Tick-borne encephalitis

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Tick-borne meningoencephalitis
EurAsia TBE-belt.svg
Infected countries/areas in Eurasia
Specialty Infectious disease

Tick-borne encephalitis (TBE) is a viral infectious disease involving the central nervous system. The disease most often manifests as meningitis, encephalitis or meningoencephalitis. Myelitis and spinal paralysis also occurs. In about one third of cases sequelae, predominantly cognitive dysfunction, persist for a year or more. [1]

Contents

The number of reported cases has been increasing in most countries. [2] TBE is posing a concerning health challenge to Europe, as the number of reported human cases of TBE in all endemic regions of Europe have increased by almost 400% within the last three decades. [3]

The tick-borne encephalitis virus is known to infect a range of hosts including ruminants, birds, rodents, carnivores, horses, and humans. The disease can also be spread from animals to humans, with ruminants and dogs providing the principal source of infection for humans. [4]

Signs and symptoms

Symptoms of TBE-infection TBE symptoms.svg
Symptoms of TBE-infection

The disease is most often biphasic. After an incubation period of approximately one week (range: 4–28 days) from exposure (tick bite) non-specific symptoms occurs. These symptoms are fever, malaise, headache, nausea, vomiting and myalgias that persist for about 5 days. [1] [3] [5] 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. [1] [3] [5] [6]

Sequelae persist for a year or more in approximately one third of people who develop neurological disease. Most common long-term symptoms are headache, concentration difficulties, memory impairment and other symptoms of cognitive dysfunction. [1]

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. [3]

In dogs, the disease also manifests as a neurological disorder with signs varying from tremors to seizures and death. [4]

In ruminants, neurological disease is also present, and animals may refuse to eat, appear lethargic, and also develop respiratory signs. [4]

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. Three virus sub-types also exist:

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

Transmission

Sheep ticks (Ixodes ricinus), such as this engorged female, transmit the disease Ixodus ricinus 5x.jpg
Sheep ticks (Ixodes ricinus), such as this engorged female, transmit the disease

It is transmitted by the bite of several species of infected woodland ticks, including Ixodes scapularis, I. ricinus and I. persulcatus, [8] or (rarely) through the non-pasteurized milk of infected cows. [9]

Milk

Infection acquired through goat milk consumed as raw milk or fresh cheese (Frischkäse) has been documented in 2016 and 2017 in the German state of Baden-Württemberg. None of the infected had neurological disease. [10]

Diagnosis

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. [3] It has been stated that lumbar puncture always should be performed when diagnosing TBE and that pleocytosis in cerebrospinal fluid should be added to the diagnostic criteria. [11]

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. [11]

Prevention

A sign in a Lithuanian forest, warning about a high probability of being infected by tick-borne encephalitis Erkinis encefalitas, Pasusvio miskas.JPG
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. [12]

Tick-borne encephalitis vaccines are very effective and available in many disease endemic areas and in travel clinics. [13] Trade names are Encepur N [14] and FSME-Immun CC. [15]

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 corticosteroids, may be considered under specific circumstances for symptomatic relief. Tracheal intubation and respiratory support may be necessary.

Epidemiology

As of 2011, the disease was most common in Central and Eastern Europe, and Northern Asia. About ten to twelve thousand cases are documented a year but the rates vary widely from one region to another. [16] 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%. [17]

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 Landkreise are designated TBE-risk areas, including all of Baden-Württemberg except for the city of Heilbronn. [10]

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. [18] [19] 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. [17] [20] 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. [21]

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<span class="mw-page-title-main">Lyme disease</span> Infectious disease caused by Borrelia bacteria, spread by ticks

Lyme disease, also known as Lyme borreliosis, is a tick-borne disease caused by species of Borrelia bacteria, transmitted by blood-feeding ticks in the genus Ixodes. The most common sign of infection is an expanding red rash, known as erythema migrans (EM), which appears at the site of the tick bite about a week afterwards. The rash is typically neither itchy nor painful. Approximately 70–80% of infected people develop a rash. Early diagnosis can be difficult. Other early symptoms may include fever, headaches and tiredness. If untreated, symptoms may include loss of the ability to move one or both sides of the face, joint pains, severe headaches with neck stiffness or heart palpitations. Months to years later, repeated episodes of joint pain and swelling may occur. Occasionally, shooting pains or tingling in the arms and legs may develop. Despite appropriate treatment, about 10 to 20% of those affected develop joint pains, memory problems, and tiredness for six months or more; this constellation of symptoms is termed post-treatment Lyme disease syndrome (PTLDS).

<span class="mw-page-title-main">Arbovirus</span> Class of viruses which are transmitted by arthropods

Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term arbovirus is a portmanteau word. Tibovirus is sometimes used to more specifically describe viruses transmitted by ticks, a superorder within the arthropods. Arboviruses can affect both animals and plants. In humans, symptoms of arbovirus infection generally occur 3–15 days after exposure to the virus and last three or four days. The most common clinical features of infection are fever, headache, and malaise, but encephalitis and viral hemorrhagic fever may also occur.

Tick-borne diseases, which afflict humans and other animals, are caused by infectious agents transmitted by tick bites. They are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and protozoa. The economic impact of tick-borne diseases is considered to be substantial in humans, and tick-borne diseases are estimated to affect ~80 % of cattle worldwide. Most of these pathogens require passage through vertebrate hosts as part of their life cycle. Tick-borne infections in humans, farm animals, and companion animals are primarily associated with wildlife animal reservoirs. Many tick-borne infections in humans involve a complex cycle between wildlife animal reservoirs and tick vectors. The survival and transmission of these tick-borne viruses are closely linked to their interactions with tick vectors and host cells. These viruses are classified into different families, including Asfarviridae, Reoviridae, Rhabdoviridae, Orthomyxoviridae, Bunyaviridae, and Flaviviridae.

