The organisms tick vectors transmit. Each row links to the canonical pathogen page — vectors, county-level presence, and the diseases each one causes.
| Scientific name | One-liner | |||
|---|---|---|---|---|
| Anaplasma phagocytophilum | Anaplasma phagocytophilum | Intracellular bacterium that causes anaplasmosis (formerly human granulocytic ehrlichiosis); carried by Ixodes scapularis and I. pacificus. | 2 | 1 |
| Babesia microti | Babesia microti | Malaria-like protozoan that infects red blood cells; the dominant cause of human babesiosis in the northeastern and upper-midwest US. | 1 | 1 |
| Borrelia burgdorferi | Borrelia burgdorferi sensu stricto | Spirochete that causes Lyme disease in the eastern US (carried by Ixodes scapularis) and on the west coast (carried by Ixodes pacificus). | 2 | 1 |
| Borrelia mayonii | Borrelia mayonii | Lyme-disease-causing spirochete first identified in 2013 in upper-midwest deer ticks; produces a distinctive diffuse rash and high spirochetal load. | 1 | 1 |
| Borrelia miyamotoi | Borrelia miyamotoi | Relapsing-fever spirochete carried by Ixodes ticks; causes hard-tick relapsing fever (HTRF) — fever, headache, myalgia without the Lyme bullseye rash. | 1 | 1 |
| Ehrlichia muris eauclairensis | Ehrlichia muris eauclairensis | Upper-midwest Ehrlichia variant first identified in Wisconsin/Minnesota in 2009; causes a fever-and-headache illness similar to other ehrlichioses. | 1 | — |
| Powassan virus | Powassan virus | Tick-borne flavivirus transmitted by Ixodes scapularis (deer tick virus, lineage II) and I. cookei; causes severe encephalitis with high case fatality. | 1 | 1 |