How do ticks infect people? - briefly
Ticks attach to skin, insert their mouthparts, and transmit pathogens present in their salivary glands during blood feeding. Infection occurs when the tick remains attached long enough for the pathogen to enter the host’s bloodstream.
How do ticks infect people? - in detail
Ticks become vectors for human disease through a series of biological steps that begin when an unfed nymph or adult attaches to the skin and ends with the inoculation of pathogens during blood ingestion. The process can be divided into acquisition, maintenance, and transmission phases.
During the acquisition phase, a tick feeds on an infected reservoir host—commonly small mammals, birds, or deer. While the mouthparts pierce the host’s skin, the tick inserts its hypostome and secretes saliva containing anticoagulants and immunomodulatory proteins. Pathogens present in the host’s blood enter the tick’s midgut, where they survive, multiply, or undergo developmental changes. Many agents, such as Borrelia burgdorferi (Lyme disease) and Anaplasma phagocytophilum (anaplasmosis), colonize the midgut epithelium before migrating to other tissues.
In the maintenance phase, the pathogen persists within the tick through molting stages (transstadial transmission). The tick’s internal environment, including the salivary glands, provides a niche for the organism. Some bacteria, viruses, and protozoa can also be transmitted from the female to her offspring (transovarial transmission), ensuring the next generation carries the infectious agent.
Transmission to a human host occurs during the feeding episode. As the tick’s salivary glands become active, the pathogen is released into the saliva and injected into the bite site. The timing of transmission varies by pathogen:
- Borrelia spp. typically require ≥24 hours of attachment before efficient transfer.
- Rickettsia rickettsii (Rocky Mountain spotted fever) can be transmitted within a few hours.
- Powassan virus may be transferred in less than 15 minutes of feeding.
Factors influencing infection risk include tick species, life stage, ambient temperature, and host grooming behavior. Nymphs, being small and often unnoticed, contribute disproportionately to human cases despite lower pathogen loads than adults.
Effective control focuses on preventing attachment and prompt removal. Regular inspection of skin and clothing, use of repellents containing DEET or picaridin, and habitat management to reduce tick populations lower exposure. Early removal—grasping the tick close to the skin with fine‑tipped tweezers and extracting without crushing—reduces the window for pathogen transmission.
Understanding each stage of the tick‑borne transmission cycle informs public‑health strategies aimed at reducing the incidence of diseases such as Lyme disease, anaplasmosis, babesiosis, and tick‑borne encephalitis.