Powassan virus

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Powassan virus
Systematics
Classification : Viruses
Area : Riboviria
Empire : Orthornavirae
Phylum : Kitrinoviricota
Class : Flasuviricetes
Order : Amarillovirales
Family : Flaviviridae
Genre : Flavivirus
Type : Powassan virus
Taxonomic characteristics
Genome : (+) ssRNA linear
Baltimore : Group 4
Symmetry : icosahedral
Cover : available
Scientific name
Powassan Virus
Short name
POWV
Left
NCBI  Taxonomy: 11083
ICTV Taxon History: 201853104

The Powassan virus is a species of the genus Flavivirus , which of ticks is transmitted. It occurs in North America and eastern Siberia . The name is derived from the city of Powassan in Ontario . There the virus was first discovered in a little boy who died from it. The Powassan virus , an encephalitis cause. So far there is no vaccination and no effective drug therapy against the virus. Avoiding tick bites in endemic areas is the best precaution.

Occurrence

The virus is mainly found in North America. It is the only flavivirus in North America that is transmitted by ticks and is pathogenic in humans. Furthermore, the Powassan virus found in the warmer zones Eurasiens, where part of the tick-borne encephalitis virus complex ( Tick-Borne Encephalitis complex is TBE). It occurs in the southeast of Siberia in Primorsky Krai and was probably introduced there 70 years ago.

evolution

The Powassan virus is an RNA virus that is split into 2 separate lineages:

  • Line 1 is also called the prototype line,
  • Line 2 the deer tick virus line (DTV, Deer-Tick-Virus).

Line 2 has the greater genetic variability. This is an indication that it is the older lineage that was split by natural selection. The deer tick virus line is very similar to the Powassan virus prototype. A sequence analysis showed an agreement of the nucleic acid sequence in 84% and the amino acid sequence in 94%. According to this, the two lines must have separated about 200 years ago. Although line 2 dominates in Powassan virus positive tick populations, disease in both lines has been detected in both North America and Siberia. Since the coat protein of flaviviruses is highly conserved, there are often immunological cross-reactions of different types. This makes the immunological differentiation of these flaviviruses extremely difficult. They are considered to be serologically indistinguishable. Therefore, both virus lines are assigned to the same species.

transmission

The Powassan virus can be transmitted when the following tick species of the genera Ixodes and Dermacentor are bitten :

The Ixodes cookei bite is relatively rare. Usually a deer tick virus is transmitted. Ixodes scapularis is an important vector of the deer tick virus and plays an important role in the Powassan virus . Also for the transmission of Lyme disease is Ixodes scapularis significant because it affects different species of mammals and biting people instantly. In Canada and the northeastern part of the United States, Ixodes cookei is the predominant tick species, in Minnesota and Wisconsin, however, Ixodes scapularis . In North America, Powassan virus is transmitted to humans by three different types of mammals through three different types of ticks. Ixodes cookei transmits Powassan virus from marmots to humans, Ixodes marxi from squirrels, and Ixodes scapularis from North American whitefooted mice.

Based on knowledge of other pathogens transmitted by ticks, such as Lyme disease or anaplasmosis , it is believed that a tick can infect humans less than 12 hours after ingesting the Powassan virus . The Powassan virus was not transmitted back from humans to other mammals by ticks. Infections in humans are a dead end for the Powassan virus .

Clinical picture

Powassan virus infection is rarely the cause of encephalitis. Powassan virus encephalitis is usually severe and permanent neurological changes are common. Powassan virus encephalitis symptoms are similar to acute disseminated encephalomyelitis. The diagnosis is made even more difficult by the fact that only a few laboratories are able to carry out serological Powassan virus testing. A direct virus detection in the blood or liquor by PCR or culture is unfortunately only possible in the prodromal phase . The first symptoms appear one to three weeks after infection. The illness begins with fever, headache, nausea, occasional confusion and general weakness. Because of the severity of the disease, inpatient treatment is recommended. As the disease progresses, the typical symptoms of meningoencephalitis appear: cramps , language disorders , cranial nerve paralysis , paresis and impaired consciousness . Since there is currently no vaccination and no effective specific drug therapy, treatment must be symptomatic. This consists of combating brain swelling, intravenous fluid treatment and, if necessary, ventilation. About 10% of Powassan virus encephalitis cases die; of those who survive, about 50% have permanent neurological changes. Between 2000 and 2011, 49 patients died in the United States from Powassan virus encephalitis.

In 2017, the rare case of infection in a 5 month old Connecticut boy was published. He survived the disease with normal motor and language development at 10 months of age. The MRI showed severe brain changes such as gliosis and encephalomalacia of the thalamus and basal ganglia on both sides, a loss of volume and calcification of the left basal ganglia.

prevention

Prevention is particularly important for diseases that are transmitted by ticks. The risk of a tick bite is particularly high in dense forest areas and areas with tall grass. It is recommended to wear loose clothing that covers all areas of the skin. This includes long pants and high socks. This prevents ticks from directly attacking human skin. After being outdoors, you should carefully check your own body for ticks. It is also helpful to have friends or family members scan each other's skin. There is also the option of treating clothing with tick-repellent agents, for example with preparations containing permethrin . There are also repellent products to protect pets against tick bites. Pets that have been in such areas must also be carefully checked for ticks.

