Table 1.
Native or recently established ixodid tick species documented to bite humans in the United States (US).
| Tick speciesa | Total tick specimens recorded to infest humansf | Number (%) of ticks recorded to infest humans by life stage for a given speciesg | Geographical distribution in the US | Primary host preference | Selected associated human pathogens or medical conditions | |||
|---|---|---|---|---|---|---|---|---|
| Number | % | Adult | Nymph | Larva | ||||
| Ixodes scapularis b | 158,008 | 67.3 | 60,426 (55) | 46,481 (42) | 2,796 (3) | Eastern | Wide range of mammals, Birds, Lizards |
Anaplasma phagocytophilum
Babesia microti Borrelia burgdorferi s.s.h Borrelia mayonii Borrelia miyamotoi Powassan virus |
| Amblyomma americanum | 36,004 | 15.4 | 5,605 (43) | 6,396 (49) | 1,137 (9) | Eastern | Ungulates, Carnivores, Birds | Bourbon virus Ehrlichia chaffeensis Ehrlichia ewingii Heartland virus Red meat allergy |
| Dermacentor variabilis c | 26,624 | 11.3 | 19,391 (99.6) | 73 (0.4) | 11 (<0.1) | Eastern, Far Westernc | Rodents, Carnivores |
Francisella
tularensis Rickettsia rickettsii Tick paralysis |
| Ixodes pacificus b | 4,158 | 1.8 | 2,187 (84) | 384 (15) | 26 (1) | Far Western | Wide range of mammals, Birds, Lizards |
Anaplasma
phagocytophilum Borrelia burgdorferi s.s. Borrelia miyamotoi |
| Dermacentor andersoni b | 3,518 | 1.5 | 2,970 (99.6) | 10 (0.3) | 3 (0.1) | Western | Wide range of mammals | Colorado tick fever virus Francisella
tularensis
Rickettsia rickettsii Tick paralysis |
| Ixodes cookei b | 2,494 | 1.1 | 130 (19) | 513 (75) | 38 (6) | Eastern | Rodents, Carnivores | Powassan virus |
| Dermacentor occidentalis | 809 | 0.3 | 562 (81) | 126 (18) | 10 (1) | Far Western | Wide range of mammals | Rickettsia philipii |
| Rhipicephalus sanguineus s.l.d | 714 | 0.3 | 175 (53) | 138 (42) | 18 (5) | Widely in the US | Dogs | Rickettsia rickettsii |
| Dermacentor albipictus b | 465 | 0.2 | 31 (66) | 4 (8) | 12 (26) | Widely in the US | Ungulates | Babesia duncani |
| Amblyomma maculatum | 335 | 0.1 | 237 (94) | 14 (6) | 0 (0) | Southeastern | Wide range of mammals, Birds | Rickettsia parkeri |
| Ixodes marxi | 232 | 0.1 | 19 (41) | 25 (54) | 2 (4) | Eastern | Rodents, Carnivores | None |
| Ixodes uriae | 224 | 0.1 | 2 (29) | 5 (71) | 0 (0) | Maine, Oregon, Alaska | Seabirds | Borrelia garinii |
| Amblyomma cajennense s.l.d | 222 | <0.1 | 122 (55) | 85 (38) | 14 (6) | Southern Texas | Wide range of mammals, Birds | None |
| Ixodes muris | 213 | <0.1 | 27 (66) | 13 (32) | 1 (2) | Eastern | Rodents, Shrews, Birds | Borrelia burgdorferi s.s. |
| Ixodes dentatus | 165 | <0.1 | 7 (7) | 91 (92) | 2 (2) | Eastern | Lagomorphs, Birds | Borrelia burgdorferi s.s. |
| Ixodes angustus | 132 | <0.1 | 53 (72) | 21 (28) | 0 (0) | Widely in the US | Rodents, Shrews, Carnivores | Borrelia burgdorferi s.s. |
| Ixodes spinipalpis | 110 | <0.1 | 13 (28) | 34 (72) | 0 (0) | Western | Rodents, Lagomorphs, Birds | Borrelia burgdorferi s.s. |
| Amblyomma tuberculatum | 109 | <0.1 | 0 (0) | 0 (0) | 109 (100) | Southeastern | Tortoises | None |
| Haemaphysalis longicornis e | 32 | <0.1 | 2 (9) | 3 (13) | 18 (78) | Eastern | Ungulates, Carnivores, Birds | Under investigation |
| Haemaphysalis leporispalustris | 30 | <0.1 | 1 (17) | 5 (83) | 0 (0) | Widely in the US | Lagomorphs | None |
| Dermacentor hunteri | 25 | <0.1 | 24 (96) | 1 (4) | 0 (0) | Southwestern | Ungulates (wild sheep) | None |
| Amblyomma triste | 9 | <0.1 | 9 (100) | 0 (0) | 0 (0) | Arizona/Texas | Wide range of mammals, Birds | Rickettsia parkeri |
