Molecular epidemiology of canine adenovirus type 1 and type 2 in free-ranging red foxes (Vulpes vulpes) in Italy

To date, no studies exist regarding the presence of canine adenovirus (CAdV) infection in foxes in Italy. Furthermore, the majority of worldwide investigations regarding the presence of CAdV in foxes have been carried out using common serological assays which are unable to differentiate between CAdV type 1 and CAdV type 2. To assess the presence of viral infection in Italian red foxes (Vulpes vulpes), thirty-two subjects shot during the regular hunting season in the province of Pisa (Tuscany, Italy) were sampled and tested using a polymerase chain reaction (PCR) assay capable of distinguishing between CAdV type 1 and type 2. Two subjects were positive for CAdV-1 infection and one other for CAdV-2 infection. Sequence analysis of the two CAdV-1 viruses showed complete identity between them and a high genetic similarity with all reference strains sequenced in dogs in the last twenty years, indicating the presence of genetically stable CAdV-1 in red foxes in Italy which could easily be transmitted from the wild animal population to domestic dogs. Therefore, this is the first reliable identification of CAdV-2 in foxes, and cloning of the virus detected has revealed a possible coinfection involving two different CAdV-2 strains, raising new questions about the pathogenic role of CAdV-2 in wildlife. The presence of CAdV-1 and CAdV-2 infection in foxes could represent a problem for both wild animals and domestic dogs, and emphasises the central role of red foxes in maintaining these viruses in the territory.