How many diseases can a tick transmit? - briefly
Ticks can carry and transmit over 30 distinct pathogens, including bacteria, viruses, and protozoa. The precise count depends on geographic region and tick species.
How many diseases can a tick transmit? - in detail
Ticks are vectors for a broad spectrum of pathogens, encompassing bacteria, viruses, protozoa and helminths. Scientific surveys identify more than 30 distinct disease agents that can be transmitted by tick species worldwide, with the exact count varying as new agents are discovered and taxonomic revisions occur.
Key bacterial agents include:
- Borrelia burgdorferi complex (Lyme disease)
- Borrelia miyamotoi (relapsing fever)
- Rickettsia spp. (spotted fevers, typhus)
- Anaplasma phagocytophilum (human granulocytic anaplasmosis)
- Ehrlichia spp. (ehrlichiosis)
- Coxiella burnetii (Q fever)
- Francisella tularensis (tularemia)
Viral pathogens transmitted by ticks comprise:
- Tick-borne encephalitis virus (TBEV)
- Crimean‑Congo hemorrhagic fever virus (CCHFV)
- Powassan virus
- Heartland virus
- Severe fever with thrombocytopenia syndrome virus (SFTSV)
Protozoal infections include:
- Babesia microti and related Babesia spp. (babesiosis)
- Theileria spp. (human theileriosis, rare)
- Hepatozoon spp. (occasionally reported)
Helminthic agents are less common but documented:
- Dirofilaria spp. (subcutaneous dirofilariasis)
- Spirocerca spp. (rare human cases)
Geographic distribution of these diseases aligns with the habitats of their tick vectors. In North America, Ixodes scapularis and Ixodes pacificus dominate transmission of Lyme disease, anaplasmosis and babesiosis. In Europe and Asia, Ixodes ricinus and Ixodes persulcatus spread Lyme disease, TBEV and several rickettsial infections. Dermacentor species in Africa, the Middle East and parts of Europe transmit rickettsial spotted fevers and CCHFV. Hyalomma ticks, prevalent in the Mediterranean basin and Central Asia, are primary vectors for CCHFV and SFTSV.
The cumulative tally of recognized tick‑borne diseases exceeds 30, and ongoing research regularly adds new agents to this list. Surveillance data indicate that the diversity of pathogens is expanding due to ecological changes, wildlife host migrations and increased human exposure to tick habitats.