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Journal of Medical Entomology logoLink to Journal of Medical Entomology
. 2021 Jan 6;58(3):1219–1233. doi: 10.1093/jme/tjaa283

Reported County-Level Distribution of Lyme Disease Spirochetes, Borrelia burgdorferi sensu stricto and Borrelia mayonii (Spirochaetales: Spirochaetaceae), in Host-Seeking Ixodes scapularis and Ixodes pacificus Ticks (Acari: Ixodidae) in the Contiguous United States

Amy C Fleshman 1, Christine B Graham 1, Sarah E Maes 1, Erik Foster 1, Rebecca J Eisen 1,✉
Editor: Maria Diuk-Wasser
PMCID: PMC8355468  PMID: 33600574

Abstract

Lyme disease is the most common vector-borne disease in the United States. While Lyme disease vectors are widespread, high incidence states are concentrated in the Northeast, North Central and Mid-Atlantic regions. Mapping the distribution of Lyme disease spirochetes in ticks may aid in providing data-driven explanations of epidemiological trends and recommendations for targeting prevention strategies to communities at risk. We compiled data from the literature, publicly available tickborne pathogen surveillance databases, and internal CDC pathogen testing databases to map the county-level distribution of Lyme disease spirochetes reported in host-seeking Ixodes pacificus and Ixodes scapularis across the contiguous United States. We report B. burgdorferi s.s.-infected I. scapularis from 384 counties spanning 26 eastern states located primarily in the North Central, Northeastern, and Mid-Atlantic regions, and in I. pacificus from 20 counties spanning 2 western states, with most records reported from northern and north-coastal California. Borrelia mayonii was reported in I. scapularis in 10 counties in Minnesota and Wisconsin in the North Central United States, where records of B. burgdorferi s.s. were also reported. In comparison to a broad distribution of vector ticks, the resulting map shows a more limited distribution of Lyme disease spirochetes.

Keywords: tickborne disease, tickborne surveillance, host-seeking tick, acarological risk, pathogen distribution

The public health burden of tickborne diseases has been steadily increasing in the United States since the 1990s. This increase resulted, in part, from geographical expansion of medically important ticks and tickborne pathogens and improved detection and diagnostic methods that led to the discovery of new tickborne pathogens (Tijsse-Klasen et al. 2014, Eisen et al. 2017, Rosenberg et al. 2018). Among tickborne diseases reported in the United States, Lyme disease, caused by Borrelia burgdorferi sensu stricto (s.s.) and less commonly and more focally by Borrelia mayonii, is the most common vector-borne disease with over 30,000 cases reported annually (Adams et al. 2016). The majority of Lyme disease cases are concentrated in 14 states in the North Central, Northeast and Mid-Atlantic regions (Schwartz et al. 2017). Since the mid-1990s, the number of U.S. counties meeting study-specific criteria to be classified as high incidence has increased by nearly 300% (Kugeler et al. 2015). Over a similar time period, the number of counties in which the primary vector of Lyme disease spirochetes, Ixodes scapularis, has been documented as established has more than doubled (Eisen et al. 2016).

Information on the distribution and abundance of host-seeking ticks and on the presence and prevalence of human pathogens within them can indicate where persons are at risk for exposure to tickborne pathogens and help explain epidemiological trends (Eisen and Paddock 2020). Recent tick surveillance efforts have increased our understanding of the distributions of the Lyme disease vectors in the United States, I. scapularis in the East and Ixodes pacificus in the West (Eisen et al. 2016, 2017; Eisen and Eisen 2018). However, reports showing where B. burgdorferi s.s. and B. mayonii have been identified in host-seeking Ixodes ticks across multiple U.S. regions are limited.

When the Lyme disease vaccine was licensed in the 1990s, public health officials sought to assess who should be vaccinated. In the absence of data on the distribution of infected ticks and limited data on human infections, the range of Lyme disease spirochetes was mapped using a proxy measure that was based on estimates of the proportion of reservoir hosts (rodents) relative to refractory hosts (lizards) (CDC 1999). Later, to better gauge acarological risk, a single study employed a systematic collection method across the eastern United States to document the distribution of host-seeking B. burgdorferi s.s.-infected I. scapularis nymphs (Diuk-Wasser et al. 2012). While informative, the number of counties surveyed was limited, and the ranges of ticks and spirochetes have likely expanded in the ensuing decade and a half, necessitating an update of Lyme disease spirochete distributions.

Here, we summarize data collated from a literature review, internal Centers for Disease Control and Prevention (CDC) pathogen testing databases, and publicly available tick-borne pathogen surveillance databases in maps detailing B. burgdorferi s.s. and B. mayonii presence in host-seeking I. scapularis or I. pacificus ticks at the county level in the contiguous United States. We narrowed our search to include only host-seeking ticks, because ticks in this state are most likely to bite humans, and because host-seeking ticks provide enhanced spatial precision compared to ticks collected from mobile hosts (Falco and Fish 1988, Mather et al. 1996, Eisen and Paddock 2020). This summary represents the most comprehensive assessment of the county level distribution of Lyme disease spirochetes detected in vector ticks in the United States to date.

Materials and Methods

County records from host-seeking B. burgdorferi s.s. and B. mayonii-infected I. scapularis and I. pacificus collected from 2004 to 2019 were obtained from the ArboNET Tick Module (a data portal for public health agencies to report tick and pathogen surveillance data to CDC) and an internal CDC database containing tick testing results from CDC field studies and from ticks submitted to CDC for testing by public health and university partners. The majority of ticks submitted to CDC were tested for pathogens using a series of real-time polymerase chain reaction (PCR) assays as described previously (Graham et al. 2018). All CDC testing protocols were sufficiently specific to identify and differentiate B. burgdorferi s.s. and B. mayonii; and all entities who submitted testing results to ArboNET affirmed that their testing methods also met these criteria. To acquire additional county records, we conducted several independent literature searches using the Scopus database and combinations of the search terms ‘Borrelia burgdorferi sensu stricto’, ‘Borrelia burgdorferi’, ‘Borrelia mayonii’, ‘Ixodes scapularis’, ‘Ixodes pacificus’, ‘Ixodes’, ‘host-seeking’, ‘questing’, ‘tick’, and ‘infection’, to identify articles published from 2000 to April 2020. Among all records compiled based on these search criteria, references were included if they 1) focused on host-seeking I. scapularis or I. pacificus ticks collected in the United States, 2) reported the county from which ticks were collected, 3) used pathogen detection methods adequately specific to identify B. burgdorferi s. s. and B. mayonii, and 4) provided pathogen data for counties that were not included in the internal databases described above. We obtained additional data meeting the aforementioned criteria from tickborne pathogen surveillance archives publicly available through health department websites for states where I. scapularis or I. pacificus are known to have established populations.

To effectively target host-seeking ticks, we restricted inclusion to studies that collected ticks by flagging, dragging, or CO2 traps. Ticks collected from humans, wildlife, livestock, and pets were excluded, because we could not confirm the county of exposure (CDC 2020, Eisen and Paddock 2020). If the county of collection was not included, the study was excluded. We focused on the county spatial scale for congruity with national human tickborne disease case reporting and with previous efforts to report the distributions of medically important ticks in the United States (Dennis et al. 1998, Springer et al. 2014, Kugeler et al. 2015, Eisen et al. 2016, Lehane et al. 2020). We attempted to contact authors of reports found in literature searches that met study inclusion criteria but did not report tick-borne pathogen infection data at the county level. When provided, county-level pathogen infection data from these sources were included herein.

The Borrelia burgdorferi sensu lato (s.l.) complex contains 22 genospecies, and while 9 are named species circulating in the United States, only 2 species, B. burgdorferi s. s. and B. mayonii, are culture-confirmed human pathogens in the United States (Marconi et al. 1995; Postic et al. 1998, 2007; Rudenko et al. 2009, 2011a, 2011b; Margos et al. 2010, 2016; Mead 2015; Pritt et al. 2016). Including data for ticks that were positive for other B. burgdorferi s.l. species could lead to overestimation of the geographic distribution of Lyme disease spirochetes. Therefore, we only included data from sources that utilized detection methods capable of differentiating pathogenic B. burgdorferi s.s. and B. mayonii from other B. burgdorferi s.l. species and publications in which authors described their methods as species-specific. When investigators did not identify their pathogen testing methods as B. burgdorferi s.s.-specific but did report PCR primer sequences, real-time PCR primer and probe sequences, and/or sequencing primer sequences, we used BLAST (Altschul et al. 1990) to assess target specificity. We included articles that confirmed pathogen infection results via genomic sequencing in our analyses, but we excluded those that neither specified the use of species-specific detection methods nor confirmed pathogen testing results via sequencing. Neither immunofluorescence nor microscopy allows for sufficient differentiation of B. burgdorferi s.l. species (Padgett and Bonilla 2011, Rose et al. 2019), and articles that relied exclusively on these methods were therefore excluded. Because many B. burgdorferi s.l. species have been recently identified or differentiated (Marconi et al. 1995; Postic et al. 1998, 2007; Rudenko et al. 2009, 2011a, 2011b; Margos et al. 2010, 2016; Mead 2015; Pritt et al. 2016), we limited our focus to papers published since 2000, as recent studies were more likely to accurately differentiate B. burgdorferi s.l. species.

