What can a tick be infected with? - briefly
Ticks may carry bacterial agents such as Borrelia burgdorferi, Anaplasma phagocytophilum, and Rickettsia species, viral agents including Powassan virus and tick‑borne encephalitis virus, and protozoan parasites like Babesia microti. These pathogens can be transmitted to humans and animals during blood feeding.
What can a tick be infected with? - in detail
Ticks serve as vectors for a wide range of microorganisms that cause human and animal disease. The most common groups include bacteria, viruses, protozoa and, less frequently, filarial worms.
Bacterial agents transmitted by hard ticks encompass:
- Borrelia burgdorferi, the causative organism of Lyme disease; infection typically follows a bite from Ixodes species and may produce erythema migrans, arthritis and neurologic involvement.
- Borrelia miyamotoi, responsible for a relapsing‑fever syndrome; symptoms resemble those of Lyme disease but often include high fever and chills.
- Anaplasma phagocytophilum, which causes human granulocytic anaplasmosis; clinical picture features fever, leukopenia and elevated liver enzymes.
- Ehrlichia chaffeensis and Ehrlichia ewingii, agents of human monocytic and granulocytic ehrlichiosis respectively; presentation includes fever, headache and rash.
- Rickettsia rickettsii, the pathogen of Rocky Mountain spotted fever; transmitted by Dermacentor ticks, it produces petechial rash, fever and potential multiorgan failure.
- Rickettsia parkeri, associated with a milder spotted fever; infection manifests as fever, eschar at the bite site and a localized rash.
- Coxiella burnetii, the agent of Q fever; occasional transmission occurs through tick bites, leading to fever, pneumonia and hepatitis.
Protozoal pathogens include:
- Babesia microti, causing babesiosis; intra‑erythrocytic parasites lead to hemolytic anemia, fever and chills, especially in immunocompromised individuals.
- Babesia divergens, less common in humans but documented in Europe; infection resembles malaria with high parasitemia and severe anemia.
Viral agents transmitted by ticks are fewer but clinically significant:
- Powassan virus, a flavivirus spread by Ixodes ticks; infection may result in encephalitis, meningitis or fatal neurologic disease.
- Tick‑borne encephalitis virus (TBEV), prevalent in Eurasia; two clinical phases involve febrile illness followed by neurological complications such as meningitis, encephalitis or myelitis.
- Crimean‑Congo hemorrhagic fever virus, transmitted by Hyalomma ticks; disease presents with high fever, hemorrhage and high mortality.
Occasional reports describe filarial nematodes such as Dirofilaria species transmitted by ticks, leading to subcutaneous nodules or ocular involvement.
Pathogen prevalence varies with tick species, geographic region and host reservoir. Ixodes ticks dominate in temperate zones, carrying Borrelia, Anaplasma and Babesia. Dermacentor species are primary vectors for Rickettsia rickettsii and Ehrlichia. Hyalomma ticks dominate in arid regions, linked to Crimean‑Congo hemorrhagic fever virus.
Effective prevention relies on avoidance of tick habitats, use of repellents, prompt removal of attached ticks and vaccination where available, such as for tick‑borne encephalitis. Early recognition of disease manifestations and appropriate antimicrobial or antiviral therapy reduce morbidity and mortality.