View source for Tick-borne encephalitis

{{Use dmy dates|date=February 2023}}
{{More citations needed|date=January 2010}}
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| name            = Tick-borne meningoencephalitis
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| image           = EurAsia TBE-belt.svg
| caption         = Infected countries/areas in Eurasia
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| field           = [[Infectious disease (speciality)|Infectious disease]]
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'''Tick-borne encephalitis''' ('''TBE''') is a [[virus|viral]] [[infectious disease]] involving the [[central nervous system]]. The disease most often manifests as [[meningitis]], [[encephalitis]] or [[meningoencephalitis]]. [[Myelitis]] and spinal paralysis also occur. In about one third of cases [[sequela]]e, predominantly cognitive dysfunction, persist for a year or more.<ref name=":0">{{Cite journal|last1=Lindquist|first1=Lars|last2=Vapalahti|first2=Olli|date=31 May 2008|title=Tick-borne encephalitis|url=https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(08)60800-4/abstract|journal=The Lancet|language=English|volume=371|issue=9627|pages=1861–1871|doi=10.1016/S0140-6736(08)60800-4|issn=0140-6736|pmid=18514730|s2cid=901857|url-access=subscription}}</ref>

The number of reported cases has been increasing in most countries.<ref name="pmid18761916">{{cite journal |author=Suss J |title=Tick-borne encephalitis in Europe and beyond--the epidemiological situation as of 2007 |journal=Euro Surveill. |volume=13 |issue=26 |date=June 2008 |doi=10.2807/ese.13.26.18916-en |pmid=18761916 |url=http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=18916|doi-access=free }}</ref> TBE is posing a concerning health challenge to Europe, as the number of reported human cases of TBE in all endemic regions of Europe has increased by almost 400% within the last three decades.<ref name="ecdc.europa.eu">{{cite web |title=Factsheet about tick-borne encephalitis (TBE) |url=https://ecdc.europa.eu/en/tick-borne-encephalitis/facts/factsheet |website=European Centre for Disease Prevention and Control |date=18 June 2017 |access-date=15 January 2019}}</ref>

The [[tick-borne encephalitis virus]] is known to infect a range of hosts including [[ruminant]]s, [[bird]]s, [[rodent]]s, carnivores, [[horse]]s, and humans. The disease can also be [[Zoonosis|spread from animals to humans]], with ruminants and dogs providing the principal source of infection for humans.<ref name="WikiVet">[http://en.wikivet.net/Tickborne_Encephalitis_Virus Tickborne Encephalitis Virus] reviewed and published by [[WikiVet]], accessed 12 October 2011.</ref>

==Signs and symptoms==
[[File:TBE symptoms.svg|thumb|220px|Symptoms of TBE-infection]]
The disease is most often [[Biphasic disease|biphasic]]. After an [[incubation period]] of approximately one week (range: 4–28 days) from exposure (tick bite) non-specific symptoms occur. These symptoms are fever, malaise, headache, nausea, vomiting and myalgias that persist for about 5 days.<ref name=":0" /><ref name="ecdc.europa.eu" /><ref name="pmid30678880" /> Then, after approximately one week without symptoms, some of the infected develop neurological symptoms, i.e. meningitis, encephalitis or meningoencephalitis. Myelitis also occurs with or without encephalitis.<ref name=":0" /><ref name="ecdc.europa.eu" /><ref name="pmid30678880">{{cite journal |author=Riccardi N |title=Tick-borne encephalitis in Europe: a brief update on epidemiology, diagnosis, prevention, and treatment. |journal=Eur J Intern Med |volume=62 |pages=1–6 |date=22 January 2019 |pmid=30678880 |doi=10.1016/j.ejim.2019.01.004 |s2cid=59252822 }}</ref><ref name="pmid18755391">{{cite journal |author=Kaiser R |title=Tick-borne encephalitis |journal=Infect. Dis. Clin. North Am. |volume=22 |issue=3 |pages=561–75, x |date=September 2008 |pmid=18755391 |doi=10.1016/j.idc.2008.03.013 }}</ref>

[[Sequela]]e persist for a year or more in approximately one third of people who develop neurological disease. The most common long-term symptoms are headache, concentration difficulties, memory impairment and other symptoms of cognitive dysfunction.<ref name=":0" />