We considered a tick-borne pathogen present in a county if any source meeting our inclusion criteria reported B. burgdorferi s.s. or B. mayonii in one or more host-seeking I. scapularis or I. pacificus ticks from that county. Pathogen presence data were mapped in ArcMap 10.5 (ESRI, Redlands, CA), where counties with B. burgdorferi s.s. or B. mayonii-positive ticks were joined on Five-digit Federal Information Processing Standard (FIPS) codes with a county-level map of the contiguous United States.

Results

Our Scopus search yielded a total of 2,123 records, of which 55 unique records met all of our inclusion criteria (Table 1). Combining all data sources, we show that the reported distribution of Lyme disease spirochetes (B. burgdorferi s.s. or B. mayonii) is more limited than the previously reported distribution of Lyme disease vectors, I. scapularis and I. pacificus (Fig. 1). We report B. burgdorferi s.s.-infected I. scapularis from 384 counties spanning 26 eastern states and Washington, D.C. Most states with counties where B. burgdorferi s.s. was present were in the North Central, Northeastern, and Mid-Atlantic regions (Table 1, Fig. 1). Borrelia mayonii was reported in I. scapularis in 10 counties in Minnesota and Wisconsin in the North Central United States. Each of the counties from which B. mayonii was reported also had records of B. burgdorferi s.s.

Table 1.

Counties where Borrelia burgdorferi s.s. or Borrelia mayonii were detected in host-seeking I. scapularis or I. pacificus.

