What can ticks transmit to humans? - briefly
Ticks transmit a range of pathogens—bacterial agents such as Borrelia burgdorferi (Lyme disease), Anaplasma phagocytophilum, Rickettsia species; viral agents including Powassan virus and tick‑borne encephalitis virus; and protozoan parasites like Babesia microti. These infections can produce illnesses from Lyme disease and anaplasmosis to viral encephalitis and babesiosis.
What can ticks transmit to humans? - in detail
Ticks serve as biological vectors that inject pathogens while feeding on blood. The organisms transmitted include bacteria, viruses, protozoa, and, in rare cases, toxins that can affect human health.
Bacterial agents
- Borrelia burgdorferi complex – causes Lyme disease; early signs include erythema migrans, fever, headache; later stages may involve arthritis, neurologic deficits. Primarily transmitted by Ixodes scapularis and Ixodes pacificus in North America, Ixodes ricinus in Europe.
- Anaplasma phagocytophilum – responsible for human granulocytic anaplasmosis; symptoms are fever, leukopenia, thrombocytopenia, elevated liver enzymes. Vector: Ixodes spp.
- Ehrlichia chaffeensis – causes human monocytic ehrlichiosis; fever, rash, hepatitis, and possible severe complications. Transmitted by the lone‑star tick (Amblyomma americanum).
- Rickettsia rickettsii – agent of Rocky Mountain spotted fever; high fever, rash, vascular injury. Vector: American dog tick (Dermacentor variabilis) and Rocky Mountain wood tick (Dermacentor andersoni).
- Rickettsia parkeri – causes a milder spotted fever; transmitted by the Gulf Coast tick (Amblyomma maculatum).
- Francisella tularensis – causes tularemia; ulceroglandular form is most common after tick bite. Vectors include Dermacentor and Amblyomma species.
- Borrelia miyamotoi – relapsing fever–type illness; transmitted by Ixodes ticks, produces recurrent fever, headache, and fatigue.
Viral agents
- Tick‑borne encephalitis virus (TBEV) – flavivirus causing meningitis, encephalitis, or meningoencephalitis; endemic in Europe and Asia; vectors: Ixodes ricinus, Ixodes persulcatus.
- Crimean‑Congo hemorrhagic fever virus (CCHFV) – Nairovirus producing severe hemorrhagic fever; transmitted by Hyalomma ticks across Africa, Asia, and Eastern Europe.
- Heartland virus – phlebovirus associated with fever, leukopenia, and thrombocytopenia; vector: Amblyomma americanum in the United States.
- Bourbon virus – another phlebovirus; causes fever, myalgia, and sometimes severe disease; also linked to Amblyomma americanum.
Protozoal agents
- Babesia microti – causes babesiosis; hemolytic anemia, fever, chills; transmitted by Ixodes scapularis in the northeastern United States. Co‑infection with Borrelia burgdorferi is common.
- Babesia divergens – European variant; similar clinical picture, transmitted by Ixodes ricinus.
Other health impacts
- Relapsing fever Borrelia species (e.g., Borrelia hermsii) – produce recurring fever spikes; vectors are soft ticks of the genus Ornithodoros.
- Alpha‑gal syndrome – delayed allergic reaction to mammalian meat triggered by a carbohydrate (α‑gal) introduced through the bite of Amblyomma americanum; symptoms include urticaria, angioedema, and anaphylaxis.
- Tick saliva contains anticoagulants and immunomodulatory proteins that can cause localized inflammation and, rarely, allergic reactions.
Co‑transmission of multiple agents during a single bite is documented, especially for Ixodes ticks, which may deliver both Borrelia and Anaplasma or Babesia simultaneously. Prompt identification of the specific pathogen guides appropriate antimicrobial, antiviral, or supportive therapy.