In addition, it must be remembered that the first signs only appear after 7–21 days. If neurological symptoms occur during this period, the attending physician should be informed that a tick bite has occurred.

Individual evidence

  1. ↑ ICTV Master Species List 2018b.v2 . MSL # 34, March 2019
  2. ↑ a b c d e ICTV: ICTV Taxonomy history: Yellow fever virus , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
  3. ↑ a b c d e Mark D. Hicar, Kathryn Edwards, Karen Bloch: Powassan virus infection presenting as acute disseminated encephalomyelitis in Tennessee . In: The Pediatric Infectious Disease Journal . tape 30 , no. 1 , 2011, ISSN  1532-0987 , p. 86-88 , doi : 10.1097 / INF.0b013e3181f2f492 , PMID 20736878 .
  4. ^ A b c d e Justin Birge, Steven Sonnesyn: Powassan virus encephalitis, Minnesota, USA . In: Emerging Infectious Diseases . tape 18 , no. October 10 , 2012, ISSN  1080-6059 , p. 1669–1671 , doi : 10.3201 / eid1810.120621 , PMID 23017222 , PMC 3471639 (free full text).
  5. ↑ Gerhard Dobler: Zoonotic tick-borne flaviviruses . In: Veterinary Microbiology . tape 140 , no. 3-4 , January 27, 2010, ISSN  1873-2542 , p. 221-228 , doi : 10.1016 / j.vetmic.2009.08.024 , PMID 19765917 .
  6. ^ NCBI: tick-borne encephalitis virus group
  7. ↑ a b c d e f g Doug E. Brackney, Ivy K. Brown, Robert A. Nofchissey, Kelly A. Fitzpatrick, Gregory D. Ebel: Homogeneity of Powassan virus populations in naturally infected Ixodes scapularis . In: Virology . tape 402 , no. 2 , July 5, 2010, ISSN  1096-0341 , p. 366–371 , doi : 10.1016 / j.virol.2010.03.035 , PMID 20434750 , PMC 2875267 (free full text).
  8. ↑ EL Subbotina, VB Loktev: [Molecular evolution of the tick-borne encephalitis and Powassan viruses] . In: Moleculiarnaia Biologiia . tape 46 , no. 1 , 2012, ISSN  0026-8984 , p. 82-92 , PMID 22642104 .
  9. ↑ NCBI: Tick-borne powassan virus (strain lb)
  10. ^ NCBI: Deer tick virus
  11. ↑ Kendra N. Pesko, Fernando Torres-Perez, Brian L. Hjelle, Gregory D. Ebel: Molecular epidemiology of Powassan virus in North America . In: The Journal of General Virology . tape 91 , Pt 11, November 2010, ISSN  1465-2099 , p. 2698-2705 , doi : 10.1099 / vir.0.024232-0 , PMID 20631087 , PMC 3052558 (free full text).
  12. ↑ a b c d e f Centers for Disease Control and Prevention. (2010). Powassan. Retrieved from https://www.cdc.gov/powassan/
  13. ^ A b Justin Birge, Steven Sonnesyn: Powassan virus encephalitis, Minnesota, USA . In: Emerging Infectious Diseases . tape 18 , no. 10 , 2012, ISSN  1080-6059 , p. 1669–1671 , doi : 10.3201 / eid1810.120621 , PMID 23017222 , PMC 3471639 (free full text).
  14. ↑ a b Minnesota Department of Health . In: Powassan . MDH. Retrieved October 27, 2013.
  15. ↑ David F. Neitzel, Ruth Lynfield, Kirk Smith: Powassan virus encephalitis, Minnesota, USA . In: Emerging Infectious Diseases . tape 19 , no. 4 , 2013, ISSN  1080-6059 , p. 686 , doi : 10.3201 / eid1904.121651 , PMID 23750562 , PMC 3647426 (free full text).
  16. ↑ Meghan E Hermance, Saravanan Thangamani: Powassan Virus: An Emerging Arbovirus of Public Health Concern in North America . In: Vector Borne and Zoonotic Diseases (Larchmont, NY) . tape 17 , no. 7 , 2017, ISSN  1557-7759 , p. 453-462 , doi : 10.1089 / vbz.2017.2110 , PMID 28498740 , PMC 5512300 (free full text).
  17. ↑ Jessica W. Tutolo, J. Erin Staples, Lynn Sosa, Nicholas Bennett: Notes from the Field: Powassan Virus Disease in an Infant - Connecticut, 2016 . In: MMWR. Morbidity and Mortality Weekly Report . tape 66 , no. 15 , April 21, 2017, ISSN  0149-2195 , p. 408-409 , doi : 10.15585 / mmwr.mm6615a3 , PMID 28426641 , PMC 5687186 (free full text).
  18. Jump up ↑ Diep K Hoang Johnson, J Erin Staples, Mark J Sotir, David M Warshauer, Jeffrey P Davis: Tickborne Powassan virus infections among Wisconsin residents . In: WMJ: official publication of the State Medical Society of Wisconsin . tape 109 , no. 2 , 2010, ISSN  1098-1861 , p. 91-97 , PMID 20443328 .
  19. ^ National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Division of Vector-Borne Diseases (DVBD): Preventing Ticks on Your Pets. Centers for Disease Control and Prevention (CDC), accessed March 3, 2019 .