Toscana virus (TOSV) is an arthropod-borne virus, transmitted to humans by phlebotomine sandflies. Although the majority of
infections are asymptomatic, neuroinvasive disease may occur. We report three cases of neuroinvasive TOSV
infection detected in Croatia. Two patients aged 21 and 54 years presented with
meningitis, while a 22-year old patient presented with
meningoencephalitis and right-sided brachial plexitis. Cerebrospinal fluid (CSF), serum, and urine samples were collected and tested for neuroinvasive arboviruses:
tick-borne encephalitis, West Nile, Usutu, TOSV, Tahyna, and Bhanja virus. In addition, CSF and serum samples were tested for the anti-viral
cytokine response. High titers of TOSV
IgM (1000-3200) and
IgG (3200-10,000)
antibodies in serum samples confirmed TOSV
infection.
Antibodies to other phleboviruses (
sandfly fever Sicilian/Naples/Cyprus virus) were negative. CSF samples showed high concentrations of
interleukin 6 (IL-6; range 162.32-2683.90 pg/mL),
interferon gamma (IFN-γ; range 110.12-1568.07 pg/mL), and
IL-10 (range 28.08-858.91 pg/mL), while significantly lower
cytokine production was observed in serum. Two patients recovered fully. The patient with a brachial plexitis improved significantly at discharge. The presented cases highlight the need of increasing awareness of a TOSV as a possible cause of
aseptic meningitis/
meningoencephalitis during summer months. Association of TOSV and brachial plexitis with long-term sequelae detected in one patient indicates the possibility of more severe disease, even in young patients.