Table 1. Adult and nymphal Ixodes pacificus and Ixodes spinipalpis collected in California and tested for Borrelia spp., 2008–2015.
| Region | County | Tick species | Life stage | # tested | # samples positive for B. burgdorferi s.l. | % prevalence of B. burgdorferi s.l. | # in subset with B. burgdorferi s.l. genomospecies determined a | B. americana | B. bissettiae | B. burgdorferi ss |
|---|---|---|---|---|---|---|---|---|---|---|
| Central Coast | ||||||||||
| Monterey | Ixodes pacificus | Adult | 140 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 35 | 0 | 0.0 | ||||||
| San Benito | Ixodes pacificus | Adult | 47 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 4 | 0 | 0.0 | ||||||
| San Luis Obispo | Ixodes pacificus | Adult | 298 | 1 | 0.3 | 1 | 1 | |||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Central Valley | ||||||||||
| Colusa | Ixodes pacificus | Adult | 13 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Glenn | Ixodes pacificus | Adult | 171 | 2 | 1.2 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Kern | Ixodes pacificus | Adult | 57 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Sacramento | Ixodes pacificus | Adult | 88 | 3 | 3.4 | |||||
| Ixodes pacificus | Nymphs | 190 | 18 | 9.5 | 1 | 1 | ||||
| Ixodes spinipalpis | Nymphs | 11 | 1 | 9.1 | ||||||
| San Joaquin | Ixodes pacificus | Adult | 13 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 3 | 0 | 0.0 | ||||||
| Stanislaus | Ixodes pacificus | Adult | 211 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Yuba | Ixodes pacificus | Adult | 424 | 7 | 1.7 | |||||
| Ixodes pacificus | Nymphs | 30 | 0 | 0.0 | ||||||
| North Coastal | ||||||||||
| Alameda | Ixodes pacificus | Adult | 466 | 5 | 1.1 | |||||
| Ixodes pacificus | Nymphs | 29 | 0 | 0.0 | ||||||
| Contra Costa | Ixodes pacificus | Adult | 285 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 264 | 4 | 1.5 | 1 | 1 | ||||
| Ixodes spinipalpis | Nymphs | 1 | 0 | 0.0 | ||||||
| Humboldt | Ixodes pacificus | Adult | 30 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 2 | 0 | 0.0 | ||||||
| Lake | Ixodes pacificus | Adult | 253 | 2 | 0.8 | 2 | 2 | |||
| Ixodes pacificus | Nymphs | 492 | 14 | 2.8 | 7 | 7 | ||||
| Marin | Ixodes pacificus | Adult | 682 | 14 | 2.1 | 4 | 1 | 3 | ||
| Ixodes pacificus | Nymphs | 331 | 24 | 7.3 | 10 | 10 | ||||
| Mendocino | Ixodes pacificus | Adult | 61 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 19 | 0 | 0.0 | ||||||
| Napa | Ixodes pacificus | Adult | 385 | 3 | 0.8 | |||||
| Ixodes pacificus | Nymphs | 342 | 3 | 0.9 | ||||||
| San Mateo | Ixodes pacificus | Adult | 620 | 15 | 2.4 | 6 | 1 | 2 | 3 | |
| Ixodes spinipalpis | Adult | 1 | 0 | 0.0 | ||||||
| Ixodes pacificus | Nymphs | 96 | 4 | 4.2 | ||||||
| Ixodes spinipalpis | Nymphs | 5 | 1 | 20.0 | ||||||
| Santa Clara | Ixodes pacificus | Adult | 182 | 3 | 1.6 | 3 | 3 | |||
| Ixodes pacificus | Nymphs | 134 | 9 | 6.7 | 6 | 6 | ||||
| Santa Cruz | Ixodes pacificus | Adult | 893 | 3 | 0.3 | 1 | 1 | |||
| Ixodes pacificus | Nymphs | 476 | 16 | 3.4 | 6 | 1 | 5 | |||
| Ixodes spinipalpis | Nymphs | 4 | 1 | 25.0 | ||||||
| Solano | Ixodes pacificus | Adult | 121 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Sonoma | Ixodes pacificus | Adult | 216 | 1 | 0.5 | |||||
| Ixodes pacificus | Nymphs | 337 | 3 | 0.9 | 1 | 1 | ||||
| Trinity | Ixodes pacificus | Adult | 56 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Sierra-Nevada Foothills | ||||||||||
| Amador | Ixodes pacificus | Adult | 256 | 3 | 1.2 | |||||
| Ixodes pacificus | Nymphs | 116 | 7 | 6.0 | ||||||
| Butte | Ixodes pacificus | Adult | 441 | 8 | 1.8 | 1 | 1 | |||
| Ixodes pacificus | Nymphs | 309 | 17 | 5.5 | 3 | 3 | ||||
| Calaveras | Ixodes pacificus | Adult | 537 | 7 | 1.3 | 1 | 1 | |||
| Ixodes pacificus | Nymphs | 30 | 0 | 0.0 | ||||||
| El Dorado | Ixodes pacificus | Adult | 312 | 10 | 3.2 | 5 | 5 | |||
| Ixodes pacificus | Nymphs | 233 | 21 | 9.0 | 2 | 2 | ||||
| Ixodes spinipalpis | Nymphs | 12 | 3 | 25.0 | ||||||
| Inyo | Ixodes pacificus | Adult | 2 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Mariposa | Ixodes pacificus | Adult | 181 | 1 | 0.6 | 1 | 1 | |||
| Ixodes pacificus | Nymphs | 15 | 0 | 0.0 | ||||||
| Nevada | Ixodes pacificus | Adult | 551 | 7 | 1.3 | 1 | 1 | |||
| Ixodes pacificus | Nymphs | 173 | 6 | 3.5 | ||||||
| Placer | Ixodes pacificus | Adult | 10 | 1 | 10.0 | |||||
| Ixodes pacificus | Nymphs | 40 | 0 | 0.0 | ||||||
| Shasta | Ixodes pacificus | Adult | 460 | 26 | 5.7 | |||||
| Ixodes pacificus | Nymphs | 90 | 0 | 0.0 | ||||||
| Sierra | Ixodes pacificus | Adult | 28 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Siskiyou | Ixodes pacificus | Adult | 13 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Tuolumne | Ixodes pacificus | Adult | 64 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 3 | 0 | 0.0 | ||||||
| Southern Region | ||||||||||
| Los Angeles | Ixodes pacificus | Adult | 360 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 11 | 0 | 0.0 | ||||||
| Orange | Ixodes pacificus | Adult | 659 | 2 | 0.3 | |||||
| Ixodes spinipalpis | Adult | 4 | 1 | 25.0 | 1 | 1 | ||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Ixodes spinipalpis | Nymphs | 111 | 20 | 18.0 | 8 | 2 | 6 | |||
| Riverside | Ixodes pacificus | Adult | 180 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 1 | 0 | 0.0 | ||||||
| San Bernardino | Ixodes pacificus | Adult | 678 | 3 | 0.4 | |||||
| Ixodes pacificus | Nymphs | 1 | 0 | 0.0 | ||||||
| San Diego | Ixodes pacificus | Adult | 58 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
| Santa Barbara | Ixodes pacificus | Adult | 496 | 1 | 0.2 | |||||
| Ixodes pacificus | Nymphs | 9 | 0 | 0.0 | ||||||
| Ventura | Ixodes pacificus | Adult | 68 | 0 | 0.0 | |||||
| Ixodes pacificus | Nymphs | 0 | 0 | |||||||
a Due to screening a subset of samples positive for B. burgdorferi s.l., a true prevalence of genospecies by county could not be determined.