What do encephalitis ticks carry? - briefly
Ticks that cause encephalitis transmit viruses such as the tick‑borne encephalitis virus (TBEV) in Europe and Asia and Powassan virus in North America; certain species also carry Crimean‑Congo hemorrhagic fever virus and other flaviviruses.
What do encephalitis ticks carry? - in detail
Ticks that transmit encephalitic disease agents carry a limited but clinically significant group of viruses and, less commonly, bacteria. The principal viral pathogens are:
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Tick‑borne encephalitis virus (TBEV) – a flavivirus endemic to Central and Eastern Europe and parts of Northern Asia. Two main subtypes exist: the European (Western) strain, which usually produces a biphasic illness with meningitis or encephalitis, and the Siberian strain, associated with more severe neurological damage. The vector is primarily Ixodes ricinus in Europe and Ixodes persulcatus in Asia. Human infection follows a bite from an infected nymph or adult; incubation ranges from 7 to 28 days.
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Powassan virus – a member of the Flaviviridae family, found in North America. Two lineages circulate: the prototype Powassan virus (lineage I) transmitted mainly by Ixodes cookei, and the deer‑tick virus (lineage II) carried by Ixodes scapularis and Ixodes pacificus. Illness onset occurs within 1–5 weeks after exposure; neuroinvasive disease manifests as encephalitis, meningoencephalitis, or acute flaccid paralysis, with a reported case‑fatality rate of 10 % and frequent long‑term neurological sequelae.
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Louping ill virus – a sheep‑associated flavivirus prevalent in the United Kingdom and parts of Europe. The primary vector is Ixodes ricinus. Humans acquire infection through tick bites, producing febrile illness that may progress to encephalitis, especially in children.
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Omsk hemorrhagic fever virus – a Bunyaviridae agent transmitted by Dermacentor spp. in Siberia. Although hemorrhagic manifestations dominate, encephalitic complications have been documented in severe cases.
Bacterial agents occasionally co‑occur with viral infections:
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Borrelia burgdorferi – the Lyme disease spirochete, transmitted by the same Ixodes ticks that carry TBEV. While Lyme neuroborreliosis primarily causes meningoradiculitis, it can present with encephalitic features in rare instances.
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Anaplasma phagocytophilum – the causative organism of human granulocytic anaplasmosis. Neurological involvement is uncommon but may include encephalitis‑like symptoms when the infection spreads systemically.
Key points regarding these pathogens:
- Geographic distribution dictates exposure risk; European and Asian travelers should consider TBEV, while North‑American outdoor workers face Powassan virus.
- Tick life stage influences transmission probability; nymphs, being small and often unnoticed, account for the majority of human bites.
- Seasonality aligns with tick activity peaks: spring and early summer for most species, extending into autumn in milder climates.
- Co‑infection can occur when a single tick harbors multiple agents, complicating diagnosis and treatment.
- Preventive measures—prompt tick removal, use of repellents, and vaccination where available (e.g., TBEV vaccines in Europe and Asia)—reduce the likelihood of acquiring encephalitic disease.