What does a tick infected with Borrelia look like? - briefly
An infected tick looks the same as a healthy one: a dark, oval arachnid measuring 2–5 mm when unfed and expanding to about 10 mm after feeding. Visual differences are unreliable, so laboratory testing is required for confirmation.
What does a tick infected with Borrelia look like? - in detail
An infected tick can be identified by several observable traits that differ from an uninfected specimen. The adult Ixodes species typically measures 2–3 mm when unfed; after a blood meal it expands to 5–6 mm and becomes noticeably engorged. Infected individuals often display a darker, more reddish‑brown dorsal surface compared to the lighter tan of a clean tick. The scutum may appear slightly more opaque, and the ventral plates can show a faint bluish hue due to hemolymph changes.
Microscopic examination reveals additional markers. Under dark‑field illumination, spirochetes resembling « Borrelia burgdorferi » can be observed moving within the tick’s midgut and salivary glands. Polymerase chain reaction (PCR) performed on a small tissue sample confirms the presence of Borrelia DNA, producing a distinct amplification pattern. Fluorescent in‑situ hybridisation (FISH) highlights bacterial clusters as bright green signals against a dark background, confirming infection at the cellular level.
Key visual indicators include:
- Enlarged body size after feeding, exceeding 5 mm in length.
- Darker dorsal coloration with a reddish‑brown tint.
- Slightly opaque scutum and bluish ventral plates.
- Presence of motile spirochetes in midgut when examined by dark‑field microscopy.
- Positive PCR or FISH results indicating Borrelia genetic material.
These characteristics together provide a reliable basis for recognizing a tick carrying the Lyme‑disease pathogen.