What is Borrelia transmitted by ticks? - briefly
«Borrelia» is a genus of spiral‑shaped bacteria transferred to humans by the bite of infected Ixodes ticks, where it commonly induces Lyme disease and associated symptoms. The organism resides in the tick’s midgut and moves to the salivary glands during feeding, allowing direct inoculation into the host’s skin.
What is Borrelia transmitted by ticks? - in detail
Borrelia is a genus of helical, Gram‑negative bacteria transmitted to humans through the bite of ixodid ticks. The organisms belong to the spirochete family and are capable of migrating through host tissues, producing a range of systemic infections.
Human‑pathogenic species are grouped in the Borrelia burgdorferi sensu lato complex. Principal members include Borrelia burgdorferi, Borrelia afzelii, Borrelia garinii, and Borrelia spielmanii. Additional tick‑borne Borrelia, such as Borrelia hermsii, cause relapsing fever and are transmitted by soft ticks of the genus Ornithodoros.
The transmission cycle involves three tick stages—larva, nymph, and adult. Larvae acquire infection while feeding on reservoir hosts (small mammals, birds). The pathogen persists through molting (transstadial transmission) and is transmitted to new hosts during subsequent feedings, most commonly by nymphs. Co‑feeding on the same host can also spread infection without systemic host infection.
Geographically, tick‑borne Borrelia is prevalent in temperate zones of North America, Europe, and parts of Asia. Distribution correlates with the presence of competent tick vectors (e.g., Ixodes scapularis, Ixodes ricinus) and suitable wildlife reservoirs. Seasonal activity peaks in late spring and early summer, when nymphal ticks seek blood meals.
Clinical presentation follows a staged progression:
- Early localized disease: erythema migrans at the bite site, accompanied by fever, headache, and myalgia.
- Early disseminated disease: multiple skin lesions, cranial nerve palsies, meningitis, and cardiac conduction abnormalities.
- Late disseminated disease: migratory arthritis, chronic neuropathy, and neurocognitive deficits.
Diagnosis relies on a combination of clinical assessment and laboratory testing. Serological assays (ELISA followed by confirmatory Western blot) detect specific antibodies. Molecular methods such as PCR identify Borrelia DNA in blood, cerebrospinal fluid, or tissue samples. Culture is rarely performed due to low sensitivity.
Recommended antimicrobial regimens include doxycycline (100 mg twice daily for 10–21 days) for most presentations, amoxicillin or cefuroxime axetil for patients unable to tolerate tetracyclines, and intravenous ceftriaxone for severe neurologic or cardiac involvement.
Preventive measures focus on minimizing tick exposure:
- Wear long sleeves and trousers, tucking clothing into socks.
- Apply repellents containing DEET or picaridin to skin and clothing.
- Perform thorough tick checks after outdoor activities and remove attached ticks promptly with fine‑tipped tweezers.
- Manage vegetation around residential areas to reduce tick habitat.
- No licensed vaccine for human use currently exists; research continues.
Understanding the biology, ecology, and clinical impact of tick‑borne Borrelia is essential for effective diagnosis, treatment, and public‑health strategies.