What does a tick that transmits encephalitis look? - briefly
A tick capable of transmitting encephalitis, such as the deer tick (Ixodes scapularis), is a small, flat, oval arachnid about 2–3 mm long, dark brown when unfed and turning reddish‑brown and engorged after a blood meal. It has a hard dorsal shield (scutum) and six legs as a larva, expanding to eight legs in the adult stage.
What does a tick that transmits encephalitis look? - in detail
The tick species most commonly associated with encephalitis transmission are members of the genus Ixodes, particularly the deer tick (Ixodes scapularis) in North America and the European castor‑bean tick (Ixodes ricinus) in Europe. Their morphology is distinctive and can be identified with careful examination.
- Size: Adult females range from 3 to 5 mm in length when unfed; males are slightly smaller, 2 to 3 mm. Nymphs measure 1 to 2 mm, while larvae are under 1 mm. Engorged females may expand to 10 mm or more.
- Body shape: The body is divided into two main parts—the anterior capitulum (head) and the posterior idiosoma (body). The capitulum bears the mouthparts: a ventral, forward‑projecting hypostome with rows of backward‑pointing barbs, a pair of chelicerae, and palps.
- Scutum: A hard, shield‑like plate covers the dorsal surface of males and partially covers females. In females, the scutum occupies less than half of the dorsum, leaving space for blood expansion. The scutum is typically dark brown to black, sometimes with lighter markings.
- Legs: Eight legs are present on all stages beyond the larva. Legs are long, slender, and segmented, each ending in a claw that assists in anchoring to host hair or fur. Leg coloration matches the body, ranging from brown to reddish‑brown.
- Eyes: Two simple eyes (ocelli) are situated near the anterior edge of the scutum, visible as small dark spots under magnification.
- Sensory organs: Haller’s organ, located on the first pair of legs, detects carbon dioxide, heat, and host movement, facilitating host‑seeking behavior.
Identification keys often rely on the combination of a flat, oval scutum, a robust hypostome with barbs, and the characteristic “shield” pattern. Engorged females exhibit a markedly swollen abdomen, a key indicator of recent blood feeding and potential pathogen transmission. Accurate visual assessment, supported by magnification tools, enables recognition of ticks capable of transmitting encephalitic viruses such as Powassan, Tick‑borne encephalitis virus, and others.