How does infection from ticks occur? - briefly
Pathogens are transferred to the host when a feeding tick inserts its mouthparts and injects saliva containing the infectious agents. The probability of transmission rises sharply after the tick remains attached for several hours.
How does infection from ticks occur? - in detail
Ticks acquire pathogens while feeding on infected hosts. During the blood meal, the tick’s mouthparts penetrate the skin and create a feeding pool. Saliva, which contains anticoagulants and immunomodulatory compounds, is injected into the host. Pathogens present in the tick’s salivary glands or midgut are released with the saliva, entering the host’s bloodstream.
Transmission mechanisms differ among agents:
- Salivary transmission – most common; bacteria, viruses, and protozoa migrate to the salivary glands and are delivered during feeding.
- Regurgitation – occasional release of gut contents into the feeding site, observed with some rickettsial species.
- Co‑feeding – pathogens move between adjacent ticks feeding simultaneously on the same host, bypassing systemic infection of the host.
- Transstadial passage – pathogen survives through the tick’s developmental stages (larva → nymph → adult), maintaining infectivity.
- Transovarial transmission – infected females pass pathogens to offspring via eggs, ensuring presence in the next generation.
Key factors influencing infection risk include:
- Duration of attachment – most pathogens require several hours of feeding before transmission; for example, Borrelia burgdorferi typically needs ≥ 24 hours, whereas Anaplasma phagocytophilum can be transmitted within 12 hours.
- Tick species and life stage – different species harbor distinct pathogen assemblages; nymphs often pose greater risk due to their small size and prolonged feeding.
- Host immune status – immunocompromised individuals may develop more severe disease following exposure.
After entry, pathogens disseminate via the circulatory system, colonize target tissues, and elicit specific clinical syndromes. Early detection relies on recognizing the characteristic erythema migrans rash for Lyme disease, fever and thrombocytopenia for tick‑borne encephalitis, or hemolytic anemia for babesiosis.
Preventive measures focus on interrupting the feeding process: prompt removal of attached ticks, use of repellents containing DEET or permethrin, avoidance of high‑risk habitats during peak activity periods, and vaccination where available (e.g., tick‑borne encephalitis vaccine).