Mortality depends on the subtype of the virus. For the European subtype mortality rates are 0.5% to 2% for people who develop neurological disease.<ref name="ecdc.europa.eu" />

In dogs, the disease also manifests as a neurological disorder with signs varying from [[tremor]]s to [[seizure]]s and death.<ref name="WikiVet"/>

In ruminants, neurological disease is also present, and animals may refuse to eat, appear lethargic, and also develop respiratory signs.<ref name="WikiVet"/>

==Cause==
TBE is caused by [[tick-borne encephalitis virus]], a member of the genus ''[[Flavivirus]]'' in the family [[Flaviviridae]]. It was first isolated in 1937 in the USSR by a team led by [[Lev Zilber|Lev A. Zilber]].
 
Three virus sub-types also exist:
* European or Western tick-borne encephalitis virus (transmitted by ''[[Ixodes ricinus]]'')
* Siberian tick-borne encephalitis virus (transmitted by ''[[Ixodes persulcatus|I. persulcatus]]'')
* Far-Eastern tick-borne encephalitis virus, formerly known as Russian spring summer encephalitis virus (transmitted by ''I. persulcatus'').<ref name="ecdc.europa.eu" /><ref>{{cite web |title=Tick-borne Encephalitis (TBE) |url=https://www.cdc.gov/vhf/tbe/index.html |website=Centers for Disease Control and Prevention |access-date=15 January 2019}}</ref>

The former Soviet Union conducted research on tick-borne diseases, including the TBE viruses.

===Transmission===
[[File:Ixodus ricinus 5x.jpg|thumb|Sheep ticks (''Ixodes ricinus''), such as this engorged female, transmit the disease]]
It is transmitted by the bite of several species of infected [[woodland]] [[tick]]s, including ''Ixodes scapularis'', ''[[Ixodes ricinus|I. ricinus]]'' and ''I. persulcatus'',<ref name="pmid10825054">{{cite journal |vauthors=Dumpis U, Crook D, Oksi J |title=Tick-borne encephalitis |journal=Clin. Infect. Dis. |volume=28 |issue=4 |pages=882–90 |date=April 1999 |pmid=10825054 |doi=10.1086/515195 |doi-access= }}</ref> or (rarely) through the [[pasteurization|non-pasteurized]] milk of infected cows.<ref name="CDC">[http://wwwnc.cdc.gov/travel/yellowbook/2014/chapter-3-infectious-diseases-related-to-travel/tickborne-encephalitis CDC Yellow Book], accessed 5 October 2013.</ref>

=== Milk ===
Infection acquired through [[goat milk]] consumed as raw milk or [[Types of cheese#Fresh and whey cheeses|fresh cheese]] (Frischkäse) has been documented in 2016 and 2017 in the German state of [[Baden-Württemberg]]. None of the infected had neurological disease.<ref name="rki"/>

==Diagnosis==
[[Serology|Detection of specific IgM and IgG antibodies]] in patients' sera combined with typical clinical signs, is the principal method for diagnosis. In more complicated situations, e.g. after vaccination, testing for presence of antibodies in [[cerebrospinal fluid]] may be necessary.<ref name="ecdc.europa.eu" /> It has been stated that [[lumbar puncture]] should always be performed when diagnosing TBE and that [[pleocytosis]] in cerebrospinal fluid should be added to the diagnostic criteria.<ref name=":1">{{Cite journal|last1=Taba|first1=P.|last2=Schmutzhard|first2=E.|last3=Forsberg|first3=P.|last4=Lutsar|first4=I.|last5=Ljøstad|first5=U.|last6=Mygland|first6=Å.|last7=Levchenko|first7=I.|last8=Strle|first8=F.|last9=Steiner|first9=I.|date=October 2017|title=EAN consensus review on prevention, diagnosis and management of tick-borne encephalitis|url=http://doi.wiley.com/10.1111/ene.13356|journal=European Journal of Neurology|language=en|volume=24|issue=10|pages=1214–e61|doi=10.1111/ene.13356|pmid=28762591|s2cid=12844392|url-access=subscription}}</ref>

