Emergence of Toscana Virus, Romania, 2017-2018

Toscana virus: A comprehensive review of 1381 cases showing an emerging threat in the Mediterranean regions

BACKGROUND

Toscana virus (TOSV) is a sand fly-borne phlebovirus causing central nervous system (CNS) infection in Mediterranean countries, during summer season. However, clinical aspects of the disease caused by this virus are poorly known by clinicians, so that its prevalence is probably underestimated due to a lack of diagnosis.

STUDY DESIGN

The data was gathered from all available case series and retrospective studies identifying TOSV as the causative viral agent. The informations of age, sex, clinical characteristics, laboratory findings, imaging results and clinical outcomes of TOSV infection were recorded and analyzed.

RESULTS

A total of 95 articles including TOSV infections resulting in a total of 1381 cases, were analyzed. Our findings indicate that TOSV affects individuals across various age groups, with a median age of 44.45 years. A notable disparity in infection rates between genders, with men being significantly more likely to present symptoms due to TOSV than women, with a sex ratio of 2.0. The clinical presentation of TOSV infection encompasses a range of symptoms, including fever, headache, retro-orbital pain, neurological and muscular manifestations with less common reports of cutaneous and gastrointestinal symptoms. To date, six fatalities have been attributed to TOSV infections, with a median age of 76 years. Diagnostic evaluation of TOSV infections often involves the analysis of cerebrospinal fluid, where findings may include an elevated white blood cell count.

CONCLUSIONS

These findings underscore the diverse clinical manifestations of TOSV infections including flu like symtomps. TOSV is an emerging infectious threat that warrants inclusion in the diagnostic protocols for patients presenting with CNS, particularly within the Mediterranean basin or for those with recent travel history to endemic regions during warmer months when sand flies are actively circulating.

Toscana virus - an emerging Mediterranean arbovirus transmitted by sand flies

Toscana virus (TOSV) is an emerging arthropod-borne virus (arbovirus) of medical importance that is increasing its range across much of the Mediterranean Basin, Europe and the Middle East. Transmitted by Phlebotomus spp. sand flies, it is the most clinically relevant sand fly-borne phlebovirus. Initially isolated in the Tuscany region of Central Italy, it has now been detected in multiple countries that surround this geographical area. Infection of the vertebrate host can cause fever and neurological disease, following the dissemination of the virus to the brain. The prevalence is high in some regions, with a notable percentage of individuals showing seroconversion. TOSV can be a leading cause of acute meningitis and encephalitis (AME) during the summer months. In this comprehensive review, we will focus on several key topics. We discuss how TOSV has spread to establish outbreaks of infection in both humans and animals around the Mediterranean and the wider region. Clinical aspects of TOSV infection in humans are described, along with the best standards in diagnosis. Finally, we focus our discussion on the role of the sand fly vector, describing their biology, vector competency, implications for putative vertebrate reservoirs, the effect of the climate emergency on sand fly distribution and the putative role that sand fly-derived salivary factors may have on modulating host susceptibility to TOSV infection.

Toscana Virus in Wild-Caught Sand Flies in Portugal, Findings from the National Vector Surveillance Network, 2023

Phlebotomine sand flies play a crucial role in both human and veterinary medicine, acting as vectors for Leishmania parasites and most known phleboviruses. In Portugal, the REVIVE program, a comprehensive national surveillance network under the Ministry of Health, has included sand fly surveys since 2016. REVIVE aims to identify existing sand fly species in the country, determine which pathogens are circulating among them, and provide actionable insights for prevention and control measures when necessary. In this way, annually, from May to October, health technicians collect sand flies across mainland Portugal with CDC light traps. The collected sand flies are sent to the Centre for Vectors and Infectious Diseases Research for species identification and molecular screening of pathogens. On 21 September 2023, Toscana virus (TOSV), a well-known phlebovirus in the Mediterranean region due to its capacity to cause neurological disease, was detected in a pool of 30 sand flies collected in Algarve, the southernmost region of Portugal. A 668 bp partial sequence of the nucleoprotein gene shows similarity with TOSV strains from Spain. To our knowledge, this is the first detection of TOSV in its vector in this country, having previously only been reported in vertebrate hosts. These findings highlight the important role of ongoing surveillance efforts in monitoring and understanding the dynamics of sand fly-borne diseases in Portugal.

Prevalence of Toscana Virus Antibodies in Residents of Bulgaria: A Nationwide Study Following the Pandemic of COVID-19

Introduction: Toscana virus (TOSV) is an arthropod-borne virus transmitted by sandflies and is mainly found in countries around the Mediterranean basin. In this article, we present the findings of a seroprevalence study on TOSV in Bulgaria. We aim to assess the current epidemiological situation regarding TOSV in the country and raise clinical awareness. Methods: Serum samples (n = 1892) were collected in December 2023. Serological tests were performed using a commercial anti-TOSV ELISA kit. Results: Specific immunoglobulin G (IgG) antibodies were detected in 6.4% (121/1892) of the participants. A significantly higher seropositivity rate was found in the age group over 65 years compared with the age groups 18-29 and 40-64 (11.8% vs. 3.9% vs. 3.4%), as well as in males compared with females (8.0% vs. 5.3%). The seroprevalence rates in districts ranged from 0% to 18.5%. Higher seropositivity was found in the southern and northern regions. Conclusions: The seroprevalence rate of TOSV in Bulgaria, found in this study, is a significant decrease compared with the seropositivity rate of 24.5% reported in the country in 2018. The reasons for this are unknown and could possibly be related to the COVID-19 pandemic and the constantly changing environmental conditions. There is also a possibility that the higher seropositivity detected in 2018 together with the rise in clinical cases reported from endemic countries around that time might have been due to an unrecognized TOSV outbreak taking place in this period. Continued clinical awareness and surveillance are necessary for recognition and management of potential cases of TOSV neuroinfection, especially during summer.