State and county B. burgdorferi sensu stricto presence source B. mayonii presence source
California (I. pacificus)
Alameda (Fedorova et al. 2014)
Butte (Rose et al. 2019)
Calaveras (Rose et al. 2019)
Contra Costa (Padgett and Bonilla 2011, Rose et al. 2019)
El Dorado (Rose et al. 2019)
Lake (Rose et al. 2019)
Los Angeles (Lane et al. 2013)
Marin (Rose et al. 2019)
Mariposa (Rose et al. 2019)
Mendocino (Eisen et al. 2004, 2010)
Nevada (Rose et al. 2019)
Sacramento (Rose et al. 2019)
San Luis Obispo (Rose et al. 2019)
San Mateo (Rose et al. 2019)
Santa Clara (Rose et al. 2019)
Santa Cruz (Rose et al. 2019)
Sonoma (Eisen et al. 2006, Rose et al. 2019)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
58 17 (29.3%) 0 (0%)
Connecticut (I. scapularis)
Fairfield (Crowder et al. 2010, Feldman et al. 2015), ArboNET, Personal communication
Hartford ArboNET
Litchfield (Diuk-Wasser et al. 2012, Feldman et al. 2015, Zolnik et al. 2015), ArboNET, Personal communication
Middlesex (Hoen et al. 2009, Diuk-Wasser et al. 2012), ArboNET
New Haven (Hanincová et al. 2006, Barbour et al. 2009, Feldman et al. 2015), ArboNET, Personal communication
New London (Diuk-Wasser et al. 2014), ArboNET
Tolland (States et al. 2014), ArboNET
Windham (Diuk-Wasser et al. 2014), ArboNET
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
8 8 (100%) 0 (0%)
District of Columbia (I. scapularis)
District of Columbia (Johnson et al. 2017)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
1 1 (100%) 0 (0%)
Georgia (I. scapularis)
Liberty (Lin et al. 2001)
McIntosh (Lin et al. 2001, Oliver et al. 2008)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
159 2 (1.26%) 0 (0%)
Illinois (I. scapularis)
Boone ArboNET
Carroll ArboNET
DuPage (Hamer et al. 2014), ArboNET
Fulton ArboNET
Jo Daviess ArboNET
Kendall ArboNET
Knox ArboNET
Lake (Jobe et al. 2007, Hamer et al. 2014), ArboNET
La Salle ArboNET
Lee ArboNET
Ogle (Diuk-Wasser et al. 2012, Hamer et al. 2014), ArboNET
Peoria ArboNET
Putnam (Diuk-Wasser et al. 2012, Schneider et al. 2015), ArboNET
Rock Island ArboNET
Shelby (Diuk-Wasser et al. 2012), ArboNET
Vermilion (Diuk-Wasser et al. 2012), ArboNET
Will ArboNET
Woodford ArboNET
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
102 18 (17.65%) 0 (0%)
Indiana (I. scapularis)
Carroll CDC Internal Database
Cass CDC Internal Database, ArboNET
Clark CDC Internal Database, ArboNET
Clay CDC Internal Database
Decatur CDC Internal Database, ArboNET
Elkhart CDC Internal Database, ArboNET
Fayette CDC Internal Database
Floyd CDC Internal Database
Franklin CDC Internal Database
Fulton CDC Internal Database
Gibson CDC Internal Database, ArboNET
Greene CDC Internal Database, ArboNET
Jasper CDC Internal Database
Jennings CDC Internal Database, ArboNET
Johnson CDC Internal Database
Kosciusko CDC Internal Database, ArboNET
LaGrange CDC Internal Database
Lake CDC Internal Database
La Porte CDC Internal Database
Marion CDC Internal Database
Marshall CDC Internal Database, ArboNET
Martin CDC Internal Database
Monroe CDC Internal Database, ArboNET
Montgomery CDC Internal Database
Morgan CDC Internal Database, ArboNET
Newton (Diuk-Wasser et al. 2012), CDC Internal Database, ArboNET
Noble CDC Internal Database
Owen CDC Internal Database, ArboNET
Parke CDC Internal Database
Porter (Hamer et al. 2014), CDC Internal Database, ArboNET
Posey CDC Internal Database, ArboNET
Pulaski (Crowder et al. 2010, Diuk-Wasser et al. 2012, Hamer et al. 2014, Steiner et al. 2014), CDC Internal Database, ArboNET
Putnam CDC Internal Database, ArboNET
Ripley CDC Internal Database, ArboNET
Scott CDC Internal Database
St. Joseph CDC Internal Database, ArboNET
Starke CDC Internal Database
Steuben CDC Internal Database, ArboNET
Tippecanoe CDC Internal Database
Warren CDC Internal Database
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
92 40 (43.48%) 0 (0%)
Iowa (I. scapularis)
Allamakee (Diuk-Wasser et al. 2012, Oliver et al. 2017), ArboNET
Clayton (Oliver et al. 2017)
Linn (Oliver et al. 2017)
Muscatine (Diuk-Wasser et al. 2012, Oliver et al. 2017), ArboNET
Winneshiek (Oliver et al. 2017)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
99 5 (5.05%) 0 (0%)
Louisiana (I. scapularis)
West Feliciana (Leydet and Liang 2014)
Number of parishes Number (%) of B. burgdorferi sensu stricto positive parishes Number (%) of B. mayonii positive parishes
64 1 (1.56%) 0 (0%)
Maine (I. scapularis)
Cumberland (Hoen et al. 2009, Diuk-Wasser et al. 2012, MacQueen et al. 2012), ArboNET
Hancock (Diuk-Wasser et al. 2012, Johnson et al. 2017), ArboNET
York (Steiner et al. 2014)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
16 3 (18.75%) 0 (0%)
Maryland (I. scapularis)
Caroline (Swanson and Norris 2007)
Cecil (Hoen et al. 2009, Diuk-Wasser et al. 2012), ArboNET
Frederick (Johnson et al. 2017)
Howard (Diuk-Wasser et al. 2012, Feldman et al. 2015), ArboNET, Supplemented with pers. comm.
Kent (Swanson and Norris 2007)
Queen Anne’s (Swanson and Norris 2007)
Somerset (Swanson and Norris 2007)
Wicomico (Swanson and Norris 2007)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
23 8 (34.78%) 0 (0%)
Massachusetts (I. scapularis)
Nantucket (Diuk-Wasser et al. 2014)
Worcester (Diuk-Wasser et al. 2012), ArboNET
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
14 2 (14.29%) 0 (0%)
Michigan (I. scapularis)
Alcona CDC Internal Database
Allegan (Hamer et al. 2014)
Benzie CDC Internal Database
Berrien CDC Internal Database
Calhoun CDC Internal Database
Charlevoix CDC Internal Database
Clinton CDC Internal Database
Dickinson CDC Internal Database
Houghton CDC Internal Database
Huron CDC Internal Database
Ionia (Hamer et al. 2010)
Iosco CDC Internal Database
Iron CDC Internal Database
Jackson CDC Internal Database
Kalamazoo CDC Internal Database
Leelanau CDC Internal Database
Manistee (Hamer et al. 2010), CDC Internal Database
Mason CDC Internal Database
Menominee (Diuk-Wasser et al. 2012, Hamer et al. 2014), CDC Internal Database, ArboNET
Muskegon (Hamer et al. 2014), CDC Internal Database
Oakland CDC Internal Database
Ontonagon CDC Internal Database
Van Buren (Diuk-Wasser et al. 2012, Hamer et al. 2012, 2014), CDC Internal Database, ArboNET
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
83 23 (21.71%) 0 (0%)
Minnesota (I. scapularis)
Aitkin CDC Internal Database, ArboNET
Anoka CDC Internal Database, ArboNET
Becker CDC Internal Database, ArboNET CDC Internal Database, ArboNET
Beltrami CDC Internal Database, ArboNET
Benton CDC Internal Database, ArboNET
Carlton (Hoen et al. 2009, Diuk-Wasser et al. 2012), CDC Internal Database, ArboNET
Cass (Hoen et al. 2009, Diuk-Wasser et al. 2012), CDC Internal Database, ArboNET CDC Internal Database, ArboNET
Chisago CDC Internal Database, ArboNET
Clearwater (Diuk-Wasser et al. 2012), CDC Internal Database, ArboNET CDC Internal Database, ArboNET
Crow Wing CDC Internal Database, ArboNET
Dakota CDC Internal Database, ArboNET
Goodhue CDC Internal Database, ArboNET
Hennepin CDC Internal Database, ArboNET
Houston CDC Internal Database
Hubbard (Hoen et al. 2009, Diuk-Wasser et al. 2012), CDC Internal Database, ArboNET CDC Internal Database, ArboNET
Kanabec CDC Internal Database, ArboNET
Kandiyohi (Diuk-Wasser et al. 2012), ArboNET
Koochiching CDC Internal Database, ArboNET
Mahnomen (Diuk-Wasser et al. 2012), ArboNET
Mille Lacs CDC Internal Database, ArboNET CDC Internal Database, ArboNET
Morrison CDC Internal Database, ArboNET CDC Internal Database, ArboNET
Olmsted CDC Internal Database, ArboNET
Otter Tail CDC Internal Database, ArboNET CDC Internal Database, ArboNET
Pine (Diuk-Wasser et al. 2012, Hamer et al. 2014), CDC Internal Database, ArboNET CDC Internal Database, ArboNET
Ramsey CDC Internal Database, ArboNET
Sherburne (Diuk-Wasser et al. 2012), ArboNET
St. Louis CDC Internal Database, ArboNET
Wadena CDC Internal Database, ArboNET
Washington (Hahn et al. 2016), CDC Internal Database, ArboNET
Winona CDC Internal Database, ArboNET CDC Internal Database, ArboNET
Wright CDC Internal Database, ArboNET
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
87 31 (35.63%) 9 (10.34%)
New Hampshire (I. scapularis)
Belknap NH DOH
Carroll NH DOH
Cheshire NH DOH
Grafton NH DOH
Hillsborough NH DOH
Merrimack NH DOH
Rockingham NH DOH
Strafford NH DOH
Sullivan NH DOH
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
10 9 (90%) 0 (0%)
New Jersey (I. scapularis)
Monmouth (Ullmann et al. 2005, Diuk-Wasser et al. 2012, Schulze et al. 2013), ArboNET
Salem (Diuk-Wasser et al. 2012), ArboNET
Sussex (Diuk-Wasser et al. 2012), ArboNET
Union (Adelson et al. 2004)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
21 4 (19.05%) 0 (0%)
New York (I. scapularis)
Albany NY DOH
Allegany NY DOH
Bronx (Hoen et al. 2009)
Broome NY DOH
Cattaraugus NY DOH
Cayuga NY DOH
Chautauqua NY DOH
Chemung NY DOH
Chenango NY DOH
Clinton NY DOH
Columbia NY DOH
Cortland NY DOH
Delaware NY DOH
Dutchess (Crowder et al. 2010), NY DOH
Erie NY DOH
Essex NY DOH
Franklin NY DOH
Fulton NY DOH
Genesee NY DOH
Greene (Prusinski et al. 2014), NY DOH
Hamilton NY DOH
Herkimer NY DOH
Jefferson NY DOH
