Daniel A Grear
Dan Grear is a Wildlife Disease Ecologist at the National Wildlife Health Center.
I am interested in mechanisms that cause heterogeneities in pathogen transmission in wild animal disease systems and at the interface of wildlife, domestic animal, and human health. I lead investigations into wildlife mortality events and research that incorporates field studies with theoretical modeling of disease systems to identify key mechanisms that drive transmission dynamic.
Professional Experience
2015 - Present Wildlife Disease Ecologist, U.S. Geological Survey, National Wildlife Health Center, Madison, WI
2013 - 2015 Ecologist, U.S. Department of Agriculture, Veterinary Services, Center for Epidemiology and Animal Health, Fort Collins, CO
2011 - 2014 Post-Doctoral Researcher, Colorado State University
Education and Certifications
2011 Ph.D. Ecology, Pennsylvania State University
2006 M.S. Wildlife Ecology, University of Wisconsin
2002 B.S. Wildlife Ecology, University of Wisconsin
Affiliations and Memberships*
Member of the Ecological Society of America
Member of the Wildlife Society
Bsal Task Force Working Group Member
Science and Products
Batrachochytrium salamandrivorans (Bsal) not detected in an intensive survey of wild North American amphibians
Avian influenza virus prevalence in marine birds is dependent on ocean temperatures
The ecology of chronic wasting disease in wildlife
Quarterly wildlife mortality report April 2019
Mortality due to Tyzzer's disease of muskrats in northern Ohio, USA
Pathology and case definition of Severe Perkinsea Infections of frogs
Identifying management-relevant research priorities for responding to disease-associated amphibian declines
Chlamydia psittaci in feral Rosy-faced Lovebirds (Agapornis roseicollis) and other backyard birds in Maricopa County, Arizona
Quarterly wildlife mortality report January 2018
Inferring epidemiologic dynamics from viral evolution: 2014–2015 Eurasian/North American highly pathogenic avian influenza viruses exceed transmission threshold, R0 = 1, in wild birds and poultry in North America
Novel dermatophilosis and concurrent amyloidosis in Sanderlings (Calidris alba) from Louisiana, USA
Pathogenic lineage of Perkinsea associated with mass mortality of frogs across the United States
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
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Filter Total Items: 37
Batrachochytrium salamandrivorans (Bsal) not detected in an intensive survey of wild North American amphibians
The salamander chytrid fungus (Batrachochytrium salamandrivorans [Bsal]) is causing massive mortality of salamanders in Europe. The potential for spread via international trade into North America and the high diversity of salamanders has catalyzed concern about Bsal in the U.S. Surveillance programs for invading pathogens must initially meet challenges that include low rates of occurrence on the lAuthorsHardin Waddle, Daniel A. Grear, Brittany Mosher, Evan H. Campbell Grant, Michael J. Adams, Adam R. Backlin, William Barichivich, Adrianne B. Brand, Gary M. Bucciarelli, Daniel L. Calhoun, Tara Chestnut, Jon M. Davenport, Andrew E. Dietrich, Robert N. Fisher, Brad Glorioso, Brian J. Halstead, Marc P Hayes, R. Ken Honeycutt, Blake R. Hossack, Patrick M. Kleeman, Julio A. Lemos-Espinal, Jeffrey M. Lorch, Robert W. Atkinson, Erin L. Muths, Christopher Pearl, Katherine Richgels, Charles W Robinson, Mark F. Roth, Jennifer Rowe, Walter Sadinski, Brent H. Sigafus, Iga Stasiak, Samuel Sweet, Susan C. Walls, Gregory J Watkins-Colwell, C. LeAnn White, Lori A Williams, Megan E. WinzelerAvian influenza virus prevalence in marine birds is dependent on ocean temperatures