PCR ([[polymerase chain reaction]]) method is rarely used, since TBE virus RNA is most often not present in patient sera or [[cerebrospinal fluid]] at the time of neurological symptoms.<ref name=":1" />

==Prevention==
[[File:Erkinis encefalitas, Pašušvio miškas.JPG|thumb|left|200px|A sign in a Lithuanian [[forest]], warning about a high probability of being infected by tick-borne encephalitis]]

Prevention includes non-specific (tick-bite prevention) and specific [[prophylaxis]] in the form of a [[vaccination]]. Tick checks, while useful for preventing some other tick-borne diseases such as [[Lyme borreliosis]], would not be expected to be effective in the prevention of tick-borne encephalitis as the virus is transmitted within minutes of attachment by the tick.<ref>{{cite journal|doi=10.12998/wjcc.v3.i5.430|title=Tick-borne encephalitis: A review of epidemiology, clinical characteristics, and management |year=2015 |last1=Bogovic |first1=Petra |last2=Strle |first2=F. |journal=World Journal of Clinical Cases |volume=3 |issue=5 |pages=430–441 |pmid=25984517 |pmc=4419106 |doi-access=free }}</ref>

[[Tick-borne encephalitis vaccine]]s are very effective and available in many disease endemic areas and in travel clinics.<ref>{{cite journal |vauthors=Demicheli V, Debalini MG, Rivetti A |title=Vaccines for preventing tick-borne encephalitis |journal=Cochrane Database Syst Rev |issue=1 |pages=CD000977 |year=2009 |volume=2009 |doi=10.1002/14651858.CD000977.pub2 |pmid=19160184 |pmc=6532705 |editor1-last=Demicheli |editor1-first=Vittorio}}</ref> Trade names are ''Encepur N''<ref>{{Cite web|url=https://compendium.ch/mpro/mnr/27219/html/de|title=Encepur® N|website=compendium.ch|access-date=21 January 2018|date=28 April 2016}}</ref> and ''FSME-Immun CC''.<ref>{{Cite web|url=https://compendium.ch/mpro/mnr/26452/html/de|title=FSME-Immun® CC|website=compendium.ch|access-date=21 January 2018|date=11 August 2017}}</ref>

==Treatment==
There is no specific [[antiviral]] treatment for TBE. Symptomatic brain damage requires hospitalization and [[supportive care]] based on [[syndrome]] severity. [[Anti-inflammatory drugs]], such as [[corticosteroid]]s, may be considered under specific circumstances for symptomatic relief. [[Tracheal intubation]] and [[Respiratory physiology|respiratory]] support may be necessary.

==Epidemiology==
As of 2011, the disease was most common in Central and Eastern Europe, and Northern Asia.<!-- <ref name=WHO2011/> --> About ten to twelve thousand cases are documented a year but the rates vary widely from one region to another.<ref name=WHO2011>{{cite journal|title=Vaccines against tick-borne encephalitis: WHO position paper |journal=Weekly Epidemiological Record |date=June 2011|volume=86|issue=24|pages=241–256|pmid=21661276 | hdl=10665/241769 | hdl-access=free }}</ref> Most of the variation has been the result of variation in host population, particularly that of deer. In Austria, an extensive vaccination program since the 1970s reduced the incidence in 2013 by roughly 85%.<ref name="Amicizia 1163–1171">{{Cite journal|last1=Amicizia|first1=Daniela|last2=Domnich|first2=Alexander|last3=Panatto|first3=Donatella|last4=Lai|first4=Piero Luigi|last5=Cristina|first5=Maria Luisa|last6=Avio|first6=Ulderico|last7=Gasparini|first7=Roberto|date=14 May 2013|title=Epidemiology of tick-borne encephalitis (TBE) in Europe and its prevention by available vaccines|journal=Human Vaccines & Immunotherapeutics|volume=9|issue=5|pages=1163–1171|doi=10.4161/hv.23802|issn=2164-5515|pmc=3899155|pmid=23377671}}</ref>