Lewis NY DOH
Livingston NY DOH
Madison NY DOH
Monroe NY DOH
Montgomery NY DOH
Niagara NY DOH
Oneida (Diuk-Wasser et al. 2012), ArboNET, NY DOH
Onondaga NY DOH
Ontario NY DOH
Orange (Prusinski et al. 2014), NY DOH
Orleans NY DOH
Oswego NY DOH
Otsego NY DOH
Putnam (Aliota et al. 2014)
Rensselaer NY DOH
Richmond (VanAcker et al. 2019)
Rockland (Prusinski et al. 2014), NY DOH
Saratoga NY DOH
Schenectady NY DOH
Schoharie NY DOH
Schuyler NY DOH
Seneca NY DOH
St Lawrence NY DOH
Steuben NY DOH
Sullivan NY DOH
Suffolk (8,10,26), ArboNET, NY DOH
Tioga NY DOH
Tompkins NY DOH
Ulster (Prusinski et al. 2014), NY DOH
Warren NY DOH
Washington NY DOH
Wayne NY DOH
Westchester (Crowder et al. 2010, Diuk-Wasser et al. 2012, VanAcker et al. 2019), ArboNET, NY DOH
Wyoming NY DOH
Yates NY DOH
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
62 58 (93.50%) 0 (0%)
North Carolina (I. scapularis)
Alleghany CDC Internal Database
Ashe CDC Internal Database
Buncombe CDC Internal Database
Chatham (Smith et al. 2010, Maggi et al. 2019)
Currituck (Levine et al. 2017)
Dare (Levine et al. 2017)
Johnston CDC Internal Database
Madison CDC Internal Database
Rockingham CDC Internal Database
Stokes CDC Internal Database
Surry CDC Internal Database
Watauga CDC Internal Database, ArboNET
Wilkes CDC Internal Database
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
100 13 (13%) 0 (0%)
North Dakota (I. scapularis)
Grand Forks (Russart et al. 2014)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
53 1 (1.89%) 0 (0%)
Ohio (I. scapularis)
Coshocton (Wang et al. 2014)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
88 1 (1.14%) 0 (0%)
Pennsylvania (I. scapularis)
Adams (Hutchinson et al. 2015, Johnson et al. 2017),
Allegheny (Hutchinson et al. 2015, Simmons et al. 2020)
Armstrong (Hutchinson et al. 2015)
Beaver (Hutchinson et al. 2015)
Bedford (Hutchinson et al. 2015)
Berks (Diuk-Wasser et al. 2012, Hutchinson et al. 2015), ArboNET
Blair (Hutchinson et al. 2015)
Bradford (Hutchinson et al. 2015)
Bucks (Hutchinson et al. 2015)
Butler (Hutchinson et al. 2015)
Cambria (Hutchinson et al. 2015)
Cameron (Hutchinson et al. 2015)
Carbon (Hutchinson et al. 2015)
Centre (Hutchinson et al. 2015)
Chester (Hutchinson et al. 2015)
Clarion (Hutchinson et al. 2015)
Clearfield (Diuk-Wasser et al. 2012, Hutchinson et al. 2015), ArboNET
Clinton (Hutchinson et al. 2015)
Columbia (Hutchinson et al. 2015)
Crawford (Hutchinson et al. 2015)
Cumberland (Hutchinson et al. 2015)
Dauphin (Hutchinson et al. 2015)
Delaware (Hutchinson et al. 2015)
Elk (Hutchinson et al. 2015)
Erie (Diuk-Wasser et al. 2012, Steiner et al. 2014, Hutchinson et al. 2015), ArboNET
Fayette (Hutchinson et al. 2015)
Forest (Hutchinson et al. 2015)
Franklin (Hutchinson et al. 2015)
Fulton (Hutchinson et al. 2015)
Greene (Hutchinson et al. 2015)
Huntingdon (Hutchinson et al. 2015)
Indiana (Hutchinson et al. 2015)
Jefferson (Hutchinson et al. 2015)
Juniata (Hutchinson et al. 2015)
Lackawanna (Hutchinson et al. 2015)
Lancaster (Hutchinson et al. 2015)
Lawrence (Hutchinson et al. 2015)
Lebanon (Ford et al. 2015, Hutchinson et al. 2015)
Lehigh (Hutchinson et al. 2015)
Luzerne (Hutchinson et al. 2015)
Lycoming (Hutchinson et al. 2015)
McKean (Hutchinson et al. 2015)
Mercer (Hutchinson et al. 2015)
Mifflin (Hutchinson et al. 2015)
Monroe (Hutchinson et al. 2015)
Montgomery (Hutchinson et al. 2015)
Montour (Hutchinson et al. 2015)
Northampton (Hutchinson et al. 2015)
Northumberland (Hutchinson et al. 2015)
Perry (Hutchinson et al. 2015)
Philadelphia (Hutchinson et al. 2015)
Pike (Hutchinson et al. 2015)
Potter (Hutchinson et al. 2015)
Schuylkill (Hutchinson et al. 2015)
Snyder (Hutchinson et al. 2015)
Somerset (Hutchinson et al. 2015)
Sullivan (Hutchinson et al. 2015)
Susquehanna (Hutchinson et al. 2015)
Tioga (Hutchinson et al. 2015)
Union (Hutchinson et al. 2015)
Venango (Hutchinson et al. 2015)
Warren (Hutchinson et al. 2015)
Washington (Hutchinson et al. 2015)
Wayne (Hutchinson et al. 2015)
Westmoreland (Hutchinson et al. 2015)
Wyoming (Hutchinson et al. 2015)
York (Diuk-Wasser et al. 2012, Hutchinson et al. 2015), ArboNET
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
67 67 (100%) 0 (0%)
Rhode Island (I. scapularis)
Kent (Diuk-Wasser et al. 2012), ArboNET
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
5 1 (20%) 0 (0%)
South Carolina (I. scapularis)
Charleston (Oliver et al. 2000, 2008)
Georgetown (Oliver et al. 2008)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
46 2 (4.35%) 0 (0%)
South Dakota (I. scapularis)
Roberts (Maestas et al. 2018)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
66 1 (1.52%) 0 (0%)
Tennessee (I. scapularis)
Anderson (Hickling et al. 2018)
Claiborne (Hickling et al. 2018)
Davidson CDC Internal Database, ArboNET
Hamilton (Hickling et al. 2018)
Scott CDC Internal Database, ArboNET
Union (Hickling et al. 2018)
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
95 6 (6.32%) 0 (0%)
Vermont (I. scapularis)
Addison (Allen et al. 2019), CDC Internal Database
Bennington CDC Internal Database
Caledonia CDC Internal Database
Chittenden CDC Internal Database
Franklin CDC Internal Database
Lamoille CDC Internal Database
Orange CDC Internal Database
Orleans CDC Internal Database
Rutland CDC Internal Database
Washington CDC Internal Database
Windham CDC Internal Database
Windsor CDC Internal Database
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
14 12 (85.71%) 0 (0%)
Virginia (I. scapularis)
Albemarle (Johnson et al. 2017, Ferrell and Brinkerhoff 2018), CDC Internal Database
Bath CDC Internal Database
Buckingham (Ferrell and Brinkerhoff 2018)
Caroline (Ferrell and Brinkerhoff 2018), Supplemented with pers. comm.
Carroll CDC Internal Database
Chesapeake city CDC Internal Database
Chesterfield Pers. comm.
Covington city CDC Internal Database
Essex Pers. comm.
Fairfax (Diuk-Wasser et al. 2012), ArboNET
Fauquier (Ferrell and Brinkerhoff 2018)
Floyd CDC Internal Database, ArboNET
Galax city CDC Internal Database
Giles (Herrin et al. 2014)
Goochland (Ferrell and Brinkerhoff 2018), Supplemented with pers. comm.
Grayson CDC Internal Database, ArboNET
Greene (Johnson et al. 2017)CDC Internal Database
Hampton city CDC Internal Database
Highland CDC Internal Database
James City CDC Internal Database
King and Queen Pers. comm.
Martinsville city CDC Internal Database
Montgomery CDC Internal Database, ArboNET
Newport News city CDC Internal Database
Northampton CDC Internal Database
Patrick CDC Internal Database
Pittsylvania CDC Internal Database
Portsmouth city CDC Internal Database
Prince William (Johnson et al. 2017)
Pulaski (Herrin et al. 2014), CDC Internal Database, ArboNET
Smyth CDC Internal Database, ArboNET
Suffolk city CDC Internal Database
Tazewell CDC Internal Database
Virginia Beach city CDC Internal Database
Warren (Johnson et al. 2017), CDC Internal Database
Washington CDC Internal Database
Wythe CDC Internal Database, ArboNET
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
95 37 (38.95%) 0 (0%)
Washington (I. pacificus)
Clallam CDC Internal Database
Klickitat CDC Internal Database
Yakima CDC Internal Database
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
39 3 (7.69%) 0 (0%)
West Virginia (I. scapularis)
Hancock WV DOH
Jefferson WV DOH
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
55 2 (3.64%) 0 (0%)
Wisconsin (I. scapularis)
Ashland (Diuk-Wasser et al. 2012), CDC Internal Database, ArboNET
Barron (Turtinen et al. 2015), CDC Internal Database
Buffalo (Turtinen et al. 2015)
Chippewa (Diuk-Wasser et al. 2012, Turtinen et al. 2015), ArboNET
Clark (Turtinen et al. 2015)
Dunn (Diuk-Wasser et al. 2012), ArboNET
Eau Claire (Turtinen et al. 2015), CDC Internal Database, ArboNET
Forest CDC Internal Database
Iowa (Hamer et al. 2014), CDC Internal Database
Jackson (Diuk-Wasser et al. 2012, Lee et al. 2014), CDC Internal Database, ArboNET
Juneau CDC Internal Database
La Crosse (Turtinen et al. 2015)
Lincoln (Diuk-Wasser et al. 2012), ArboNET
Manitowoc (Turtinen et al. 2015)
Marathon (Diuk-Wasser et al. 2012, Turtinen et al. 2015), CDC Internal Database, ArboNET
Monroe (Hamer et al. 2014, Steiner et al. 2014) Hamer et al. 2014, Steiner et al. 2014
Oneida CDC Internal Database CDC Internal Database
Portage (Hoen et al. 2009, Diuk-Wasser et al. 2012), CDC Internal Database, ArboNET
Richland (Turtinen et al. 2015)
Sauk (Hoen et al. 2009, Diuk-Wasser et al. 2012), CDC Internal Database, ArboNET
Sawyer (Turtinen et al. 2015), CDC Internal Database
Sheboygan CDC Internal Database, ArboNET
St. Croix (Diuk-Wasser et al. 2012), ArboNET
Vernon (Hoen et al. 2009, Diuk-Wasser et al. 2012, Turtinen et al. 2015), ArboNET
Vilas (Diuk-Wasser et al. 2012, Turtinen et al. 2015, Westwood et al. 2020), ArboNET
Walworth (Caporale et al. 2005, Lee et al. 2014), CDC Internal Database
Washburn (Turtinen et al. 2015, Cross et al. 2018)
Waupaca CDC Internal Database
Number of counties Number (%) of B. burgdorferi sensu stricto positive counties Number (%) of B. mayonii positive counties
72 28 (38.89%) 1 (1.39%)
Open in a new tab

