What can a tick transmit? - briefly
Ticks transmit a range of pathogens—including bacteria such as Borrelia burgdorferi (Lyme disease) and Anaplasma phagocytophilum, protozoa like Babesia microti, and viruses such as Powassan virus. These agents cause illnesses from Lyme disease and anaplasmosis to babesiosis and viral encephalitis.
What can a tick transmit? - in detail
Ticks act as vectors for a wide range of infectious agents, including bacteria, viruses, protozoa and, in rare cases, fungi. The most clinically significant organisms are listed below, grouped by pathogen type.
-
Bacterial agents
- Borrelia burgdorferi complex – cause Lyme disease; transmitted primarily by Ixodes scapularis and Ixodes ricinus.
- Anaplasma phagocytophilum – responsible for human granulocytic anaplasmosis; common in Ixodes species.
- Ehrlichia chaffeensis – agent of human monocytic ehrlichiosis; transmitted by Amblyomma americanum.
- Rickettsia rickettsii – Rocky Mountain spotted fever pathogen; vectors include Dermacentor andersoni and Dermacentor variabilis.
- Rickettsia parkeri – causes a milder spotted fever; transmitted by Amblyomma maculatum.
- Coxiella burnetii – occasional tick‑borne transmission of Q fever; various hard ticks serve as reservoirs.
-
Viral agents
- Tick‑borne encephalitis virus (TBEV) – flavivirus causing encephalitis; transmitted by Ixodes ricinus and Ixodes persulcatus.
- Crimean‑Congo hemorrhagic fever virus (CCHFV) – nairovirus leading to severe hemorrhagic disease; Hyalomma spp. act as vectors.
- Powassan virus – flavivirus associated with encephalitis; Ixodes cookei and Ixodes scapularis are primary carriers.
- Severe fever with thrombocytopenia syndrome virus (SFTSV) – phlebovirus endemic in East Asia; transmitted by Haemaphysalis longicornis.
-
Protozoan agents
- Babesia microti – cause of babesiosis; Ixodes scapularis transmits the parasite in North America.
- Babesia divergens – European babesiosis; Dermacentor reticulatus serves as vector.
- Theileria spp. – tick‑borne theileriosis affecting livestock; various Dermacentor and Rhipicephalus species.
-
Fungal agents
- Histoplasma capsulatum – rare reports of tick‑associated transmission; not a primary vector but possible mechanical carrier.
In addition to these pathogens, ticks can harbor and transmit multiple agents simultaneously, creating co‑infection scenarios that complicate diagnosis and treatment. Transmission mechanisms differ among pathogen groups: bacterial and protozoan organisms typically migrate from the tick’s salivary glands into the host during feeding, whereas viruses may be secreted in saliva or introduced via regurgitation. The likelihood of transmission increases with longer attachment times; many agents require at least 24–48 hours of feeding before reaching infectious doses.
Preventive measures focus on avoiding tick bites, prompt removal of attached ticks, and, where appropriate, vaccination (e.g., TBEV vaccines) or prophylactic antibiotics for high‑risk exposures. Awareness of regional tick species and their associated pathogen profiles is essential for accurate risk assessment and timely clinical intervention.