In Germany, during the 2010s, there have been a minimum of 95 (2012) and a maximum of 584 cases (2018) of TBE  (or FSME as it is known in German). More than half of the reported cases from 2019 had [[meningitis]], [[encephalitis]] or [[myelitis]]. The risk of infection was noted to be increasing with age, especially in people older than 40 years and it was greater in men than women. Most cases were acquired in Bavaria (46%) and Baden-Württemberg (37%), much less in Saxony, Hesse, Lower Saxony and other states. Altogether 164 [[Landkreis]]e are designated TBE-risk areas, including all of Baden-Württemberg except for the city of Heilbronn.<ref name="rki">{{Cite journal |year=2020 |title=FSME: Risikogebiete in Deutschland  |url=https://www.rki.de/DE/Content/Infekt/EpidBull/Archiv/2020/Ausgaben/08_20.pdf |journal=Epidemiologisches Bulletin, RKI |language=de |location=Berlin |volume=8}}</ref>

In Sweden, most cases of TBE occur in a band running from Stockholm to the west, especially around lakes and the nearby region of the Baltic sea.<ref>{{Cite journal|last1=Pettersson|first1=John H.-O.|last2=Golovljova|first2=Irina|last3=Vene|first3=Sirkka|last4=Jaenson|first4=Thomas G. T.|date=1 January 2014|title=Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern Sweden|journal=Parasites & Vectors|volume=7|pages=102|doi=10.1186/1756-3305-7-102|issn=1756-3305|pmc=4007564|pmid=24618209 |doi-access=free }}</ref><ref>{{Cite journal|title=Tick-borne encephalitis increasing in Sweden, 2011|journal=Eurosurveillance|volume=16 |issue=39 |language=en|doi=10.2807/ese.16.39.19981-en|pmid=21968422|year=2011|doi-access=free |last1=Lundkvist |first1=Å. |last2=Wallensten |first2=A. |last3=Vene |first3=S. |last4=Hjertqvist |first4=M. }}</ref> It reflects the greater population involved in [[outdoor activities]] in these areas. Overall, for Europe, the estimated risk is roughly 1 case per 10,000 human-months of [[woodland]] activity. Although in some regions of Russia and Slovenia, the prevalence of cases can be as high as 70 cases per 100,000 people per year.<ref name="Amicizia 1163–1171"/><ref>{{Cite journal|url=http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20003|title=Case report: Tick-borne encephalitis in two Dutch travellers returning from Austria, Netherlands, July and August 2011|journal=Eurosurveillance|volume=16|issue=44|pages=20003|last=team|first=European Centre for Disease Prevention and Control (ECDC)-Health Communication Unit- Eurosurveillance editorial|date=11 March 2011|language=en|access-date=4 June 2016|doi=10.2807/ese.16.44.20003-en|pmid=22085619|doi-access=free}}</ref> Travelers to endemic regions do not often become cases, with only 8 cases reported among U.S. travelers returning from Eurasia between 2000 and 2017, a rate so low that as of 2020 the U.S. [[Centers for Disease Control and Prevention]] recommended vaccination only for those who will be extensively exposed in high risk areas.<ref>{{Cite web|url=https://wwwnc.cdc.gov/travel/yellowbook/2020/travel-related-infectious-diseases/tickborne-encephalitis |title=Tickborne Encephalitis |work=CDC.gov |access-date=4 June 2016}}</ref>
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==References==
{{Reflist}}

== External links ==
{{Medical resources
|  DiseasesDB     = 29274
|  ICD11          = {{ICD11|1C8G}}
|  ICD10          = {{ICD10|A|84||a|80}}
|  ICD9           = {{ICD9|063}}
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|  MeshID         = D004675
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* [https://wwwnc.cdc.gov/travel/yellowbook/2018/infectious-diseases-related-to-travel/tickborne-encephalitis Tickborne encephalitis] at [[Centers for Disease Control and Prevention]] (CDC)
* [https://www.cdc.gov/vhf/tbe/resources/index.html Factsheet] from Viral Special Pathogens Branch at the CDC
{{Viral diseases}}
{{Zoonotic viral diseases}}
{{Tick-borne diseases}}

{{Authority control}}

{{DEFAULTSORT:Tick-Borne Encephalitis}}
[[Category:Tick-borne diseases]]
[[Category:Viral encephalitis]]
[[Category:Slow virus diseases]]
[[Category:Vaccine-preventable diseases]]
[[Category:Zoonoses]]