Tick-borne encephalopathies : epidemiology, diagnosis, treatment and prevention.
Tick-borne encephalopathies constitute a broad range of infectious diseases affecting the brain and other parts of the CNS. The causative agents are both viral and bacterial. This review focuses on the current most important tick-borne human diseases: tick-borne encephalitis (TBE; including Powassan encephalitis) and Lyme borreliosis. Rocky Mountain spotted fever (RMSF) and Colorado tick fever (CTF), less common tick-borne diseases associated with encephalopathy, are also discussed. TBE is the most important flaviviral infection of the CNS in Europe and Russia, with 10 000-12 000 people diagnosed annually. The lethality of TBE in Europe is 0.5% and a post-encephalitic syndrome is seen in over 40% of affected patients, often producing a pronounced impairment in quality of life. There is no specific treatment for TBE. Two vaccines are available to prevent infection. Although these have a good protection rate and good efficacy, there are few data on long-term immunity. Lyme borreliosis is the most prevalent tick-borne disease in Europe and North America, with >50 000 cases annually. Localised early disease can be treated with oral phenoxymethylpenicillin (penicillin V), doxycycline or amoxicillin. The later manifestations of meningitis, arthritis or acrodermatitis can be treated with oral doxycycline, oral amoxicillin or intravenous ceftriaxone; intravenous benzylpenicillin (penicillin G) or cefotaxime can be used as alternatives. The current use of vaccines against Lyme borreliosis in North America is under discussion, as the LYMErix vaccine has been withdrawn from the market because of possible adverse effects, for example, arthritis. RMSF and CTF appear only in North America. RMSF is an important rickettsial disease and is effectively treated with doxycycline. There is no treatment or preventative measure available for CTF.