Detection of porcine torovirus by real time RT-PCR in piglets from a Spanish farm

Toroviruses are enteric viruses belonging to the Nidovirales order that infect different animal species and humans. The lack of "in vitro" culture systems for toroviruses, except for the prototype Berne virus or BEV, isolated originally from an infected horse, has hampered their study and the development of diagnostic assays. This report describes a real time RT-PCR method to detect porcine torovirus (PToV) RNA in clinical fecal samples using primers corresponding to the gene coding for the nucleocapsid protein which are conserved in all PToV strains known to date. This method can be used to determine viral loads allowing quantitation within a range between 10(1) and 10(8) genomic units per reaction tube. The assay was evaluated with 48 rectal swabs from piglets from a Spanish farm. Nineteen out of 48 animals were shedding virus at the time of sample collection, indicating a high incidence of PToV infection in this farm. This is the first report showing the presence of PToV in Spain. The real time RT-PCR assay described in this report provides a rapid, highly sensitive, specific and reliable detection and quantitation method enabling future PToV epidemiological studies.