Fig. 1.

Fig. 1.

Open in a new tab

Reported distribution of Lyme disease spirochetes, B. burgdorferi s.s. and B. mayonii in host-seeking I. scapularis (eastern United States) or I. pacificus (western United States), relative to the previously reported distribution of these vector species. Ticks were considered present in a county if at least one tick was recorded (Eisen et al. [2016] or CDC [2020]). Counties where ticks have been reported without records of infection may be reported as such either if ticks were not tested or if the pathogen was not detected in tested samples.

B. burgdorferi s.s. was identified in I. pacificus in 20 counties spanning 2 western states (California and Washington; Table 1, Fig. 1). Most positive records were from northern and north-coastal California. B. mayonii was not found in I. pacificus.

Discussion

In the first U.S. map showing the distribution of counties where Lyme disease spirochetes (B. burgdorferi s.s. or B. mayonii) have been detected in host-seeking vector ticks, we show that infected ticks are reported most commonly from North Central, Northeast, and Mid-Atlantic states and from northern and north-coastal California, where Lyme disease cases are commonly reported in the eastern and western United States, respectively (Mead 2015, Adams et al. 2016, Schwartz et al. 2017). Consistent with previous reports, the distribution of Lyme disease spirochetes in host-seeking ticks (Diuk-Wasser et al. 2012) is more limited than the range of the vector ticks (Diuk-Wasser et al. 2010). Among the 35 eastern and 6 western states in which I. scapularis or I. pacificus is considered established (Eisen et al. 2016), Lyme disease spirochetes were reported from 26 (74%) and 2 (33%) states, respectively. At the county level, we report the presence of Lyme disease spirochetes in 404 counties, or roughly 26% of U.S. counties in which either tick is considered established (Eisen et al. 2016).

The reported distribution of B. burgdorferi s.s. and B. mayonii spirochetes in host-seeking ticks is almost certainly an underestimate of the actual distribution of these disease agents. Support for and participation in tick and tickborne pathogen surveillance has increased in the United States in recent years (Eisen and Paddock 2020), but tick collection and pathogen testing efforts have been limited, with most efforts focused on U.S. regions where Lyme disease cases are most commonly reported (Mader et al. 2020). In some instances, lack of records could represent lack of sampling effort or low prevalence of pathogens within sampled tick populations. Moreover, many counties in which Lyme disease spirochetes are maintained in enzootic cycles may have been excluded from our records either because the county of collection was not recorded in publications, or because the tests used to detect the pathogens were not adequately specific to exclude other B. burgdorferi s.l. spirochetes. Given our approach, we are confident in the distribution of presence records, but for counties where the pathogen has not been documented, we could not determine whether this represents true absence or simply a failure to detect the pathogen.

Consistent with previous studies, we show that B. burgdorferi s.s. in host-seeking I. scapularis is more common in counties north of the 39th parallel compared with more southern counties (Diuk-Wasser et al. 2006, 2012; Stromdahl and Hickling 2012). We acknowledge, however, that while recent funding for tick surveillance in low incidence Lyme disease states has increased, surveillance efforts have targeted low incidence states neighboring high incidence states in the Northeast, Mid-Atlantic, and North Central regions more than in the Southeast. In southern counties, I. scapularis nymphs seldomly ascend vegetation when host-seeking. As a result, nymphs infrequently bite humans and are rarely encountered by drag sampling or flagging in these regions (Diuk-Wasser et al. 2006, 2012; Arsnoe et al. 2015). Therefore, screening adults from southern counties for pathogens provides a more accurate assessment of spirochete presence than nymphal sampling and screening (Hickling et al. 2018). A parallel situation is observed in California, where the likelihood of encountering host-seeking is I. pacificus nymphs is greater in the north than the south, and detection of B. burgdorferi s.s. in host-seeking nymphs or adults is rare in southern California (Lane et al. 2013).

While presence of Lyme disease spirochetes in host-seeking vector ticks provides a better assessment of acarological risk for Lyme disease compared with tick presence alone, it is important to remember that within counties where Lyme disease spirochetes have been detected, risk of human encounters with infected ticks will vary based on the prevalence of infection in ticks and densities of host-seeking infected ticks (Eisen and Eisen 2016, Eisen and Paddock 2020). Here, a county could meet the criteria for presence if only a single infected tick was reported; our map does not differentiate a county with <1% prevalence from a county with >60% prevalence. While we provide foundational data on the reported distribution of Lyme disease spirochetes in the United States, additional acarological risk data coupled with human disease data will provide a more comprehensive assessment of Lyme disease risk.

The data presented here provide the first county-level map of the distribution of Lyme disease spirochetes in host-seeking ticks in the United States. Through continued surveillance and reporting, additional counties are likely to be added, and it may be possible to report densities of infected host-seeking ticks for many jurisdictions. Such data may prove useful for targeting prevention resources to communities at risk for exposure to infected ticks.

Acknowledgments

We thank Craig Mincic, Isabel Sheets, and Terry Hoiness for their assistance with ArboNET data and queries and public health partners who submitted surveillance data to ArboNET or ticks to CDC for testing.

