Toscana Virus

Toscana Virus Background

Toscana virus (TOSV) or Sandfly fever Naples phlebovirus (SFNV) is a member of the genus Phlebovirus of the family Bunyaviridae. TOSV is an enveloped, single-stranded, negative-sense RNA virus. The viral genome is segmented, having three segments that are referred to as large (L), medium (M) and small (S). These segments encode the viral RNA-dependent RNA polymerase, envelope glycoproteins, nucleoproteins and non-structural proteins. Two genotypes of TOSV have been identified, which are referred to as lineage A and lineage B. However, some reports suggest that there may be additional lineages of the virus in circulation (Cusi, MG).

TOSV is an arthropod-borne virus that is transmitted by sandfly of the Phlebotomus species, including Phlebotomus perniciosus and Phlebotomus perfiliewi. Since the virus was first isolated from sandfly in 1971, no bird or small mammal reservoir has been reliably identified, suggesting that infected sandfly may act as vector and reservoir for TOSV. The disease caused by TOSV is prevalent during the summer months when the sandfly is most abundant (Charrel, RN). Although initially isolated in Italy, Toscana virus is now geographical widespread throughout the Mediterranean region including Italy, France, Spain, Portugal, Greece, Croatia, Cyprus and Turkey.

TOSV is a serotype of Sandfly-fever viruses, with a neuroinvasive nature. The virus causes a febrile illness called pappataci-fever (or Sandfly-fever) but can also cause neurological disease including aseptic meningitis, encephalitis or meningoencephalitis. In many cases, TOSV infection is asymptomatic or presents as a self-limiting febrile illness. However, some patients develop a range of neurological symptoms which include meningitis like symptoms, headache, neck-stiffness, nausea, vomiting, myalgia and weakness. Other neurological symptoms have been reported including deafness, speech disorders and paresis.

In Europe, TOSV represents an important emerging pathogen that has the potential to spread to countries outside the Mediterranean. The virus is a significant cause of aseptic meningitis in endemic areas. Currently, there is no antiviral therapy for the treatment of symptomatic cases of TOSV, and no licensed prophylactic vaccine to prevent TOSV infection. Diagnosis of TOSV in humans is achieved using molecular methods to detect the virus or serological methods to measure Toscana virus specific IgM levels in infected patients.

References

Cusi MG, Savellini GG, Zanelli G.2010.Toscana virus epidemiology: from Italy to beyond. Open Virol J. 2010 Apr 22;4:22-8.

Charrel RN, Bichaud L, de Lamballerie X.2012.Emergence of Toscana virus in the Mediterranean area. World J Virol. 2012 Oct 12;1(5):135-41.