Usutu virus

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Usutu virus
Usutu Virus model, its gene structure, and the proteins encoded by its genome - Viruses-07-00219-g002.png
Virus classification OOjs UI icon edit-ltr.svg
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Kitrinoviricota
Class: Flasuviricetes
Order: Amarillovirales
Family: Flaviviridae
Genus: Flavivirus
Species:
Usutu virus

Usutu virus (USUV) is a flavivirus belonging to the Japanese encephalitis complex, which is an emerging zoonotic arbovirus of concern because of its pathogenicity to humans and its similarity in ecology with other emerging arboviruses such as West Nile virus. [1] It mainly infects Culex mosquitoes and birds; humans form a dead-end host. First identified in South Africa in 1959, the virus has caused outbreaks in birds across Europe since 1996. Nearly 50 cases in humans have been reported as of 2019, mainly in Europe. These are predominantly asymptomatic, but some people experience neurological symptoms.

Contents

History

USUV was first identified by Bruce McIntosh in Culex neavei mosquitoes in South Africa in 1959, [2] [3] and is named after the Usutu River. [4] [5] The virus was later identified in Mansonia aurites mosquitoes in Uganda. [3] In 1996, USUV was identified outside Africa for the first time, causing significant mortality among Old World blackbirds in Italy. [6]

Only two human cases have been identified in Africa, in 1981 and 2004, with one benign and one severe case described. [1] The first human case outside Africa was reported in Italy in 2009, where an immunocompromised patient was infected, causing encephalitis. [7]

Immunohistochemistry (IHC) of USUV-uninfected (A, C) and -infected (B, D, F and F) blackbird organs using an USUV-specific murine monoclonal antibody.
(A) USUV-uninfected blackbird brain.
(B) USUV-infected blackbird brain showing a group of USUV-positive neurons (in red).
(C) USUV-uninfected blackbird heart.
(D) USUV-infected blackbird heart, USUV-positive cells are localized in the endocardium (in red).
(E) USUV-infected blackbird liver, disseminated USUV-positive Kupffer cells (in red).
(F) USUV-infected blackbird lung, disseminated USUV-positive cells (in red). Usutu Immunohistochemistry (IHC) of USUVuninfected (A, C) and infected (B, D, F and F) blackbird organs PlosOne.png
Immunohistochemistry (IHC) of USUV-uninfected (A, C) and –infected (B, D, F and F) blackbird organs using an USUV-specific murine monoclonal antibody.
(A) USUV-uninfected blackbird brain.
(B) USUV-infected blackbird brain showing a group of USUV-positive neurons (in red).
(C) USUV-uninfected blackbird heart.
(D) USUV-infected blackbird heart, USUV-positive cells are localized in the endocardium (in red).
(E) USUV-infected blackbird liver, disseminated USUV-positive Kupffer cells (in red).
(F) USUV-infected blackbird lung, disseminated USUV-positive cells (in red).

Virology

USUV has a diameter of 40–60 nm and is enveloped. The genome is a +-sense, single-stranded RNA of 11,064 nucleotides with a 5′ N7-methylguanosine-triphosphate cap. There is one open reading frame, which encodes a 3434-amino acid polyprotein. This is processed to generate eleven proteins: three structural and eight non-structural proteins. Replication occurs in the cytoplasm of the host cell. [3] The virus has eight lineages, five in Europe and three in Africa. [3]

Epidemiology and host range

USUV has been reported from several African countries including Burkina Faso, Central African Republic, Côte d'Ivoire, Morocco, Nigeria, Senegal, South Africa, Tunisia and Uganda, [1] [3] as well as from Israel. Since 1996, it has also been found in European countries, including Austria, Belgium, Croatia, Czech Republic, France, Germany, Greece, Hungary, Italy, Serbia, Spain and Switzerland, and more recently the Netherlands, and was spreading across Europe in the late 2010s. Outbreaks are often simultaneous with those of the related West Nile virus . [3]