References Cited

  1. Adams, D. A., Thomas K. R., Jajosky R. A., Foster L., Sharp P., Onweh D. H., Schley A. W., and Anderson W. J.; Nationally Notifiable Infectious Conditions Group . 2016. Summary of notifiable infectious diseases and conditions - United States, 2014. MMWR. Morb. Mortal. Wkly. Rep. 63: 1–152. [DOI] [PubMed] [Google Scholar]
  2. Adelson, M. E., Rao R. V., Tilton R. C., Cabets K., Eskow E., Fein L., Occi J. L., and Mordechai E.. . 2004. Prevalence of Borrelia burgdorferi, Bartonella spp., Babesia microti, and Anaplasma phagocytophila in Ixodes scapularis ticks collected in Northern New Jersey. J. Clin. Microbiol. 42: 2799–2801. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Aliota, M. T., A. P.Dupuis, 2nd, Wilczek M. P., Peters R. J., Ostfeld R. S., and Kramer L. D.. . 2014. The prevalence of zoonotic tick-borne pathogens in Ixodes scapularis collected in the Hudson Valley, New York State. Vector Borne Zoonotic Dis. 14: 245–250. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Allen, D., Borgmann-Winter B., Bashor L., and Ward J.. . 2019. The density of the Lyme disease vector Ixodes scapularis (blacklegged tick) differs between the Champlain Valley and Green Mountains, Vermont. Northeast. Nat. 26: 545. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Altschul, S. F., Gish W., Miller W., Myers E. W., and Lipman D. J.. . 1990. Basic local alignment search tool. J. Mol. Biol. 215: 403–410. [DOI] [PubMed] [Google Scholar]
  6. Arsnoe, I. M., Hickling G. J., Ginsberg H. S., McElreath R., and Tsao J. I.. . 2015. Different populations of blacklegged tick nymphs exhibit differences in questing behavior that have implications for human Lyme disease risk. PLoS One 10: e0127450. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Barbour, A. G., Bunikis J., Travinsky B., Hoen A. G., Diuk-Wasser M. A., Fish D., and Tsao J. I.. . 2009. Niche partitioning of Borrelia burgdorferi and Borrelia miyamotoi in the same tick vector and mammalian reservoir species. Am. J. Trop. Med. Hyg. 81: 1120–1131. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Caporale, D. A., Johnson C. M., and Millard B. J.. . 2005. Presence of Borrelia burgdorferi (Spirochaetales: Spirochaetaceae) in southern Kettle Moraine State Forest, Wisconsin, and characterization of strain W97F51. J. Med. Entomol. 42: 457–472. [DOI] [PubMed] [Google Scholar]
  9. CDC . 1999. Recommendations for the use of Lyme disease vaccine recommendations of the Advisory Committee on Immunization Practices (ACIP).https://www.cdc.gov/mmwr/preview/mmwrhtml/rr4807a1.htm. Accessed 9 November 2020.
  10. CDC . 2020. Tick surveillance.https://www.cdc.gov/ticks/surveillance/index.html. Accessed 9 November 2020.
  11. Cross, S. T., Kapuscinski M. L., Perino J., Maertens B. L., Weger-Lucarelli J., Ebel G. D., and Stenglein M. D.. . 2018. Co-infection patterns in individual Ixodes scapularis ticks reveal associations between viral, eukaryotic and bacterial microorganisms. Viruses 10: 388. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Crowder, C. D., Matthews H. E., Schutzer S., Rounds M. A., Luft B. J., Nolte O., Campbell S. R., Phillipson C. A., Li F., Sampath R., . et al. 2010. Genotypic variation and mixtures of Lyme Borrelia in Ixodes ticks from North America and Europe. PLoS One 5: e10650. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Dennis, D. T., Nekomoto T. S., Victor J. C., Paul W. S., and Piesman J.. . 1998. Reported distribution of Ixodes scapularis and Ixodes pacificus (Acari: Ixodidae) in the United States. J. Med. Entomol. 35: 629–638. [DOI] [PubMed] [Google Scholar]
  14. Diuk-Wasser, M. A., Gatewood A. G., Cortinas M. R., Yaremych-Hamer S., Tsao J., Kitron U., Hickling G., Brownstein J. S., Walkder E., Piesman J., and Fish D.. . 2006. Spatiotemportal patterns of host-seeking Ixodes scapularis nymphs (Acari: Ixodidae) in the United States. J. Med. Entomol. 43: 166–176. [DOI] [PubMed] [Google Scholar]
  15. Diuk-Wasser, M. A., Hoen A. G., Cislo P., Brinkerhoff R., Hamer S. A., Rowland M., Cortinas R., Vourc’h G., Melton F., Hickling G. J., . et al. 2012. Human risk of infection with Borrelia burgdorferi, the Lyme disease agent, in eastern United States. Am. J. Trop. Med. Hyg. 86: 320–327. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Diuk-Wasser, M. A., Vourc’h G., Cislo P., Hoen A. G., Melton F., Hamer S. A., Rowland M., Cortinas R., Hickling G. J., Tsao J. I., . et al. 2010. Field and climate-based model for predicting the density of host-seeking nymphal Ixodes scapularis, an important vector of tick-borne disease agents in the eastern United States. Global Ecol. Biogeograh. 19: 504–514. [Google Scholar]
  17. Diuk-Wasser, M. A., Liu Y., Steeves T. K., Folsom-O’Keefe C., Dardick K. R., Lepore T., Bent S. J., Usmani-Brown S., Telford S. R., Fish D., . et al. 2014. Monitoring human babesiosis emergence through vector surveillance, New England, USA. Emerg. Infect. Dis. 20: 225–231. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Eisen, L., and Eisen R. J.. . 2016. Critical evaluation of the linkage between tick-based risk measures and the occurrence of Lyme disease cases. J. Med. Entomol. 53: 1050–1062. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Eisen, R. J., and Eisen L.. . 2018. The blacklegged tick, Ixodes scapularis: an increasing public health concern. Trends Parasitol. 34: 295–309. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Eisen, R. J., and Paddock C. D.. . 2020. Tick and tickborne pathogen surveillance as a public health tool in the United States. J. Med. Entomol. doi: 10.1093/jme/tjaa087. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Eisen, R. J., Mun J., Eisen L., and Lane R. S.. . 2004. Life stage-related differences in density of questing ticks and infection with Borrelia burgdorferi sensu lato within a single cohort of Ixodes pacificus (Acari: Ixodidae). J. Med. Entomol. 41: 768–773. [DOI] [PubMed] [Google Scholar]
  22. Eisen, R. J., Eisen L., and Lane R. S.. . 2006. Predicting density of Ixodes pacificus nymphs in dense woodlands in Mendocino County, California, based on geographic information systems and remote sensing versus field-derived data. Am. J. Trop. Med. Hyg. 74: 632–640. [PubMed] [Google Scholar]
  23. Eisen, R. J., Eisen L., Girard Y. A., Fedorova N., Mun J., Slikas B., Leonhard S., Kitron U., and Lane R. S.. . 2010. A spatially-explicit model of acarological risk of exposure to Borrelia burgdorferi-infected Ixodes pacificus nymphs in northwestern California based on woodland type, temperature, and water vapor. Ticks Tick. Borne. Dis. 1: 35–43. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Eisen, R. J., Eisen L., and Beard C. B.. . 2016. County-scale distribution of Ixodes scapularis and Ixodes pacificus (Acari: Ixodidae) in the continental United States. J. Med. Entomol. 53: 349–386. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Eisen, R. J., Kugeler K. J., Eisen L., Beard C. B., and Paddock C. D.. . 2017. Tick-borne zoonoses in the United States: persistent and emerging threats to human health. Ilar J. 58: 319–335. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Falco, R. C., and Fish D.. . 1988. A survey of tick bites acquired in a Lyme disease endemic area in southern New York state. Ann. N. Y. Acad. Sci. 539: 456–457. [Google Scholar]
  27. Fedorova, N., Kleinjan J. E., James D., Hui L. T., Peeters H., and Lane R. S.. . 2014. Remarkable diversity of tick or mammalian-associated Borreliae in the metropolitan San Francisco Bay Area, California. Ticks Tick. Borne. Dis. 5: 951–961. [DOI] [PubMed] [Google Scholar]
  28. Feldman, K. A., Connally N. P., Hojgaard A., Jones E. H., White J. L., and Hinckley A. F.. . 2015. Abundance and infection rates of Ixodes scapularis nymphs collected from residential properties in Lyme disease-endemic areas of Connecticut, Maryland, and New York. J. Vector Ecol. 40: 198–201. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Ferrell, A. M., and Brinkerhoff R. J.. . 2018. Using landscape analysis to test hypotheses about drivers of tick abundance and infection prevalence with Borrelia burgdorferi. Int. J. Environ. Res. Public Health 15: 737. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Ford, K., Nadolny R., Stromdahl E., and Hickling G.. . 2015. Tick surveillance and disease prevention on the Appalachian trail. Park Sci. 32: 36. [Google Scholar]
