What does a tick transmit when it bites? - briefly
Ticks inject saliva containing microorganisms such as Borrelia bacteria (Lyme disease), Rickettsia species (spotted fevers), Anaplasma and Ehrlichia (anaplasmosis, ehrlichiosis), and protozoa like Babesia (babesiosis). These pathogens are transmitted directly into the host’s bloodstream during feeding.
What does a tick transmit when it bites? - in detail
A feeding tick introduces a complex mixture of biologically active substances into the host’s skin. The primary components are saliva proteins that suppress immune responses, prevent blood clotting, and facilitate prolonged attachment. Embedded within this saliva are a variety of infectious agents that can be transferred to the blood stream.
Pathogens commonly transmitted by hard ticks (Ixodidae):
- Spirochetes – Borrelia burgdorferi complex, the cause of Lyme disease; transmitted mainly by Ixodes scapularis and Ixodes ricinus after 36–48 hours of attachment.
- Rickettsiae – Rickettsia rickettsii (Rocky Mountain spotted fever) and Rickettsia parkeri; delivered by Dermacentor species within a few hours.
- Anaplasmataceae – Anaplasma phagocytophilum (human granulocytic anaplasmosis) and Ehrlichia chaffeensis (Ehrlichiosis); require 24–48 hours of feeding.
- Protozoa – Babesia microti (babesiosis) and Babesia divergens; transmitted by Ixodes ticks, typically after 48 hours.
- Flaviviruses – Powassan virus; can be transferred within 15 minutes of attachment.
- Other bacteria – Francisella tularensis (tularemia) and Coxiella burnetii (Q fever); occasional transmission by various tick species.
- Relapsing fever spirochetes – Borrelia miyamotoi; transmitted similarly to Lyme‑causing spirochetes.
Key factors influencing transmission:
- Tick species and life stage – Nymphs often carry higher infection rates than larvae; adults may transmit different agents.
- Geographic distribution – Presence of specific pathogens follows the range of the vector species.
- Duration of attachment – Most bacteria require at least 24 hours of feeding; viruses such as Powassan may be transmitted almost immediately.
- Host immune status – Immunocompromised individuals experience more severe disease courses.
In addition to infectious agents, tick saliva can provoke local inflammation, allergic reactions, and, in rare cases, tick‑borne paralysis caused by neurotoxins from Ixodes holocyclus. Understanding the temporal dynamics of pathogen delivery and the ecological context of tick populations is essential for accurate risk assessment and timely medical intervention.