USUV's host range includes primarily Culex mosquitoes and birds. [1] The main bird hosts are blackbirds (Turdus merula), magpies (Pica pica) and owls, including the great grey owl (Strix nebulosa). In addition to humans, the virus has been isolated from Pipistrellus bats, and anti-USUV antibodies have been found in horses, dogs, deer, wild boar, rodents and shrews. Humans and horses are dead-end hosts. [3] The vector is one of several mosquitoes that bite birds, in Europe particularly Culex pipiens . [3] For example, a 2008–2009 survey of mosquitoes and birds in the Emilia-Romagna region of Italy detected USUV in 89 C. pipiens pools and in 2 Aedes albopictus pools, suggesting the possible involvement of A. albopictus in the virus cycle. The virus was also found in twelve wild birds, primarily Eurasian magpies (P. pica), hooded crows (Corvus cornix), and Eurasian jays (Garrulus glandarius). [8] In Africa multiple Culex species are involved, as well as several species of Aedes and other mosquitoes. [3]

In 2020 the virus was detected in London, and has spread in wild birds since. [9]

Disease

Two cases of symptomatic infection in humans have been reported from Africa, with fever and skin rash but no neurological symptoms. In Europe, 46 infections were detected up to 2019; these were mainly asymptomatic, but neurological symptoms including encephalitis and meningoencephalitis have been observed. [3]

The virus is highly pathogenic in birds, causing central nervous system symptoms, enlargement of the liver and spleen, and infiltration by inflammatory cells in a wide range of organs. [3]

Related Research Articles

<span class="mw-page-title-main">West Nile fever</span> Human disease caused by West Nile virus infection

West Nile fever is an infection by the West Nile virus, which is typically spread by mosquitoes. In about 80% of infections people have few or no symptoms. About 20% of people develop a fever, headache, vomiting, or a rash. In less than 1% of people, encephalitis or meningitis occurs, with associated neck stiffness, confusion, or seizures. Recovery may take weeks to months. The risk of death among those in whom the nervous system is affected is about 10 percent.

<i>Aedes albopictus</i> Species of mosquito

Aedes albopictus, from the mosquito (Culicidae) family, also known as the (Asian) tiger mosquito or forest mosquito, is a mosquito native to the tropical and subtropical areas of Southeast Asia. In the past few centuries, however, this species has spread to many countries through the transport of goods and international travel. It is characterized by the white bands on its legs and body.

<i>Flavivirus</i> Genus of viruses

Flavivirus, renamed Orthoflavivirus in 2023, is a genus of positive-strand RNA viruses in the family Flaviviridae. The genus includes the West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, Zika virus and several other viruses which may cause encephalitis, as well as insect-specific flaviviruses (ISFs) such as cell fusing agent virus (CFAV), Palm Creek virus (PCV), and Parramatta River virus (PaRV). While dual-host flaviviruses can infect vertebrates as well as arthropods, insect-specific flaviviruses are restricted to their competent arthropods. The means by which flaviviruses establish persistent infection in their competent vectors and cause disease in humans depends upon several virus-host interactions, including the intricate interplay between flavivirus-encoded immune antagonists and the host antiviral innate immune effector molecules.

<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.

La Crosse encephalitis is an encephalitis caused by an arbovirus which has a mosquito vector.

Murray Valley encephalitis virus (MVEV) is a zoonotic flavivirus endemic to northern Australia and Papua New Guinea. It is the causal agent of Murray Valley encephalitis. In humans, it can cause permanent neurological disease or death. MVEV is related to Kunjin virus, which has a similar ecology, but a lower morbidity rate. Although the arbovirus is endemic to Northern Australia, it has occasionally spread to the southern states during times of heavy rainfall during the summer monsoon season via seasonal flooding of the Murray-Darling River system. These outbreaks can be "...decades apart, with no or very few cases identified in between".