  31. Graham, C. B., Maes S. E., Hojgaard A., Fleshman A. C., Sheldon S. W., and Eisen R. J.. . 2018. A molecular algorithm to detect and differentiate human pathogens infecting Ixodes scapularis and Ixodes pacificus (Acari: Ixodidae). Ticks Tick. Borne. Dis. 9: 390–403. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Hahn, M. B., Jarnevich C. S., Monaghan A. J., and Eisen R. J.. . 2016. Modeling the geographic distribution of Ixodes scapularis and Ixodes pacificus (Acari: Ixodidae) in the contiguous United States. J. Med. Entomol. 53: 1176–1191. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Hamer, S. A., Tsao J. I., Walker E. D., and Hickling G. J.. . 2010. Invasion of the lyme disease vector Ixodes scapularis: implications for Borrelia burgdorferi endemicity. Ecohealth 7: 47–63. [DOI] [PubMed] [Google Scholar]
  34. Hamer, S. A., Hickling G. J., Sidge J. L., Walker E. D., and Tsao J. I.. . 2012. Synchronous phenology of juvenile Ixodes scapularis, vertebrate host relationships, and associated patterns of Borrelia burgdorferi ribotypes in the midwestern United States. Ticks Tick. Borne. Dis. 3: 65–74. [DOI] [PubMed] [Google Scholar]
  35. Hamer, S. A., Hickling G. J., Walker E. D., and Tsao J. I.. . 2014. Increased diversity of zoonotic pathogens and Borrelia burgdorferi strains in established versus incipient Ixodes scapularis populations across the Midwestern United States. Infect. Genet. Evol. 27: 531–542. [DOI] [PubMed] [Google Scholar]
  36. Hanincová, K., Kurtenbach K., Diuk-Wasser M., Brei B., and Fish D.. . 2006. Epidemic spread of Lyme borreliosis, northeastern United States. Emerg. Infect. Dis. 12: 604–611. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Herrin, B. H., Zajac A. M., and Little S. E.. . 2014. Confirmation of Borrelia burgdorferi sensu stricto and Anaplasma phagocytophilum in Ixodes scapularis, Southwestern Virginia. Vector Borne Zoonotic Dis. 14: 821–823. [DOI] [PubMed] [Google Scholar]
  38. Hickling, G. J., Kelly J. R., Auckland L. D., and Hamer S. A.. . 2018. Increasing prevalence of Borrelia burgdorferi sensu stricto–infected blacklegged ticks in Tennessee valley, Tennessee, USA. Emerg. Infect. Dis. 24: 1713–1716. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Hoen, A. G., Margos G., Bent S. J., Diuk-Wasser M. A., Barbour A., Kurtenbach K., and Fish D.. . 2009. Phylogeography of Borrelia burgdorferi in the eastern United States reflects multiple independent Lyme disease emergence events. Proc. Natl. Acad. Sci. USA 106: 15013–15018. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. Hutchinson, M. L., Strohecker M. D., Simmons T. W., Kyle A. D., and Helwig M. W.. . 2015. Prevalence rates of Borrelia burgdorferi (Spirochaetales: Spirochaetaceae), Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae), and Babesia microti (Piroplasmida: Babesiidae) in host-seeking Ixodes scapularis (Acari: Ixodidae) from Pennsylvania. J. Med. Entomol. 52: 693–698. [DOI] [PubMed] [Google Scholar]
  41. Jobe, D. A., Nelson J. A., Adam M. D., and Martin S. A.. . 2007. Lyme disease in urban areas, Chicago. Emerg Infect Dis. 13: 1799–1800. [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Johnson, T. L., Graham C. B., Boegler K. A., Cherry C. C., Maes S. E., Pilgard M. A., Hojgaard A., Buttke D. E., and Eisen R. J.. . 2017. Prevalence and diversity of tick-borne pathogens in Nymphal Ixodes scapularis (Acari: Ixodidae) in Eastern National Parks. J. Med. Entomol. 54: 742–751. [DOI] [PMC free article] [PubMed] [Google Scholar]
  43. Kugeler, K. J., Farley G. M., Forrester J. D., and Mead P. S.. . 2015. Geographic distribution and expansion of human Lyme disease, United States. Emerg. Infect. Dis. 21: 1455–1457. [DOI] [PMC free article] [PubMed] [Google Scholar]
  44. Lane, R. S., Fedorova N., Kleinjan J. E., and Maxwell M.. . 2013. Eco-epidemiological factors contributing to the low risk of human exposure to ixodid tick-borne Borreliae in southern California, USA. Ticks Tick. Borne. Dis. 4: 377–385. [DOI] [PubMed] [Google Scholar]
  45. Lee, X., Coyle D. R., Johnson D. K., Murphy M. W., McGeehin M. A., Murphy R. J., Raffa K. F., and Paskewitz S. M.. . 2014. Prevalence of Borrelia burgdorferi and Anaplasma phagocytophilum in Ixodes scapularis (Acari: Ixodidae) nymphs collected in managed red pine forests in Wisconsin. J. Med. Entomol. 51: 694–701. [DOI] [PubMed] [Google Scholar]
  46. Lehane, A., Parise C., Evans C., Beati L., Nicholson W. L., and Eisen R. J.. . 2020. Reported county-level distribution of the American dog tick (Acari: ixodidae) in the contiguous United States. J. Med. Entomol. 57: 131–155. [DOI] [PMC free article] [PubMed] [Google Scholar]
  47. Levine, J. F., Apperson C. S., Levin M., Kelly T. R., Kakumanu M. L., Ponnusamy L., Sutton H., Salger S. A., Caldwell J. M., and Szempruch A. J.. . 2017. Stable Transmission of Borrelia burgdorferi sensu stricto on the outer banks of North Carolina. Zoonoses Public Health. 64: 337–354. [DOI] [PMC free article] [PubMed] [Google Scholar]
  48. Leydet, B. F., and Liang F. -T.. . 2014. Detection of Lyme Borrelia in questing Ixodes scapularis (Acari: Ixodidae) and small mammals in Louisiana: table 1. J. Med. Entomol. 51: 278–282. [DOI] [PMC free article] [PubMed] [Google Scholar]
  49. Lin, T., J. H.Oliver, Jr, Gao L., T. M.Kollars, Jr, and Clark K. L.. . 2001. Genetic heterogeneity of Borrelia burgdorferi sensu lato in the southern United States based on restriction fragment length polymorphism and sequence analysis. J. Clin. Microbiol. 39: 2500–2507. [DOI] [PMC free article] [PubMed] [Google Scholar]
  50. MacQueen, D. D., Lubelczyk C., Elias S. P., Cahill B. K., Mathers A. J., Lacombe E. H., Rand P. W., and R. P.Smith, Jr. 2012. Genotypic diversity of an emergent population of Borrelia burgdorferi at a coastal Maine island recently colonized by Ixodes scapularis. Vector Borne Zoonotic Dis. 12: 456–461. [DOI] [PubMed] [Google Scholar]
  51. Mader, E. M., Ganser C., Geiger A., Harrington L. C., Foley J., Smith R. L., Mateus-Pinilla N., Teel P. D., and Eisen R. J.. . 2020. A survey of tick surveillance and control practices in the United States. J. Med. Entomol. doi: 10.1093/jme/tjaa094. [DOI] [PMC free article] [PubMed] [Google Scholar]
  52. Maestas, L. P., Mays S. E., Britten H. B., Auckland L. D., and Hamer S. A.. . 2018. Surveillance for Ixodes scapularis (Acari Ixodidae) and Borrelia burgdorferi in Eastern South Dakota State Parks and nature areas. J. Med. Entomol. 55: 1549–1554. [DOI] [PubMed] [Google Scholar]
  53. Maggi, R. G., Toliver M., Richardson T., Mather T., and Breitschwerdt E. B.. . 2019. Regional prevalences of Borrelia burgdorferi, Borrelia bissettiae, and Bartonella henselae in Ixodes affinis, Ixodes pacificus and Ixodes scapularis in the USA. Ticks Tick. Borne. Dis. 10: 360–364. [DOI] [PubMed] [Google Scholar]
  54. Marconi, R. T., Liveris D., and Schwartz I.. . 1995. Identification of novel insertion elements, restriction fragment length polymorphism patterns, and discontinuous 23S rRNA in Lyme disease spirochetes: phylogenetic analyses of rRNA genes and their intergenic spacers in Borrelia japonica sp. nov. and genomic group 21038 (Borrelia andersonii sp. nov.) isolates. J. Clin. Microbiol. 33: 2427–2434. [DOI] [PMC free article] [PubMed] [Google Scholar]
  55. Margos, G., Hojgaard A., Lane R. S., Cornet M., Fingerle V., Rudenko N., Ogden N., Aanensen D. M., Fish D., and Piesman J.. . 2010. Multilocus sequence analysis of Borrelia bissettii strains from North America reveals a new Borrelia species, Borrelia kurtenbachii. Ticks Tick. Borne. Dis. 1: 151–158. [DOI] [PMC free article] [PubMed] [Google Scholar]
  56. Margos, G., Lane R. S., Fedorova N., Koloczek J., Piesman J., Hojgaard A., Sing A., and Fingerle V.. . 2016. Borrelia bissettiae sp. nov. and Borrelia californiensis sp. nov. prevail in diverse enzootic transmission cycles. Int. J. Syst. Evol. Microbiol. 66: 1447–1452. [DOI] [PMC free article] [PubMed] [Google Scholar]
  57. Mather, T. N., Nicholson M. C., Donnelly E. F., and Matyas B. T.. . 1996. Entomologic index for human risk of Lyme disease. Am. J. Epidemiol. 144: 1066–1069. [DOI] [PubMed] [Google Scholar]
  58. Mead, P. S. 2015. Epidemiology of Lyme disease. Infect. Dis. Clin. North Am. 29: 187–210. [DOI] [PubMed] [Google Scholar]
  59. Oliver, J. H., Clark K. L., Chandler F. W., Tao L., James A. M., Banks C. W., Huey L. O., Banks A. R., Williams D. C., and Durden L. A.. . 2000. Isolation, cultivation, and characterization of Borrelia burgdorferi from rodents and ticks in the Charleston area of South Carolina. J. Clin. Microbiol. 38: 120–124. [DOI] [PMC free article] [PubMed] [Google Scholar]
  60. Oliver, J. H., Gao L., and Lin T.. . 2008. Comparison of the spirochete Borrelia burgdorferi S. L. isolated from the tick Ixodes scapularis in southeastern and northeastern United States. J. Parasitol. 94: 1351–1356. [DOI] [PubMed] [Google Scholar]
