What blood tests should be performed after a tick bite?

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What blood tests should be performed after a tick bite? - briefly
Recommended tests include serology for Borrelia burgdorferi (ELISA with confirmatory Western blot) and, when indicated, PCR or serology for Anaplasma, Ehrlichia, and Babesia. A complete blood count should also be performed to identify possible cytopenias.

What blood tests should be performed after a tick bite? - in detail
After a tick attachment, clinicians must assess the risk of vector‑borne infections through targeted serologic and molecular assays. The choice of investigations depends on the geographic region, the duration of attachment, and the tick species involved.

Borrelia burgdorferi (Lyme disease)

Enzyme‑linked immunosorbent assay (ELISA) for IgM and IgG antibodies.
Confirmatory Western blot if ELISA is positive or equivocal.
Polymerase chain reaction (PCR) on blood or tissue samples when early disseminated disease is suspected.

Anaplasma phagocytophilum (human granulocytic anaplasmosis)

Real‑time PCR for bacterial DNA in whole blood, preferred within the first week of illness.
Indirect immunofluorescence assay (IFA) for IgG antibodies, performed convalescent‑phase (2–4 weeks after exposure) to confirm seroconversion.

Ehrlichia chaffeensis (human monocytic ehrlichiosis)

PCR on whole blood for early detection.
IFA for IgG antibodies, with paired sera collected 2–4 weeks apart.

Babesia microti (babesiosis)

Thick‑blood‑smear microscopy for intra‑erythrocytic parasites.
PCR for Babesia DNA, more sensitive in low‑parasitemia cases.
Indirect immunofluorescence for IgG antibodies, useful for retrospective diagnosis.

Rickettsia spp. (spotted fever group)

PCR on whole blood or tissue biopsies during acute phase.
IFA for IgG antibodies, paired samples required for definitive diagnosis.

Tick‑borne encephalitis virus (TBEV)

ELISA for IgM and IgG antibodies in serum or cerebrospinal fluid.
Neutralization test for confirmation if needed.

Hepatitis C virus (rarely transmitted by ticks)

Anti‑HCV antibody test and HCV RNA PCR only if epidemiologic risk factors exist.

Additional laboratory parameters aid clinical evaluation:

Complete blood count with differential – leukopenia, thrombocytopenia, or anemia may indicate specific infections.
Liver function tests – elevated transaminases are common in anaplasmosis, ehrlichiosis, and babesiosis.
Serum creatinine – assess renal involvement, particularly in severe babesiosis.
C‑reactive protein and erythrocyte sedimentation rate – nonspecific markers of inflammation.

Timing of specimen collection is critical. Molecular tests (PCR) provide the highest sensitivity within the first 7–10 days post‑exposure, whereas serologic assays become reliable after seroconversion, typically 2–3 weeks later. Paired serology (acute and convalescent samples) remains the gold standard for confirming many tick‑borne diseases when PCR results are negative or unavailable.
In practice, clinicians often order a panel that includes PCR for Borrelia, Anaplasma, Ehrlichia, and Babesia, combined with serology for Lyme disease, ehrlichiosis, anaplasmosis, and TBEV, adjusting the list based on patient history and regional pathogen prevalence.