Where in the world are encephalitis‑carrying ticks found? - briefly
Encephalitis‑vector ticks inhabit temperate regions of Europe, Asia, and North America. High‑risk zones include the Baltic states, Siberian Russia, the United Kingdom, and the northeastern United States, where species such as Ixodes ricinus and I. scapularis are common.
Where in the world are encephalitis‑carrying ticks found? - in detail
Encephalitis‑transmitting ticks are concentrated in temperate and sub‑tropical zones across several continents. In Europe, the castor‑bean tick (Ixodes ricinus) and the taiga tick (Ixodes persulcatus) serve as primary vectors for tick‑borne encephalitis (TBE) virus. Their range extends from the British Isles and Scandinavia through Central Europe to the Baltic states, Poland, the Czech Republic, and into western Russia. In the Russian Far East and Siberia, I. persulcatus dominates, reaching the Ural Mountains and the Altai region.
In Asia, TBE‑competent Ixodes species inhabit the Korean Peninsula, northern Japan (Hokkaido), and the mountainous areas of China’s Heilongjiang and Jilin provinces. The Himalayan region hosts Haemaphysalis longicornis, which can transmit the related severe fever with thrombocytopenia syndrome virus, occasionally associated with encephalitic presentations.
North America contains two Ixodes species implicated in Powassan virus transmission: the black‑legged tick (Ixodes scapularis) in the eastern United States and the western black‑legged tick (Ixodes pacificus) along the Pacific coast. Recorded foci include the northeastern states (New York, Connecticut, Massachusetts), the Great Lakes region, and parts of the Pacific Northwest (Washington, Oregon). Occasional cases have been documented in the Midwest and southern Canada.
The Indian subcontinent reports Kyasanur Forest disease virus carried by Haemaphysalis spinigera, found in the Western Ghats and adjoining forested districts of Karnataka, Kerala, and Tamil Nadu. Sporadic human encephalitis cases arise from exposure to these ticks.
In Australia, the paralysis tick (Ixodes holocyclus) and the long‑horned tick (Haemaphysalis longicornis) are present along the eastern seaboard and in southern Queensland. While primarily linked to tick‑induced paralysis, they have been identified as carriers of flaviviruses capable of causing encephalitic illness.
Summarized distribution:
- Europe: Ixodes ricinus, Ixodes persulcatus – Britain, Scandinavia, Central and Eastern Europe, western Russia.
- Asia: Ixodes persulcatus, Haemaphysalis longicornis – Korea, Japan (Hokkaido), Siberia, northern China.
- North America: Ixodes scapularis, Ixodes pacificus – northeastern USA, Great Lakes, Pacific Northwest, southern Canada.
- Indian subcontinent: Haemaphysalis spinigera – Western Ghats, Karnataka, Kerala, Tamil Nadu.
- Australia: Ixodes holocyclus, Haemaphysalis longicornis – eastern coast, southern Queensland.
These regions represent the global hotspots where tick species capable of transmitting encephalitic viruses are established.