<span class="mw-page-title-main">Viral encephalitis</span> Medical condition

Viral encephalitis is inflammation of the brain parenchyma, called encephalitis, by a virus. The different forms of viral encephalitis are called viral encephalitides. It is the most common type of encephalitis and often occurs with viral meningitis. Encephalitic viruses first cause infection and replicate outside of the central nervous system (CNS), most reaching the CNS through the circulatory system and a minority from nerve endings toward the CNS. Once in the brain, the virus and the host's inflammatory response disrupt neural function, leading to illness and complications, many of which frequently are neurological in nature, such as impaired motor skills and altered behavior.

<i>Culex</i> Genus of mosquitoes

Culex or typical mosquitoes are a genus of mosquitoes, several species of which serve as vectors of one or more important diseases of birds, humans, and other animals. The diseases they vector include arbovirus infections such as West Nile virus, Japanese encephalitis, or St. Louis encephalitis, but also filariasis and avian malaria. They occur worldwide except for the extreme northern parts of the temperate zone, and are the most common form of mosquito encountered in some major U.S. cities, such as Los Angeles.

<span class="mw-page-title-main">London Underground mosquito</span> Species of fly

The London Underground mosquito is a form of mosquito in the genus Culex. It is found in the London Underground railway system as its name suggests, but has a worldwide distribution and long predates the existence of the London Underground. It was first described as a distinct species from Egyptian specimens by the biologist Peter Forsskål (1732–1763). He named this mosquito Culex molestus due to its voracious biting, but later biologists renamed it Culex pipiens f. molestus because there were no morphological differences between it and Culex pipiens. Notably, this mosquito assaulted Londoners sleeping in the Underground during the Blitz, although similar populations were long known.

<i>Culex pipiens</i> Species of fly

Culex pipiens is a species of mosquito commonly referred to as the common house mosquito or northern house mosquito, as it is the most common mosquito to the northern regions of the US. They can be found in both urban and suburban temperate and tropical regions across the world.

<span class="mw-page-title-main">Mosquito-borne disease</span> Diseases caused by bacteria, viruses or parasites transmitted by mosquitoes

Mosquito-borne diseases or mosquito-borne illnesses are diseases caused by bacteria, viruses or parasites transmitted by mosquitoes. Nearly 700 million people contract mosquito-borne illnesses each year, resulting in more than a million deaths.

Rocio viral encephalitis is an epidemic flaviviral disease of humans first observed in São Paulo State, Brazil, in 1975. Low-level enzootic transmission is likely continuing in the epidemic zone, and with increased deforestation and population expansion, additional epidemics caused by Rocio virus are highly probable. If migratory species of birds are, or become involved in, the virus transmission cycle, the competency of a wide variety of mosquito species for transmitting Rocio virus experimentally suggest that the virus may become more widely distributed. The encephalitis outbreak in the western hemisphere caused by West Nile virus, a related flavivirus, highlights the potential for arboviruses to cause severe problems far from their source enzootic foci.

<i>Culex quinquefasciatus</i> Species of fly

Culex quinquefasciatus, commonly known as the southern house mosquito, is a medium-sized mosquito found in tropical and subtropical regions of the world. It is a vector of Wuchereria bancrofti, avian malaria, and arboviruses including St. Louis encephalitis virus, Western equine encephalitis virus, Zika virus and West Nile virus. It is taxonomically regarded as a member of the Culex pipiens species complex. Its genome was sequenced in 2010, and was shown to have 18,883 protein-coding genes.

Hart Park virus, or HP virus, is a single-stranded RNA arbovirus that is primarily transmitted through mosquitoes. The HP virus is classified in the Rhabdoviridae family and is related to the viral agents that cause rabies and vesicular stomatitis. The exact date of discovery of this virus is uncertain, but its presence in the entomological community dates back as far as 1964. Because of its relatively recent discovery, its exact effect on hosts is uncertain. Currently, there is no known disease affiliated with the Hart Park virus.

Jamestown Canyon encephalitis is an infectious disease caused by the Jamestown Canyon virus, an orthobunyavirus of the California serogroup. It is mainly spread during the summer by different mosquito species in the United States and Canada.

