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

Abstract

Toscana virus (TOSV) is a Phlebovirus transmitted by phlebotomine sand flies and is an important etiological agent of summer meningitis in the Mediterranean basin. Since TOSV infection is often asymptomatic, we evaluated the seroprevalence in blood donors (BDs) in the Bologna and Ferrara provinces (Northeastern Italy)—the areas with the highest and lowest numbers of TOSV neuroinvasive cases in the region, respectively. A total of 1208 serum samples from BDs were collected in April–June 2014 and evaluated for the presence of specific TOSV-IgG by ELISA. The IgG-reactive samples were confirmed by indirect immunofluorescence assay (IIF) and by microneutralization test (MN). Serum samples were defined as positive for anti-TOSV IgG when reactive by ELISA and by at least one second-level test; TOSV seroprevalence was 6.8% in the Bologna province, while no circulation of TOSV was detected in the Ferrara province. Sand fly abundance in 2014 was also estimated by a geographic information system using a generalized linear model applied to a series of explanatory variables. TOSV seroprevalence rate was strongly associated with the sand fly abundance index in each municipality, pointing out the strong association between sand fly abundance and human exposure to TOSV.

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

“…The positive pools were collected in the sites where the most sand flies were collected. This data seems to confirm a possible relationship between the abundance of sand flies and the circulation of the pathogens they transmit, as already hypothesized for TOSV on a serological basis [ 31 ] and already observed in sand flies collected at one site for L. infantum and phleboviruses [ 9 ]. In this case, the relationship between dry season and abundance of sand flies would also involve a higher circulation of pathogens, an association already made in a study of a leishmaniasis outbreak recorded in Emilia-Romagna in 1970 [ 7 , 32 ].…”

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

“…A similar relation has been shown for Lutzomyia species in South America [ 25 , 26 ]. As already noted in this area of Italy, the abundance of sand flies directly affected the circulation of Toscana virus [ 27 ]. Similarly, the recrudescence of human Leishmaniasis was recorded in the Emilia-Romagna region after seasons with abundant captures of sand flies, such as in 2013–2014 [ 6 , 28 ].…”