Serologic, molecular, and pathologic survey of pseudorabies virus infection in hunted wild boars (sus scrofa) in Italy.

During the hunting season of 2010-2011, blood samples, nasal and genital swabs and tonsillar and lymph node tissue samples were collected, in Tuscany, Central Italy, from 139 wild boars (39 piglets, 30 juveniles and 70 adult subjects), to investigate pseudorabies virus (PrV) seroprevalence and viral DNA presence. Immunohistochemistry with anti-PRV monoclonal antibodies was performed on selected tissue samples. Forty-three of 139 (30.9%) subjects were PrV-seropositive, while a 1954 base pair PrV specific product was amplified from 9 nasal (6.5%) and 26 genital (18.7%) swabs. Sequence analysis of PrV-positive PCR products revealed identity scores ranging from 99 to 100% with Suid herpesvirus 1 strain Becker (JF797219) and confirmed the identification of PrV DNA in tested swabs. Significantly higher seroprevalence was observed in adult subjects than in juveniles (P<0.001) and in piglets than in juveniles (P<0.05). The viral DNA presence was significantly higher in genital swabs than in nasal specimens (P<0.001). The percentage of positive nasal swabs did not differ in the different age groups considered. Piglets had a higher percentage of virus-positive genital swabs than juvenile and adult subjects (30.8% vs 13.3% and 14.3%, respectively). The results confirmed that PrV infection is widespread in the wild boar population in the studied area. The presence of anti-PrV antibodies and of the PrV virus in piglets could be related to a vertical transmission of the virus, this hypothesis was also supported by an higher presence of viral genome in genital swabs than in nasal ones. This field study seems to confirm the importance of vertical transmission of PrV and in adult feral boars the preferential transmission through the venereal route due to the higher percentage of virus-positive genital swabs.