Waterfowl and shorebirds are the primary hosts of influenza A virus (IAV), however, in most surveillance efforts, large populations of birds are not routinely examined; specifically marine ducks and other birds that reside predominately on or near the ocean. We conducted a long-term study sampling sea ducks and gulls in coastal Maine for IAV and found a virus prevalence (1.7%) much lower than is tAuthorsJeffrey S. Hall, Robert J. Dusek, Sean Nashold, Joshua L. TeSlaa, Bradford R. Allen, Daniel A. GrearThe ecology of chronic wasting disease in wildlife
Prions are misfolded infectious proteins responsible for a group of fatal neurodegenerative diseases termed transmissible spongiform encephalopathy or prion diseases. Chronic Wasting Disease (CWD) is the prion disease with the highest spillover potential, affecting at least seven Cervidae (deer) species. The zoonotic potential of CWD is inconclusive and cannot be ruled out. A risk of infection forAuthorsLuis E. Escobar, Sandra Pritzkow, Steven N Winter, Daniel A. Grear, Megan S. Kirchgessner, Ernesto Dominguez-Villegas, Gustavo Machado, A Townsend Peterson, Claudio SotoQuarterly wildlife mortality report April 2019
No abstract available.AuthorsBryan J. Richards, Daniel A. Grear, C. LeAnn White, Thierry M. Work, Emily A UnderwoodMortality due to Tyzzer's disease of muskrats in northern Ohio, USA
In 2017, we investigated a mortality event of muskrat (Ondatra zibethicus) in Northwest Ohio, USA, and determined the causes of death to be from Tyzzer's disease due to Clostridium piliforme and Klebsiella pneumoniae septicemia. The gross presentation resembled tularemia, which highlighted the importance of a complete diagnostic investigation.AuthorsDaniel A. Grear, Julia S. Lankton, Sara Zaleski, Mark Witt, Jeffrey M. LorchPathology and case definition of Severe Perkinsea Infections of frogs
Severe Perkinsea infection (SPI) is an emerging disease of frogs responsible for mass mortalities of tadpoles across the United States. It is caused by protozoa belonging to the phylum Perkinsozoa that form a distinct group referred to as the Pathogenic Perkinsea Clade of frogs. In this work, we provide detailed description of gross and histologic lesions from 178 naturally infected tadpoles, inclAuthorsMarcos Isidoro Ayza, Daniel A. Grear, Aurélie ChambouvetIdentifying management-relevant research priorities for responding to disease-associated amphibian declines
A research priority can be defined as a knowledge gap that, if resolved, identifies the optimal course of conservation action. We (a group of geographically distributed and multidisciplinary research scientists) used tools from nominal group theory and decision analysis to collaboratively identify and prioritize information needs within the context of disease-associated amphibian decline, in orderAuthorsEvan H. Campbell Grant, M. J. Adams, Robert N. Fisher, Daniel A. Grear, Brian J. Halstead, Blake R. Hossack, Erin L. Muths, Katherine L. D. Richgels, Robin E. Russell, Kelly L. Smalling, J. Hardin Waddle, Susan C. Walls, C. LeAnn WhiteByEcosystems Mission Area, Water Resources Mission Area, Biological Threats and Invasive Species Research Program, Species Management Research Program, Eastern Ecological Science Center, Forest and Rangeland Ecosystem Science Center, Fort Collins Science Center, National Wildlife Health Center, New Jersey Water Science Center, Northern Rocky Mountain Science Center, Western Ecological Research Center (WERC), Wetland and Aquatic Research CenterChlamydia psittaci in feral Rosy-faced Lovebirds (Agapornis roseicollis) and other backyard birds in Maricopa County, Arizona
