The actin gene was amplified using the outer primers previously used in a nested polymerase chain reaction (PCR), i.e. primers Tv8S (5′-TCT GGA ATG GCT GAA GAA GAC G-3′) and Tv9R (5′-CAG GGT ACA TCG TAT TGG TC-3′) , with the following thermocycling conditions: 5 min at 95 °C, 40 cycles of 30 s at 95 °C, 30 s at 55 °C and 3 min at 72 °C, followed by 7 min at 72 °C. This was performed on the ABI Veriti thermocycler platform (ThermoFisher Scientific, Waltham, Massachusetts, USA).