, F.L. Cunningham, K.E. Harr, C.A. Pritsos, K.L. Pritsos, K.A. Healy, D. Cacela, and S.A. Shriner. 2017. Toxic effects of orally ingested oil from the Deepwater Horizon spill on laughing gulls. Ecotoxicology and Environmental Safety. Online. doi: 10.1016/j.ecoenv.2017.07.018

Pritsos, K.L., C.R. Perez, T. Muthumalage, K.M. Dean, D. Cacela, K. Hanson-Dorr, F. Cunningham, S.J. Bursian, J.E. Link, S. Shriner, K. Horak, and C.A. Pritsos. 2017. Dietary intake of Deepwater Horizon oil-injected live food fish by double-crested cormorants resulted in oxidative stress. Ecotoxicology and Environmental Safety 146:62-67. doi: 10.1016/j.ecoenv.2017.06.067


Patton, T.G., S.L. Blamer, and K.E. Horak. 2016. Detecting methemoglobinemia in animals with a drop of blood.  Plos one 11(12):e0167942.  doi:10.1371/journal.pone.0167942


Rattner, B.A., K.E. Horak, R.S. Lazarus, S.L. Schultz, S. Knowles, B.G. Abbo, and S.F. Volker. 2015.Toxicity reference values for chlorophacinone and their application for assessing anticoagulant rodenticide risk to raptors. Ecotoxicology 24:720-734.  doi: 10.1007/s10646-015-1418-8.

Horak, K.E., S.F. Volker, and C.M. Campton. 2015. Increased diphacinone and chlorophacinone metabolism in previously exposed wild caught voles, Microtus californicus. Crop Protection 7:35-39.  doi: 10.1016/j.cropro.2015.08.011


Rattner, B.A., R.S. Lazarus, S.L. Schultz, K.E. Horak, B.G. Abbo, and S.F. Volker. 2014. Development of dietary-based toxicity reference values to assess the risk of chlorophacinone to non-target raptorial birds. Proceedings of the 26th Vertebrate Pest Conference 26:347-352.  

Horak, K., R. Chipman, L. Murphy, and J. Johnston. 2014. Environmental contaminant concentrations in Canada Goose (Branta canadensis) muscle: Probabilistic risk assessment for human consumers. Journal of Food Protection 77(9):1634-1641. doi: 10.4315/0362-028X.JFP-13-364.

Rattner, B.A., K.E. Horak, R.S. Lazarus, D.A. Goldade, and J.J. Johnston. 2014. Toxicokinetics and coagulopathy threshold of the rodenticide diphacinone in Eastern screech-owls (Megascops asio). Environmental Toxicology and Chemistry 33(1): 74-81. doi: 10.1002/etc.2390.


Rattner B.A., Horak K.E., Warner S.E., Day D.D., Meteyer C.U., Volker S.F., Eisemann J.D., Johnston J.J. 2011. Acute Toxicity, Histopathology, and Coagulopathy in American Kestrels (Falco Sparverius) following administration of the Rodenticide Diphacinone. Environmental Toxicology and Chemistry 30:1213-1222. DOI: 10.1002/etc.490.


Horak, K. E., C. R. Wermager, and T. M. Primus. 2010. The use of liver microsome in-vitro methods to study toxicant metabolism and predict species efficacy. Proceedings of the Vertebrate Pest Conference 24:195-198. 324K

Rattner B.A., Horak K.E., Lazarus R.S., Eisenreich K.M., Meteyer C.U., Volker S.F., Campton C.M., Eisemann J.D., Johnston J.J. 2012. Assessment of toxicity and potential risk of the anticoagulant rodenticide diphacinone using Eastern screech-owls (Megascops asio). Ecotoxicology 21:832-846.

Rattner B.A., Horak K.E., Warner S.E., Day D.D., Johnston J.J. 2010. Comparative toxicity of diphacinone to northern bobwhite ( Colinus virginianus ) and American kestrels ( Falco sparverius ). Proceedings of the Vertebrate Pest Conference 24:146-152.

Rattner B.A., Horak K.E., Warner S.E., Johnston J.J. 2010. Acute toxicity of diphacinone in Northern bobwhite: Effects on survival and blood clotting. Ecotoxicology and Environmental Safety 73:1159-1164.


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