In 2013, a mortality event of nonnative, feral Rosy-faced Lovebirds (Agapornis roseicollis) in residential backyards in Maricopa County, Arizona, US was attributed to infection with Chlamydia psittaci. In June 2014, additional mortality occurred in the same region. Accordingly, in August 2014 we sampled live lovebirds and sympatric bird species visiting backyard bird feeders to determine the prevaAuthorsRobert J. Dusek, Anne Justice-Allen, Barbara Bodenstein, Susan Knowles, Daniel A. Grear, Laura Adams, Craig Levy, Haley D. Yaglom, Valerie I. Shearn-Bochsler, Paula Ciembor, Christopher R. Gregory, Denise Pesti, Branson W. RitchieQuarterly wildlife mortality report January 2018
No abstract available.AuthorsBryan J. Richards, Daniel A. Grear, Anne Ballmann, Robert J. Dusek, Robert Kaler, Kathy KuletzInferring epidemiologic dynamics from viral evolution: 2014–2015 Eurasian/North American highly pathogenic avian influenza viruses exceed transmission threshold, R0 = 1, in wild birds and poultry in North America
Highly pathogenic avian influenza virus (HPAIV) is a multihost pathogen with lineages that pose health risks for domestic birds, wild birds, and humans. One mechanism of intercontinental HPAIV spread is through wild bird reservoirs, and wild birds were the likely sources of a Eurasian (EA) lineage HPAIV into North America in 2014. The introduction resulted in several reassortment events with NorthAuthorsDaniel R. Grear, Jeffrey S. Hall, Robert J. Dusek, Hon S. IpNovel dermatophilosis and concurrent amyloidosis in Sanderlings (Calidris alba) from Louisiana, USA
We observed Sanderlings (Calidris alba) with facial growths in coastal Louisiana, US during summer of 2016. Severe lesions were associated with lethargy and lack of a flight response. We determined that the skin growth etiology was a bacterium of the genus Dermatophilus, rarely reported infecting birds. Sanderlings also exhibited severe amyloidosis.AuthorsValerie I. Shearn-Bochsler, Jessica L. Schulz, Robert C. Dobbs, Jeffrey M. Lorch, J. Hardin Waddle, Daniel A. GrearPathogenic lineage of Perkinsea associated with mass mortality of frogs across the United States
Emerging infectious diseases such as chytridiomycosis and ranavirus infections are important contributors to the worldwide decline of amphibian populations. We reviewed data on 247 anuran mortality events in 43 States of the United States from 1999–2015. Our findings suggest that a severe infectious disease of tadpoles caused by a protist belonging to the phylum Perkinsea might represent the thirdAuthorsMarcos Isidoro Ayza, Jeffrey M. Lorch, Daniel A. Grear, Megan Winzeler, Daniel L. Calhoun, William J. BarichivichNon-USGS Publications**
Gorsich EE, Luis AD, Buhnerkempe MG, Grear DA, Portacci K, Miller RS, Webb CT. 2016. Mapping US cattle shipment networks: Spatial and temporal patterns of trade communities from 2009 to 2011. Preventive Veterinary Medicine, 134, 82-91.Lavelle MJ, Kay SL, Pepin KM, Grear DA, Campa H, VerCauteren K. 2016. Evaluating wildlife-cattle contact rates to improve the understanding of dynamics of bovine tuberculosis transmission in Michigan, USA. Preventive Veterinary Medicine, 135, 28-36.Scott A, B McCluskey, M Brown-Reid, DA Grear, P Pitcher, G Ramos, D Spencer. 2016. Porcine epidemic diarrhea virus introduction into the United States: Root cause investigation. Preventive Veterinary Medicine, 123, 192-201. doi: 10.1016/j.prevetmed.2015.11.013Glaser L, M Carstensen, S Shaw, S Robbe-Austerman, A Wunschmann, DA Grear, T Stuber, B Thomsen. 2016. Descpriptive epidemiology and whole genome sequencing analysis for an outbreak of bovine tuberculosis in beef cattle and white-tailed deer in Northwestern Minnesota. PLoS ONE, e0145735.McClure RSM, CL Burdett, ML Farnsworth, MW Lutman, DM Theobold, PD Riggs, DA Grear, RS Miller. 