| Dermacentor parumapertus | 7 | <0.1 | 5 (71) | 2 (29) | 0 (0) | Western | Lagomorphs | None |
| Ixodes texanus | 6 | <0.1 | 1 (17) | 0 (0) | 5 (83) | Widely in the US | Rodents, Lagomorphs, Carnivores | None |
| Amblyomma tenellum b | 5 | <0.1 | 2 (50) | 2 (50) | 0 (0) | Southern Texas | Wide range of mammals, Birds | None |
| Haemaphysalis chordeilis | 5 | <0.1 | 1 (100) | 0 (0) | 0 (0) | Widely in the US | Birds | None |
| Ixodes kingi | 5 | <0.1 | 1 (25) | 3 (75) | 0 (0) | Widely in the US | Rodents, Carnivores | None |
| Ixodes sculptus | 5 | <0.1 | 1 (25) | 3 (75) | 0 (0) | Widely in the US | Rodents, Carnivores | None |
| Amblyomma inornatum | 4 | <0.1 | 1 (100) | 0 (0) | 0 (0) | Southern Texas | Wide range of mammals, Birds | None |
| Ixodes woodi | 3 | <0.1 | 0 (0) | 2 (100) | 0 (0) | Widely in the US | Rodents | None |
| Rhipicephalus annulatus b | 3 | <0.1 | 3 (100) | 0 (0) | 0 (0) | Southern Texas | Ungulates | None |
| Ixodes affinis | 2 | <0.1 | — | — | — | Southeastern | Wide range of mammals, Birds | Borrelia burgdorferi s.s. |
| Ixodes banksi | 2 | <0.1 | 1 (100) | 0 (0) | 0 (0) | Eastern | Rodents | None |
| Ixodes baergi | 1 | <0.1 | — | — | — | Eastern | Birds | None |
| Ixodes brunneus | 1 | <0.1 | 1 (100) | 0 (0) | 0 (0) | Widely in the US | Birds | None |
| Ixodes rugosus | 1 | <0.1 | 1 (100) | 0 (0) | 0 (0) | Far Western | Carnivores | None |
Based on taxonomic nomenclature presented by Guglielmone et al. (2014, 2020), Nava et al. (2014a, 2014b, 2015), and Guglielmone and Robbins (2018).
Including synonyms for the following species: Amblyomma tenellum (=Amblyomma imitator); Dermacentor albipictus (=Dermacentor nigrolineatus); Dermacentor andersoni (=Dermacentor venustus); Ixodes cookei (=Ixodes cruciarius); Ixodes pacificus (=Ixodes ricinus californicus, Ixodes californicus); Ixodes scapularis (=Ixodes ricinus scapularis, Ixodes dammini); and Rhipicephalus annulatus (=Margaropus annulatus, Boophilus annulatus).
Records for Dermacentor variabilis in the far western US may in part or entirely represent the recently described Dermacentor similis n. sp. (Lado et al., 2021).
As noted by Nava et al. (2014a, 2015) and Guglielmone and Robbins (2018), there are unresolved questions regarding species within the Rhipicephalus sanguineus sensu lato and Amblyomma cajennense sensu lato complexes, including identification of Am. cajennense versus Amblyomma mixtum in the US, and data for these two closely related species are therefore presented as Am. cajennense s.l. Guglielmone et al. (2020) consider Am. mixtum to be the only member of the Am. cajennense s.l. complex established in the US.
The invasive Haemaphysalis longicornis is now established in the US and therefore merits inclusion here. Additional records of human infestation not yet presented in the peer-reviewed literature are included in the United States Department of Agriculture, National Haemaphysalis longicornis (Asian longhorned tick) Situation Report (https://www.aphis.usda.gov/animal_health/animal_diseases/tick/downloads/longhorned-tick-sitrep.pdf).
All life stages combined, based on data presented in Supplementary Tables 1–36. Percentages refer to contribution to human encounters across tick species. The data refer broadly to human tick encounters, as not all publications make it clear if ticks recorded to infest humans were biting or still crawling on clothing or skin.
Excluding specimens for which life stage was not defined (see Supplementary Tables 1–36). Percentages refer to contribution to human encounters across life stages for a given tick species.
Borrelia burgdorferi sensu stricto.