Toscana virus (TOSV) meningitis with atypical characteristics: Report of two cases

Toscana virus (TOSV) is an emerging cause of central nervous system (CNS) infections, especially in endemic countries during summer. Cerebrospinal fluid (CSF) is usually clear, with < 500 leukocytes/mm3, normal glucose (> 60 % serum glucose) and normal (< 45 mg/dL) to slightly increased protein levels. Here we present two cases of TOSV meningitis with misleading CSF characteristics observed at Santa Maria Annunziata Hospital (Bagno a Ripoli, Florence, Italy). Case 1 presented with signs and symptoms of meningitis. CSF was opalescent on macroscopic examination, with 1192 cells/mm3, hypoglycorrhachia (30 % serum glucose) and hyperproteinorachia (228.0 mg/dL). TOSV meningitis was confirmed with serology. Case 2 presented with headache, vomiting and mild neck stiffness. CSF was slightly turbid, with 1092 cells/mm3, normal glucose (61 % serum glucose) and slightly increased protein (77.0 mg/dL) levels. TOSV meningitis was confirmed with serology and molecular test on CSF. We performed a literature review including cases of TOSV neuroinvasive infections in which CSF characteristics were reported. Pleocytosis > 500 cells/mm3 was reported in 12/62 (19.4 %) patients, hypoglycorrhachia in 3/62 (4.8 %) patients, mild hyperproteinorachia (45 - 75 mg/dL) in 7/62 (11.3 %) patients and severe hyperproteinorachia (> 75 mg/dL) in 40/62 (64.5 %) patients. TOSV should be considered in the differential diagnosis of CNS infections in endemic areas during the warm season even when CSF examination shows atypical results.

Co-Circulation of Leishmania Parasites and Phleboviruses in a Population of Sand Flies Collected in the South of Portugal

In the Old World, phlebotomine sand flies from the genus Phlebotomus are implicated in the transmission of Leishmania spp. parasites (Kinetoplastida: Trypanosomatidae) and viruses belonging to the genus Phlebovirus (Bunyavirales: Phenuiviridae). Two of the five sand fly species known to occur in Portugal, Phlebotomus perniciosus and Ph. ariasi, the former being the most ubiquitous, are recognized vectors of Leishmania infantum, which causes visceral leishmaniasis, the most prevalent form of leishmaniasis in the country. Phlebotomus perniciosus is also the vector of the neurotropic Toscana virus, which can cause aseptic meningitis. Entomological surveillance is essential to provide fundamental data about the presence of vectors and the pathogens they can carry. As such, and given the lack of data in Portugal, an entomological survey took place in the Algarve, the southernmost region of the country, from May to October 2018. Polymerase chain reaction assays were performed in order to detect the presence of the above-mentioned pathogens in sand fly pools. Not only were both Leishmania parasites and phleboviruses detected during this study, but more importantly, it was the first time their co-circulation was verified in the same sand fly population collected in Portugal.

Sandfly-Borne Phleboviruses in Portugal: Four and Still Counting

According to ICTV, there are currently 66 known phlebovirus species. More than 40 of these viruses were isolated or detected in phlebotomine sandflies and some of them are known pathogens. In Portugal, information about sandfly-borne phleboviruses is scarce and scattered sandfly-borne diseases are neglected and often not considered in differential diagnoses. The main objective of this work was to gather the existing information and to raise awareness about the circulating phleboviruses in this country. To date, Massilia and Alcube phleboviruses have been isolated from sandflies in southern Portugal. Human infections with Toscana and Sicilian phleboviruses have been reported, as well as seroprevalence in cats and dogs. More studies are needed in order to understand if the viruses isolated during the entomological surveys have an impact on human health and to fully understand the real importance of the already recognized pathogens in our country.

Seroprevalence Rates against West Nile, Usutu, and Tick-Borne Encephalitis Viruses in Blood-Donors from North-Western Romania

Introduction: West Nile virus (WNV), Usutu virus (USUV), and the tick-borne encephalitis virus (TBEV) are all arboviruses belonging to Flaviviridae family. All are characterized by vectorial transmission and sometimes associated with neuroinvasive infections. The circulation of these viruses is considered endemic in parts of Europe, with human cases reported in many countries. Among hosts, the viruses are vectored by hematophagous arthropods, such as mosquitoes (WNV, USUV) and ticks (TBEV). Considering the currently outdated knowledge regarding the epidemiology of these viruses in Romania, the aim of our study was to assess the seroprevalence rates of WNV, USUV, and TBEV among healthy blood donors in north-western Romania. Methods: Human blood samples from healthy donors were collected between November 2019 and February 2020 in six counties from the north-western region of Romania. The samples were serologically tested by ELISA and serum neutralization test. Results: Overall, we obtained a seroprevalence of 3.17% for WNV, 0.08% for TBEV, and 0% for USUV. Conclusion: Despite the low seroprevalence of WNV, USUV, and TBEV in our study, we highlight the need for continuous nationwide vector and disease surveillance and implementation of control measures. Further research is required for an optimal overview of the epidemiological status of the Romanian population regarding these flaviviruses together with countrywide awareness campaigns.