Serological Investigation of Phlebovirus Exposure in Blood Donors from the Mediterranean Province of Mersin, Turkey

Phleboviruses are enveloped segmented RNA viruses, capable of inducing febrile disease and/or meningoencephalitis in exposed individuals, according to the infecting strain, following transmission via arthropods. Prototype medically-important phlebovirus strains responsible for sandfly fever are sandfly fever Sicilian virus (SFSV) and sandfly fever Naples virus (SFNV), where the SFSV variant sandfly fever Cyprus virus (SFCV) is also detected in individuals with febrile disease. Toscana virus (TOSV) is unique among phleboviruses as the cause of infections involving central nervous system. In this seroepidemiological study, human exposure to selected medically-important phleboviruses was investigated in healthy adult residents of the Mersin province, Mediterranean Anatolia, Turkey, where the current data on phlebovirus epidemiology is scarce. A total of 1 784 healthy individuals (mean age: 34.7 9.6 years; 97.3% were male), accepted as blood donors at the Mersin University Center for Health Research and Application Blood Bank were included in the study after informed consent during a seventeen month period between July 2011 to November 2012. All participants were requested to fill out a questionnaire to reveal risk factors for vector exposure. SFSV, SFNV, SFCV and TOSV IgG antibodies in serum were investigated via a commercial indirect immunofluorescence test (RFT) (Sandfly Fever Virus IgG Mosaic I; Euroimmun, Germany). Sera interpreted as positive or strong positive for TOSV or SFNV+TOSV in IIFT were evaluated via TOSV virus neutralization test (VNT) for specificity confirmation. IIFT seroreactivity for at least one of the tested phleboviruses was present in 66.8% (1192/1784) of the samples. The most frequently-detected phlebovirus strain was SFSV (51.6%; 920/1784), followed by SFNV (46.4%; 827/1784), TOSV (43.7%; 779/1784) and SFCV (47.3%; 843/1784). Among the reactive sera, 6.6% (79/1192) were positive for a single virus serotype, whereas in 39.8% (475/1192) antibodies reacting with all tested virus serotypes were revealed. A total of 187 sera was included in the TOSV VNT and neutralizing antibodies were detected in 13.9%. According to the IIFT reactivity, residing in rural areas was observed as a statistically significant risk factor for exposure in all phleboviruses tested (p values for SFSV, SFNV, TOSV and SFCV were 0.002, 0.001, <0.001 and 0.003, respectively). TOSV exposure is more frequently detected via IIFT in individuals having pets or domestic farm animals around the living quarters (p= 0.005). As a result, frequent exposure to SFSV/SFCV or antigenically similar phlebovirus strains and viruses of the SFNV species were determined in healthy blood donors in Mersin province, located in the Mediterranean region of Turkey. Furthermore, TOSV neutralizing antibodies were detected in selected samples with IIFT reactivity, confirming previous reports suggesting TOSV activity in the region. TOSV and other phleboviruses must be included in the diagnostic work-up in cases with febrile diseases and viral central nervous system infections during the sandfly-active months.