2015. Modeling and mapping the probability of occurrence of invasive wild pigs across the contiguous United States. PLoS ONE 10(8): e0133771. doi:10.1371/journal.pone.0133771Pepin KM, CB Leach, C Marques-Toledo, KH Laass, KS Paixao, AD Luis, DTS Hayman, NG Johnson, MG Buhnerkempe, S Carver, DA Grear, K Tsao, AE Eiras, and CT Webb. 2015. Utility of mosquito surveillance data for spatial prioritization of vector control against dengue viruses in three Brazilian cities. Parasites and Vectors, 8, 98.Tsao K, S Robbe-Austerman, RS Miller, K Portacci, DA Grear, and CT Webb. 2014. Sources of bovine tuberculosis in the United States. Infection, Genetics, and Evolution. 114, 201-212.Luong LT, DA Grear, and PJ Hudson. 2014. Manipulation of host-resource dynamics impacts transmission of trophically transmitted parasites. International Journal for Parasitology, 44, 737-742.Grear DA, J Kaneene, J Averill, and CT Webb. 2014. Local cattle movements in response to ongoing bovine TB zonation and regulations. Preventive Veterinary Medicine, 114, 201-212.Buhnerkempe MG, MJ Tildesley, T Lindström, DA Grear, RS Miller, K Portacci, M Keeling, U Wennergren, and CT Webb. 2014. The impact of movements and animal density on continental scale cattle disease outbreaks in the United States. PLoS one, e91724.Grear DA, LT Luong, and PJ Hudson. 2013. Network transmission inference: host behavior and parasite life-cycle make social networks meaningful in disease ecology, Ecological Applications, 23, 1906-1914.Buhnerkempe, MG, DA Grear, RS Miller, K Portacci, J Lombard, and CT Webb. 2013. A national-scale picture of U.S. cattle movements obtained from Interstate Certificates of Veterinary Inspection data. Prev. Vet. Med., 112, 318-329.Lindström T, DA Grear, MG Buhnerkempe, CT Webb, RS Miller, K Portacci, and U Wennergren. 2013. Bayesian approach for modeling cattle movements in the United States: scaling up a partially observed network. PLoS ONE,8, e53432. doi:10.1371/journal.pone.0053432Grear DA, LT Luong, and PJ Hudson. 2012. Sex-biased transmission of a complex life-cycle parasite: why males matter. Oikos, 121, 1446-1453. doi: 10.1111/j.1600-0706.2012.20358.xBlanchong, JA, DA Grear, BV Weckworth, DP Keane, KT Scribner, and MD Samuel. 2012. Effects of chronic wasting disease on reproduction and fawn harvest vulnerability in Wisconsin white-tailed deer. Journal of Wildlife Diseases, 48, 361-370.Rogers K, S Robinson, MD Samuel, and DA Grear. 2011. Diversity and distribution of white-tailed deer mtDNA lineages in CWD outbreak areas in southern Wisconsin, USA. Journal of Toxicology and Environmental Health, 74, 1521-1535. doi: 10.1080/15287394.2011.618980Grear DA and PJ Hudson. 2011. The dynamics of macroparasite host-self-infection: a study of the patterns and processes of pinworm (Oxyuridae) aggregation. Parasitology, 138, 619-617. doi: 10.1017/S0031182011000096.Grear DA, MD Samuel, K Scribner, BV Weckworth, and JA Langenberg. 2010. Influence of genetic relatedness and spatial proximity on CWD transmission among female white-tailed deer. Journal of Applied Ecology, 47, 532-540.Luong, LT, SE Perkins, DA Grear, A Rizzoli, and PJ Hudson. 2010. The relative importance of host characteristics and co-infection in generating variation in Heligmosomoides polygyrus fecundity. Parasitology, 137, 1003-1012.Grear DA, SE Perkins, and PJ Hudson. 2009. Does elevated testosterone result in increased exposure and transmission of parasites? Ecology Letters, 12, 528-537.Luong, LT, DA Grear, and PJ Hudson. 2009. Male hosts are responsible for the transmission of a trophically transmitted parasite, Pterygodermatites peromysci to the intermediate host in the absence of sex-biased infection. International Journal for Parasitology, 39, 1263-1268.Grear DA, MD Samuel, JA Langenberg, and D Keane. 2006. Demographic patterns and harvest vulnerability of chronic wasting disease infected white-tailed deer in Wisconsin. Journal of Wildlife Management, 70, 546-553.**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
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*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government