How to test a tick for Lyme disease? - briefly
Send the tick to a certified laboratory for PCR testing of Borrelia burgdorferi DNA, using a sterile container and appropriate labeling. PCR is the standard method because it detects pathogen DNA rapidly and reliably.
How to test a tick for Lyme disease? - in detail
Testing a tick for the presence of Borrelia burgdorferi involves several distinct phases: specimen collection, preservation, laboratory analysis, and result interpretation.
The first phase requires careful removal of the arthropod. Use fine‑point tweezers to grasp the tick close to the mouthparts and pull upward with steady pressure, avoiding crushing the body. Place the specimen in a sterile, sealable tube or vial. If immediate processing is not possible, store the tick at 4 °C for up to 48 hours or freeze at –20 °C for longer periods; avoid repeated freeze‑thaw cycles as they can degrade DNA.
The second phase concerns sample preparation. In a biosafety cabinet, surface‑sterilize the tick with 70 % ethanol, rinse with sterile water, and air‑dry. Depending on the chosen assay, either dissect the midgut and salivary glands or homogenize the whole organism in a lysis buffer. For nucleic acid extraction, follow the manufacturer’s protocol for a commercial kit, ensuring inclusion of a negative extraction control.
The third phase is the analytical method. Commonly employed techniques include:
- Polymerase chain reaction (PCR) – targets conserved Borrelia genes such as flab, ospA, or 16S rRNA. Real‑time PCR provides quantitative data and reduces contamination risk.
- Reverse transcription PCR (RT‑PCR) – detects messenger RNA, indicating viable organisms.
- Nested PCR – increases sensitivity for low‑level infections but requires strict contamination controls.
- Sequencing of PCR amplicons – confirms species identity and can reveal strain variation.
- Immunofluorescence assay (IFA) – uses labeled antibodies to visualize spirochetes in tick tissues, useful for corroborating molecular results.
Quality assurance mandates inclusion of positive, negative, and internal amplification controls in each run. Record cycle threshold (Ct) values for real‑time assays; Ct < 35 generally signifies detectable DNA, whereas higher values may represent background noise.
The final phase interprets the data. A positive molecular result confirms that the tick carried B. burgdorferi at the time of collection, but it does not predict transmission risk to a host. Negative findings do not rule out infection entirely, as low bacterial loads or sampling errors can yield false negatives. Reporting should include assay type, target gene, Ct value, and any sequencing confirmation.
By adhering to these procedures—precise removal, appropriate preservation, rigorous nucleic acid extraction, validated molecular testing, and careful result interpretation—laboratories can reliably assess ticks for Lyme‑causing spirochetes.