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<i>Tick-borne encephalitis virus</i> Species of virus

Tick-borne encephalitis virus (TBEV) is a positive-strand RNA virus associated with tick-borne encephalitis in the genus Flavivirus.

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References

  1. 1 2 3 4 Lindquist, Lars; Vapalahti, Olli (31 May 2008). "Tick-borne encephalitis". The Lancet. 371 (9627): 1861–1871. doi:10.1016/S0140-6736(08)60800-4. ISSN   0140-6736. PMID   18514730. S2CID   901857.
  2. ↑ Suss J (June 2008). "Tick-borne encephalitis in Europe and beyond--the epidemiological situation as of 2007". Euro Surveill. 13 (26). doi: 10.2807/ese.13.26.18916-en . PMID   18761916.
  3. 1 2 3 4 5 6 "Factsheet about tick-borne encephalitis (TBE)". European Centre for Disease Prevention and Control. 18 June 2017. Retrieved 15 January 2019.
  4. 1 2 3 Tickborne Encephalitis Virus reviewed and published by WikiVet, accessed 12 October 2011.
  5. 1 2 Riccardi N (22 January 2019). "Tick-borne encephalitis in Europe: a brief update on epidemiology, diagnosis, prevention, and treatment". Eur J Intern Med. 62: 1–6. doi:10.1016/j.ejim.2019.01.004. PMID   30678880. S2CID   59252822.
  6. ↑ Kaiser R (September 2008). "Tick-borne encephalitis". Infect. Dis. Clin. North Am. 22 (3): 561–75, x. doi:10.1016/j.idc.2008.03.013. PMID   18755391.
  7. ↑ "Tick-borne Encephalitis (TBE)". Centers for Disease Control and Prevention. Retrieved 15 January 2019.
  8. ↑ Dumpis U, Crook D, Oksi J (April 1999). "Tick-borne encephalitis". Clin. Infect. Dis. 28 (4): 882–90. doi:10.1086/515195. PMID   10825054.
  9. ↑ CDC Yellow Book, accessed 5 October 2013.
  10. 1 2 "FSME: Risikogebiete in Deutschland" (PDF). Epidemiologisches Bulletin, RKI (in German). 8. Berlin. 2020.
  11. 1 2 Taba, P.; Schmutzhard, E.; Forsberg, P.; Lutsar, I.; Ljøstad, U.; Mygland, Å.; Levchenko, I.; Strle, F.; Steiner, I. (October 2017). "EAN consensus review on prevention, diagnosis and management of tick-borne encephalitis". European Journal of Neurology. 24 (10): 1214–e61. doi:10.1111/ene.13356. PMID   28762591. S2CID   12844392.
  12. ↑ Bogovic, Petra; Strle, F. (2015). "Tick-borne encephalitis: A review of epidemiology, clinical characteristics, and management". World Journal of Clinical Cases. 3 (5): 430–441. doi: 10.12998/wjcc.v3.i5.430 . PMC   4419106 . PMID   25984517.
  13. ↑ Demicheli V, Debalini MG, Rivetti A (2009). Demicheli V (ed.). "Vaccines for preventing tick-borne encephalitis". Cochrane Database Syst Rev. 2009 (1): CD000977. doi:10.1002/14651858.CD000977.pub2. PMC   6532705 . PMID   19160184.
  14. ↑ "Encepur® N". compendium.ch. 28 April 2016. Retrieved 21 January 2018.
  15. ↑ "FSME-Immun® CC". compendium.ch. 11 August 2017. Retrieved 21 January 2018.
  16. ↑ "Vaccines against tick-borne encephalitis: WHO position paper". Weekly Epidemiological Record. 86 (24): 241–256. June 2011. hdl: 10665/241769 . PMID   21661276.
  17. 1 2 Amicizia, Daniela; Domnich, Alexander; Panatto, Donatella; Lai, Piero Luigi; Cristina, Maria Luisa; Avio, Ulderico; Gasparini, Roberto (14 May 2013). "Epidemiology of tick-borne encephalitis (TBE) in Europe and its prevention by available vaccines". Human Vaccines & Immunotherapeutics. 9 (5): 1163–1171. doi:10.4161/hv.23802. ISSN   2164-5515. PMC   3899155 . PMID   23377671.
  18. ↑ Pettersson, John H.-O.; Golovljova, Irina; Vene, Sirkka; Jaenson, Thomas G. T. (1 January 2014). "Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern Sweden". Parasites & Vectors. 7: 102. doi: 10.1186/1756-3305-7-102 . ISSN   1756-3305. PMC   4007564 . PMID   24618209.
  19. ↑ Lundkvist, Å.; Wallensten, A.; Vene, S.; Hjertqvist, M. (2011). "Tick-borne encephalitis increasing in Sweden, 2011". Eurosurveillance. 16 (39). doi: 10.2807/ese.16.39.19981-en . PMID   21968422.
  20. ↑ team, European Centre for Disease Prevention and Control (ECDC)-Health Communication Unit- Eurosurveillance editorial (11 March 2011). "Case report: Tick-borne encephalitis in two Dutch travellers returning from Austria, Netherlands, July and August 2011". Eurosurveillance. 16 (44): 20003. doi: 10.2807/ese.16.44.20003-en . PMID   22085619 . Retrieved 4 June 2016.
  21. ↑ "Tickborne Encephalitis". CDC.gov. Retrieved 4 June 2016.
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