Detection of Specific Antibodies against Toscana Virus among Blood Donors in Northeastern Italy and Correlation with Sand Fly Abundance in 2014

Seroprevalence of Toscana virus in blood donors in mainland Portugal

BACKGROUND

Toscana virus (TOSV; Phlebovirus toscanaense), a phlebovirus transmitted by sand flies, is a growing public health concern in the Mediterranean region, with infections often being asymptomatic but potentially leading to neuroinvasive disease. Despite its presence in neighboring countries, data on TOSV seroprevalence in Portugal are limited. This study aimed to estimate the national seroprevalence of TOSV among blood donors in mainland Portugal and explore associations with sociodemographic factors and Leishmania infection.

METHODS

A cross-sectional study was conducted using serum samples from 3593 blood donors across mainland Portugal, collected between February and June 2022. Anti-TOSV antibodies were detected via microneutralization assay, and anti-Leishmania antibodies had previously been tested using ELISA. Sociodemographic data were obtained from self-administered questionnaires. Seroprevalence was estimated by region, and multivariate logistic regression was used to identify factors associated with TOSV infection.

RESULTS

Overall, the estimated national true seroprevalence of TOSV was 2.6% (95% CI 2.1-3.1%). Regional seroprevalence varied significantly, with the highest values (up to 14.8%) in Alto Alentejo, Baixo Alentejo, Douro, Alto Tâmega e Barroso and Oeste regions. Multivariate analysis showed that age ≥ 50 years (aOR 1.70, 95% CI 1.04-2.77), residing in the Alentejo region (aOR 3.05, 95% CI 1.85-5.02) and positive/borderline Leishmania serology (aOR 2.31, 95% CI 1.29-4.15) were significantly associated with TOSV infection.

CONCLUSIONS

This study highlights new areas of TOSV circulation in Portugal, particularly in regions with higher Leishmania seroprevalence and visceral leishmaniasis incidence, suggesting co-circulation of these pathogens. Although a lower seroprevalence was obtained compared to neighboring countries, TOSV should still be considered in the differential diagnosis of viral meningitis and encephalitis in Portugal, especially in potentially high-risk regions. Further research is needed to better understand the ecological drivers of TOSV distribution in Portugal.

Sand Flies and Pathogens in the Lowlands of Emilia-Romagna (Northern Italy)

Cases of sand fly-borne diseases in the Emilia-Romagna region, such as meningitis caused by Toscana virus and human leishmaniasis, are reported annually through dedicated surveillance systems. Sand flies are abundant in the hilly part of the region, while the lowland is unsuitable habitat for sand flies, which are found in lower numbers in this environment with respect to the hilly areas. In this study, we retrieved sand flies collected during entomological surveillance of the West Nile virus (from 2018 to 2021) to assess their abundance and screen them for the presence of pathogens. Over the four-year period, we collected 3022 sand flies, more than half in 2021. The most abundant sand fly species was Phlebotomus (Ph.) perfiliewi, followed by Ph. perniciosus; while more rarely sampled species were Ph. papatasi, Ph. mascittii and Sergentomyia minuta. Sand flies were collected from the end of May to the end of September. The pattern of distribution of the species is characterized by an abundant number of Ph. perfiliewi in the eastern part of the region, which then falls to almost none in the western part of the region, while Ph. perniciosus seems more uniformly distributed throughout. We tested more than 1500 female sand flies in 54 pools to detect phleboviruses and Leishmania species using different PCR protocols. Toscana virus and Leishmania infantum, both human pathogens, were detected in 5 pools and 7 pools, respectively. We also detected Fermo virus, a phlebovirus uncharacterized in terms of relevance to public health, in 4 pools. We recorded different sand fly abundance in different seasons in Emilia-Romagna. During the season more favorable for sand flies, we also detected pathogens transmitted by these insects. This finding implies a health risk linked to sand fly-borne pathogens in the surveyed area in lowland, despite being considered a less suitable habitat for sand flies with respect to the hilly areas.

Co-Circulation of Phleboviruses and Leishmania Parasites in Sand Flies from a Single Site in Italy Monitored between 2017 and 2020

Sand flies transmit Leishmania infantum, which is responsible for causing leishmaniasis, as well as many phleboviruses, including the human pathogenic Toscana virus. We screened sand flies collected from a single site between 2017 and 2020 for the presence of both phleboviruses and Leishmania. The sand flies were sampled with attractive carbon dioxide traps and CDC light traps between May and October. We collected more than 50,000 sand flies; 2826 were identified at the species level as Phlebotomus perfiliewi (98%) or Phlebotomus perniciosus (2%). A total of 16,789 sand flies were tested in 355 pools, and phleboviruses were found in 61 pools (6 Toscana virus positive pools, 2 Corfou virus positive pools, 42 Fermo virus positive pools, and 7 Ponticelli virus positive pools, and 4 unidentified phlebovirus positive pools). Leishmania was found in 75 pools and both microorganisms were detected in 16 pools. We isolated nine phleboviruses from another 2960 sand flies (five Ponticelli viruses and for Fermo viruses), not tested for Leishmania; the complete genome of a Fermo virus isolate was sequenced. The simultaneous detection in space and time of the Fermo virus and L. infantum is evidence that supports the co-circulation of both microorganisms in the same location and partial overlap of their cycles. A detailed characterization of the epidemiology of these microorganisms will support measures to limit their transmission.

Epidemiology of Toscana virus in South Tuscany over the years 2011-2019

BACKGROUND

Toscana virus (TOSV) is a Phlebovirus transmitted to humans by phlebotomines and represent an etiological agent of acute aseptic meningitis (AAM) in countries where the virus is endemic, including Italy. Incidence of TOSV infections is closely associated with the geographical distribution of the phlebotomine vectors which in turn is affected by climate changes that determine survival and spread. As a result, TOSV infections show a seasonal trend with a peak of incidence in summer months.

OBJECTIVES

To measure the prevalence of TOSV infections in AAM patients in central Italy and evaluate the climate changes in phlebotomine vectors ecology and virus propagation.

STUDY DESIGN

One thousand and seventy-three cerebrospinal fluid samples (CSFs), collected from patients with suspected viral meningitis, were collected over nine years (2011-2019) during the May to October period and tested for viruses most commonly associated with AAM. Serum samples addressed to the Microbiology and Virology Unit of "S. Maria delle Scotte" Hospital for confirmation acute TOSV infection (n = 324) were tested for TOSV-specific IgM and IgG.

RESULTS

Among the CSF samples, 1.3% were positive for Enteroviruses; 0.9% for Varicella zoster virus, 1.9% for Herpes simplex virus type-1/2 and 4.6% for TOSV. Serum IgM analyses disclosed TOSV-specific IgM in 27.1% of sera suggesting the predominant involvement of TOSV in neuroinvasive infections.

CONCLUSIONS

This data confirms the predominant role of TOSV as causative agent of AAM during the summer time in endemic countries. Moreover, climate changes affecting phlebotomine vectors persistence, reproduction and activity could be involved in the cyclic nature of TOSV infection reported during the last nine years.