How does a tick infected with encephalitis look? - briefly
An encephalitis‑carrying tick exhibits no unique external features and looks like a normal engorged or unfed ixodid with typical coloration. Diagnosis relies on laboratory testing, because visual inspection cannot reliably indicate infection.
How does a tick infected with encephalitis look? - in detail
Ticks that carry encephalitic viruses display the same basic morphology as uninfected specimens: a dorsoventral flattening, a hard scutum covering the dorsal surface, eight legs in the adult stage, and a mouth‑part apparatus (capitulum) adapted for blood feeding. Size varies with feeding status; unfed nymphs measure 1–2 mm, while engorged adults can reach 5–7 mm in length.
External characteristics that may suggest viral carriage include:
- Slightly increased abdominal girth compared with unfed individuals of the same stage, reflecting early blood intake that often precedes visible engorgement.
- Darkening of the cuticle, especially on the ventral side, caused by hemoglobin accumulation and oxidative changes in the tick’s hemolymph.
- Presence of a faint, translucent “halo” around the mouthparts, indicating prolonged attachment and potential pathogen migration.
Microscopic examination reveals additional markers:
- Viral antigens detectable by immunofluorescence within the salivary glands and midgut epithelium.
- Cytopathic alterations such as vacuolation of glandular cells and disrupted basal lamina structures.
- Accumulation of viral particles in the acini of the salivary glands, observable under electron microscopy as 50‑nm enveloped virions.
Practical identification relies on a combination of visual assessment and laboratory confirmation. Visual screening focuses on the size, coloration, and abdominal distension described above, while definitive diagnosis requires molecular techniques (reverse‑transcriptase PCR) or antigen detection assays applied to tick homogenates.