Tick Surveillance, Water Year 2025-2026
Tick Collections from 2025-2026 Season (November 2025 through May 2026)
District laboratory staff continued field collections of nymphal Ixodes pacificus (Western black-legged ticks) in April. Nymphal ticks are collected by flagging with a white sheet of flannel attached to a wooden dowel, in leaf litter areas or on rocks and fallen logs. Ixodes pacificus ticks will be tested for the presence of Borrelia burgdorferi (the agent of Lyme disease), as well as Borrelia miyamotoi (the agent of hard-tick relapsing fever) and Anaplasma phagocytophilum (the agent of granulocytic anaplasmosis).
Parks surveyed in April include Pedro Point Headlands and Devil’s Slide trail in Pacifica, Wavecrest Open Space in Half Moon Bay, Windy Hill Open Space Preserve in Portola Valley, Huddart Park in Woodside, Laurelwood Park in San Mateo and La Honda Creek Open Space Preserve near La Honda. Additionally, a school in Hillsborough was flagged for nymphal and adult ticks. Surveys of tick nymphs will continue in May and June.
Tick Collections from parks and neighborhoods, 2025-2026 Season (through April 2026)
| Park/Neighborhood | Nearest City/Town | Number of Ix. pacificus adults | Number of Ix. pacificus nymphs |
|---|---|---|---|
| Coal Creek Open Space Preserve | Portola Valley | 437 | - |
| Wunderlich Park | Woodside | 265 | 87 |
| Laurelwood Park | San Mateo | 320 | - |
| Corte de Madera Creek Open Space Preserve | Portola Valley | 12 | - |
| Mills Canyon Wildlife Refuge | Burlingame | 239 | - |
| La Honda Creek Open Space Preserve | La Honda | 254 | - |
| Teague Hill Open Space Preserve | Woodside | 210 | - |
| Ahni Trail | Pacifica | 13 | - |
| Filoli Estate | Redwood City | 245 | 31 |
| Wavecrest Open Space Preserve | Half Moon Bay | 223 | 55 |
| Año Nuevo State Park | Pescadero | 206 | - |
| Pescadero Marsh Natural Preserve | Pescadero | 192 | - |
| Devil's Slide | Pacifica | 224 | - |
| Pedro Point Headlands | Pacifica | 144 | 20 |
| Jasper Ridge Biological Preserve | Portola Valley | 123 | - |
| Burleigh H. Murray Ranch State Park | Half Moon Bay | 20 | - |
| Edgewood County Park | Redwood City | - | 96 |
| Windy Hill Open Space Preserve | Portola Valley | - | 64 |
| Huddart Park | Woodsdie | 79 | |
| Laurelwood Park | San Mateo | 50 |
Page last reviewed: May 11, 2026