  61. Oliver, J. D., Bennett S. W., Beati L., and Bartholomay L. C.. . 2017. Range expansion and increasing Borrelia burgdorferi infection of the tick Ixodes scapularis (Acari: Ixodidae) in Iowa, 1990–2013. J. Med. Entomol. 54: 1727–1734. [DOI] [PubMed] [Google Scholar]
  62. Padgett, K. A., and Bonilla D. L.. . 2011. Novel exposure sites for nymphal Ixodes pacificus within picnic areas. Ticks Tick. Borne. Dis. 2: 191–195. [DOI] [PubMed] [Google Scholar]
  63. Postic, D., Ras N. M., Lane R. S., Hendson M., and Baranton G.. . 1998. Expanded diversity among Californian Borrelia isolates and description of Borrelia bissettii sp. nov. (formerly Borrelia group DN127). J. Clin. Microbiol. 36: 3497–3504. [DOI] [PMC free article] [PubMed] [Google Scholar]
  64. Postic, D., Garnier M., and Baranton G.. . 2007. Multilocus sequence analysis of atypical Borrelia burgdorferi sensu lato isolates - Description of Borrelia californiensis sp. nov., and genomospecies 1 and 2. Int. J. Med. Microbiol. 297: 263–271. [DOI] [PubMed] [Google Scholar]
  65. Pritt, B. S., Respicio-Kingry L. B., Sloan L. M., Schriefer M. E., Replogle A. J., Bjork J., Liu G., Kingry L. C., Mead P. S., Neitzel D. F., . et al. 2016. Borrelia mayonii sp. nov., a member of the Borrelia burgdorferi sensu lato complex, detected in patients and ticks in the upper midwestern United States. Int. J. Syst. Evol. Microbiol. 66: 4878–4880. [DOI] [PMC free article] [PubMed] [Google Scholar]
  66. Prusinski, M. A., Kokas J. E., Hukey K. T., Kogut S. J., Lee J., and Backenson P. B.. . 2014. Prevalence of Borrelia burgdorferi (Spirochaetales: Spirochaetaceae), Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae), and Babesia microti (Piroplasmida: Babesiidae) in Ixodes scapularis (Acari: Ixodidae) collected from recreational lands in the Hudson Valley Region, New York State. J. Med. Entomol. 51: 226–236. [DOI] [PubMed] [Google Scholar]
  67. Rose, I., Yoshimizu M. H., Bonilla D. L., Fedorova N., Lane R. S., and Padgett K. A.. . 2019. Phylogeography of Borrelia spirochetes in Ixodes pacificus and Ixodes spinipalpis ticks highlights differential acarological risk of tick-borne disease transmission in northern versus southern California. PLoS One 14: e0214726. [DOI] [PMC free article] [PubMed] [Google Scholar]
  68. Rosenberg, R., Lindsey N. P., Fischer M., Gregory C. J., Hinckley A. F., Mead P. S., Paz-Bailey G., Waterman S. H., Drexler N. A., Kersh G. J., . et al. 2018. Vital signs: trends in reported vectorborne disease cases — United States and territories, 2004–2016. Morb. Mortal. Wkly. Rep. 67: 496–501. [DOI] [PMC free article] [PubMed] [Google Scholar]
  69. Rudenko, N., Golovchenko M., Lin T., Gao L., Grubhoffer L., and J. H.Oliver, Jr. 2009. Delineation of a new species of the Borrelia burgdorferi Sensu Lato Complex, Borrelia americana sp. nov. J. Clin. Microbiol. 47: 3875–3880. [DOI] [PMC free article] [PubMed] [Google Scholar]
  70. Rudenko, N., Golovchenko M., Grubhoffer L., and Oliver J. H.. . 2011a. Updates on Borrelia burgdorferi sensu lato complex with respect to public health. Ticks Tick. Borne. Dis. 2: 123–128. [DOI] [PMC free article] [PubMed] [Google Scholar]
  71. Rudenko, N., Golovchenko M., Grubhoffer L., and Oliver J. H.. . 2011b. Borrelia carolinensis sp. nov., a novel species of the Borrelia burgdorferi sensu lato complex isolated from rodents and a tick from the south-eastern USA. Int. J. Syst. Evol. Microbiol. 61: 381–383. [DOI] [PMC free article] [PubMed] [Google Scholar]
  72. Russart, N. M., Dougherty M. W., and Vaughan J. A.. . 2014. Survey of ticks (Acari: Ixodidae) and tick-borne pathogens in North Dakota. J. Med. Entomol. 51: 1087–1090. [DOI] [PubMed] [Google Scholar]
  73. Schneider, S. C., Parker C. M., Miller J. R., Page Fredericks L., and Allan B. F.. . 2015. Assessing the contribution of songbirds to the movement of ticks and Borrelia burgdorferi in the Midwestern United States during fall migration. Ecohealth. 12: 164–173. [DOI] [PubMed] [Google Scholar]
  74. Schulze, T. L., Jordan R. A., Healy S. P., and Roegner V. E.. . 2013. Detection of Babesia microti and Borrelia burgdorferi in host-seeking Ixodes scapularis (Acari: Ixodidae) in Monmouth County, New Jersey. J. Med. Entomol. 50: 379–383. [DOI] [PubMed] [Google Scholar]
  75. Schwartz, A. M., Hinckley A. F., Mead P. S., Hook S. A., and Kugeler K. J.. . 2017. Surveillance for Lyme disease — United States, 2008–2015. MMWR Surveill. Summ. 66: 1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  76. Simmons, A. E., Manges A. B., Bharathan T., Tepe S. L., McBride S. E., DiLeonardo M. Q., Duchamp J. E., and Simmons T. W.. . 2020. Lyme disease risk of exposure to blacklegged ticks (Acari: Ixodidae) infected with Borrelia burgdorferi (Spirochaetales: Spirochaetaceae) in Pittsburgh Regional Parks. J. Med. Entomol. 57: 273–280. [DOI] [PubMed] [Google Scholar]
  77. Smith, M. P., Ponnusamy L., Jiang J., Ayyash L. A., Richards A. L., and Apperson C. S.. . 2010. Bacterial pathogens in ixodid ticks from a Piedmont County in North Carolina: prevalence of rickettsial organisms. Vector Borne Zoonotic Dis. 10: 939–952. [DOI] [PubMed] [Google Scholar]
  78. Springer, Y. P., Eisen L., Beati L., James A. M., and Eisen R. J.. . 2014. Spatial distribution of counties in the continental United States with records of occurrence of Amblyomma americanum (Ixodida: Ixodidae). J. Med. Entomol. 51: 342–351. [DOI] [PMC free article] [PubMed] [Google Scholar]
  79. States, S. L., Brinkerhoff R. J., Carpi G., Steeves T. K., Folsom-O’Keefe C., DeVeaux M., and Diuk-Wasser M. A.. . 2014. Lyme disease risk not amplified in a species-poor vertebrate community: similar Borrelia burgdorferi tick infection prevalence and OspC genotype frequencies. Infect. Genet. Evol. 27: 566–575. [DOI] [PMC free article] [PubMed] [Google Scholar]
  80. Steiner, F. E., Pinger R. R., Vann C. N., Grindle N., Civitello D., Clay K., and Fuqua C.. . 2014. Infection and co-infection rates of Anaplasma phagocytophilum variants, Babesia spp., Borrelia burgdorferi, and the rickettsial endosymbiont in Ixodes scapularis (Acari: Ixodidae) from sites in Indiana, Maine, Pennsylvania, and Wisconsin. J. Med. Entomol. 45: 289–297. [DOI] [PubMed] [Google Scholar]
  81. Stromdahl, E. Y., and Hickling G. J.. . 2012. Beyond Lyme: aetiology of tick-borne human diseases with emphasis on the south-eastern United States. Zoonoses Public Health 59: 48–64. [DOI] [PubMed] [Google Scholar]
  82. Swanson, K. I., and Norris D. E.. . 2007. Co-circulating microorganisms in questing Ixodes scapularis nymphs in Maryland. J. Vector Ecol. 32: 243–251. [DOI] [PMC free article] [PubMed] [Google Scholar]
  83. Tijsse-Klasen, E., Koopmans M. P. G., and Sprong H.. . 2014. Tick-borne pathogen – reversed and conventional discovery of disease. Front. Public Heal. 2: 73. [DOI] [PMC free article] [PubMed] [Google Scholar]
  84. Turtinen, L. W., Kruger A. N., and Hacker M. M.. . 2015. Prevalence of Borrelia burgdorferi in adult female ticks (Ixodes scapularis), Wisconsin 2010–2013. J. Vector Ecol. 40: 195–197. [DOI] [PubMed] [Google Scholar]
  85. Ullmann, A. J., Gabitzsch E. S., Schulze T. L., Zeidner N. S., and Piesman J.. . 2005. Three multiplex assays for detection of Borrelia burgdorferi sensu lato and Borrelia miyamotoi sensu lato in field-collected Ixodes nymphs in North America. J. Med. Entomol. 42: 1057–1062. [DOI] [PubMed] [Google Scholar]
  86. VanAcker, M. C., Little E. A. H., Molaei G., Bajwa W. I., and Diuk-Wasser M. A.. . 2019. Enhancement of risk for lyme disease by landscape connectivity, New York, New York, USA. Emerg. Infect. Dis. 25: 1136–1143. [DOI] [PMC free article] [PubMed] [Google Scholar]
  87. Wang, P., Glowacki M. N., Hoet A. E., Needham G. R., Smith K. A., Gary R. E., and Li X.. . 2014. Emergence of Ixodes scapularis and Borrelia burgdorferi, the Lyme disease vector and agent, in Ohio. Front. Cell. Infect. Microbiol. 4: 70. [DOI] [PMC free article] [PubMed] [Google Scholar]
  88. Westwood, M. L., Peters J. L., and Rooney T. P.. . 2020. Prevalence and coinfection of three tick-borne pathogens in questing adult blacklegged ticks Ixodes scapularis (Vilas county, Wisconsin). Vector-Borne Zoonotic Dis. 20: 633–635. doi: vbz.2020.2619. [DOI] [PubMed] [Google Scholar]
  89. Zolnik, C. P., Falco R. C., Kolokotronis S. O., and Daniels T. J.. . 2015. No observed effect of landscape fragmentation on pathogen infection prevalence in blacklegged ticks (Ixodes scapularis) in the Northeastern United States. PLoS One 10: e0139473. [DOI] [PMC free article] [PubMed] [Google Scholar]

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