What can a tick carry? - briefly
Ticks can harbor bacteria, viruses, and protozoan parasites that cause illnesses such as Lyme disease, Rocky Mountain spotted fever, and babesiosis. They frequently carry more than one pathogen at a time, raising the chance of co‑infection.
What can a tick carry? - in detail
Ticks serve as vectors for a wide spectrum of microorganisms and biologically active compounds. Their capacity to transmit agents stems from the prolonged feeding period, which allows pathogens to move from the tick’s midgut to its salivary glands and then into the host’s bloodstream.
The principal categories of transmissible agents include:
-
Bacterial agents
- Borrelia burgdorferi complex – causative agents of Lyme disease.
- Rickettsia spp. – responsible for spotted fever group rickettsioses.
- Anaplasma phagocytophilum – agent of human granulocytic anaplasmosis.
- Ehrlichia chaffeensis and Ehrlichia ewingii – cause human monocytic and granulocytic ehrlichiosis.
- Coxiella burnetii – occasional tick‑borne source of Q fever.
-
Viral agents
- Tick‑borne encephalitis virus (TBEV) – prevalent in Eurasia.
- Crimean‑Congo hemorrhagic fever virus (CCHFV) – endemic in Africa, the Balkans, the Middle East and Central Asia.
- Powassan virus – emerging pathogen in North America.
- Severe fever with thrombocytopenia syndrome virus (SFTSV) – reported in East Asia.
-
Protozoal agents
- Babesia microti and related Babesia spp. – cause babesiosis, a malaria‑like illness.
- Theileria spp. – affect livestock, occasionally transmitted to humans.
-
Helminths and other parasites
- Dirofilaria spp. – filarial worms occasionally found in ticks, though transmission to humans is rare.
In addition to infectious agents, ticks introduce biologically active substances that influence host physiology:
- Salivary proteins that inhibit blood clotting, suppress immune responses, and facilitate prolonged attachment.
- Anticoagulants and anti‑inflammatory compounds that reduce host detection and promote feeding efficiency.
- Allergenic proteins that can trigger hypersensitivity reactions in some individuals.
The diversity of transmitted agents varies among tick families and species:
- Ixodes ricinus (European castor bean tick) and Ixodes scapularis (black‑legged tick) are primary vectors for Lyme disease, anaplasmosis, and babesiosis in temperate regions.
- Dermacentor variabilis (American dog tick) and Dermacentor marginatus transmit Rocky Mountain spotted fever and Mediterranean spotted fever agents.
- Rhipicephalus sanguineus (brown dog tick) is associated with Rickettsia conorii and Ehrlichia spp. in tropical and subtropical zones.
- Hyalomma spp. serve as principal carriers of Crimean‑Congo hemorrhagic fever virus and certain Theileria species across Africa and Asia.
Geographic distribution, host preference, and ecological conditions shape the risk profile for each pathogen. Surveillance data indicate that expanding tick habitats, driven by climate change and land‑use alterations, increase exposure to these agents in previously unaffected regions.
Understanding the full range of microorganisms and bioactive compounds that ticks can introduce is essential for accurate diagnosis, effective treatment, and the development of preventive measures such as vaccines, repellents, and targeted tick‑control programs.