Spondweni virus is an arbovirus, or arthropod-borne virus, which is a member of the family Flaviviridae and the genus Flavivirus. It is part of the Spondweni serogroup which consists of the Sponweni virus and the Zika virus (ZIKV). The Spondweni virus was first isolated in Nigeria in 1952, and ever since, SPONV transmission and activity have been reported throughout Africa. Its primary vector of transmission is the sylvatic mosquito Aedes circumluteolus, though it has been isolated from several different types of mosquito. Transmission of the virus into humans can lead to a viral infection known as Spondweni fever, with symptoms that include headache, nausea, myalgia and arthralgia. However, as SPONV is phylogenetically close to the ZIKV, it is commonly misdiagnosed as ZIKV along with other viral illnesses.

<i>Aedes japonicus</i> Species of fly

Aedes japonicus, commonly known as the Asian bush mosquito or the Asian rock pool mosquito, was first described by Theobald in 1901 from Tokyo, Japan. They are competent arbovirus vectors known to transmit the West Nile virus as well as Japanese and St. Louis encephalitis. They are listed as an invasive species by the Global Invasive Species Database.

Royal Farm virus, previously known as Karshi virus, was not viewed as pathogenic or harmful to humans. Although infected people suffer with fever-like symptoms, some people in Uzbekistan have reported with severe disease such as encephalitis and other large outbreaks of fever illness connected infection with the virus.

<i>West Nile virus</i> Species of flavivirus causing West Nile fever

West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family Flaviviridae, from the genus Flavivirus, which also contains the Zika virus, dengue virus, and yellow fever virus. The virus is primarily transmitted by mosquitoes, mostly species of Culex. The primary hosts of WNV are birds, so that the virus remains within a "bird–mosquito–bird" transmission cycle. The virus is genetically related to the Japanese encephalitis family of viruses. Humans and horses both exhibit disease symptoms from the virus, and symptoms rarely occur in other animals.

<span class="mw-page-title-main">Palm Creek virus</span> Species of virus

Palm Creek virus (PCV) is an insect virus belonging to the genus Flavivirus, of the family Flaviviridae. It was discovered in 2013 from the mosquito Coquillettidia xanthogaster. The female mosquitoes were originally collected in 2010 from Darwin, Katherine, Alice Springs, Alyangula, Groote Eylandt, Jabiru and the McArthur River Mine, and had since been preserved. The discovery was made by biologists at the University of Queensland. The virus is named after Palm Creek, near Darwin, from where it was originally isolated.

References

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  2. McIntosh, Bruce M. (1985). "Usutu (SA Ar 1776), nouvel arbovirus du groupe B.". International Catalogue of Arboviruses. 3: 1059–1060.
  3. 1 2 3 4 5 6 7 8 9 10 11 M. Clé; C. Beck; S. Salinas; S. Lecollinet; S. Gutierrez; P. Van de Perre; T. Baldet; V. Foulongne; Y. Simonin (2019). "Usutu virus: A new threat?". Epidemiology and Infection . 147: E232. doi: 10.1017/S0950268819001213 . PMC   6625183 . PMID   31364580.
  4. Becker, Norbert; Petrić, Dušan; Zgomba, Marija; Boase, Clive; Madon, Minoo B.; Dahl, Christine; Kaiser, Achim (2020). "§ 3.2.2.6 Usutu virus". Mosquitoes: Identification, Ecology and Control (3rd ed.). Springer. p. 41. ISBN   978-3-030-11623-1.
  5. Worth, Charles Brooke (1971). Mosquito Safari: A Naturalist in Southern Africa. New York: Simon and Schuster. p. 303. ISBN   978-0-671-20827-1.
  6. Herbert Weissenböck; Tamás Bakonyi; Giacomo Rossi; Paolo Mani; Norbert Nowotny (2013). "Usutu Virus, Italy, 1996". Emerging Infectious Diseases . 19 (2): 274–277. doi: 10.3201/eid1902.121191 . PMC   3559058 . PMID   23347844.
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  9. "Blackbird numbers plummet as new mosquito-borne virus arrives in London". www.discoverwildlife.com. 6 June 2024. Retrieved 8 June 2024.