Toscana virus in the Portuguese population: serosurvey and clinical cases.

Abstract

Toscana virus (Phlebovirus genus, Bunyaviridae family) is a neurotropic virus which circulates in the Mediterranean Basin. Although Portugal has been the second country where its presence was reported, the existence of this virus in our country has been referred only sporadically, and there is a lack of knowledge regarding the prevalence of antibodies in the population. Thus, the objective of this study was to analyse the prevalence of antibodies anti-Toscana virus in the human population in our country. Sero-epidemiological investigations were performed with indirect immunofluorescence assay (IFA) and enzyme linked immunosorbent assay (ELISA) tests. The study population consisted of a control population (blood donors, n=150), a population considered at risk (n=236) and a population of individuals with symptoms and laboratory diagnostic request for vector-borne viruses. The latter population was divided into two groups: those individuals with neurological symptoms (n=165) and those without neurological symptoms (n=373). We tested sera from a total of 924 individuals. The seroprevalence of IgG antibodies in the control population was 2%. In the population considered at risk, the prevalence was 3.4%. In the population with central nervous system disease, we detected a seroprevalence of 4.2%. For the same type of antibodies and in subjects without central nervous system disease, the prevalence was 1.3%. Five cases of recent infection (3%) were detected in the population with neurological signs. Those infections have been acquired in the districts of Faro, Coimbra, Aveiro and Lisbon. The associated clinical diagnoses were meningitis, meningoencephalitis and rash. The observed seroprevalences were, in general, lower than reported in other endemic countries. Only 5 of the 29 sera which gave positive results by IFA and ELISA were confirmed by plaque reduction neutralization tests with the Italian strain ISS.Phl.3. This can indicate the presence of more than one Toscana virus serotype circulating in Portugal and emphasizes the need for more research about this etiological agent in our country.