What do ixodid ticks carry? - briefly
Hard ticks transmit a variety of pathogens, including the spirochete Borrelia burgdorferi, the bacterium Anaplasma phagocytophilum, Babesia protozoa, and viruses such as tick‑borne encephalitis virus and Crimean‑Congo hemorrhagic fever virus. They also act as reservoirs for several Rickettsia species.
What do ixodid ticks carry? - in detail
Hard ticks serve as vectors for a broad spectrum of disease‑causing agents. Their salivary glands and midgut harbor microorganisms that can be transmitted to vertebrate hosts during blood feeding.
Bacterial agents commonly associated with these arthropods include:
- Borrelia burgdorferi sensu lato complex, the causative agent of Lyme disease.
- Anaplasma phagocytophilum, responsible for human granulocytic anaplasmosis.
- Ehrlichia spp., such as E. chaffeensis, which cause human monocytic ehrlichiosis.
- Rickettsia spp., notably R. rickettsii (Rocky Mountain spotted fever) and R. conorii (Mediterranean spotted fever).
- Coxiella burnetii, the pathogen of Q fever, occasionally detected in tick populations.
Viral pathogens transmitted by hard ticks comprise:
- Tick‑borne encephalitis virus (TBEV), a flavivirus prevalent in Eurasia.
- Crimean‑Congo hemorrhagic fever virus (CCHFV), a nairovirus with high mortality rates.
- Powassan virus, a flavivirus emerging in North America.
- Heartland virus and SFTS virus, both phleboviruses linked to severe febrile illness.
Protozoan parasites carried by these vectors include:
- Babesia microti and related species, which cause babesiosis.
- Theileria spp., responsible for theileriosis in livestock.
- Hepatozoon spp., parasites of reptiles and mammals.
Non‑infectious substances transferred during feeding are also noteworthy. Tick saliva contains:
- Anticoagulant proteins that prevent clot formation.
- Immunomodulatory molecules that suppress host inflammatory responses.
- Neurotoxic peptides that can induce paralysis in susceptible hosts.
- Allergenic proteins that trigger hypersensitivity reactions in humans and animals.
Geographic distribution influences the specific pathogen assemblage. For example, Ixodes scapularis in North America predominantly transmits Borrelia burgdorferi, while Dermacentor marginatus in Europe is more frequently associated with Rickettsia conorii. Species‑specific feeding habits and host preferences shape the epidemiological risk posed by each tick population.
Transmission occurs primarily through the inoculation of infected salivary secretions into the host skin. Some agents, such as Rickettsia spp., may also be passed transovarially from adult females to offspring, ensuring persistence within tick colonies independent of vertebrate reservoirs.
Understanding the diversity of agents carried by hard ticks is essential for accurate diagnosis, effective treatment, and the development of preventive measures, including vaccines and targeted acaricide strategies.