Comparison of two extraction methods for the detection of hepatitis A virus in lettuces using the murine norovirus as a process control

Enteric viruses are important agents of foodborne diseases. In recent years, raw fruits and vegetables have frequently been involved in foodborne transmission of enteric viruses to humans, particularly noroviruses and hepatitis A virus (HAV). Although viral contamination can occur at any stage of food processing, primary production is a critical stage in which prevention measures are essential to minimise the risk of infection to consumers. Due to the low infectious doses and low concentrations of enteric viruses in food samples, an efficient and rapid virus concentration method is required for routine control and risk assessment. In this study, the virus concentration reference method proposed by the CEN/TC275/WG6/TAG4 working group for samples of soft fruits and salad vegetables was compared with a method including a filtration step in order to recover hepatitis A virus (HAV) on lettuces. Murine norovirus (MNV-1) was used as a process control and detected simultaneously with HAV in a one-step duplex RT-qPCR following both procedures. The HAV LOD ranged from 10 to 100 PFU/25 g of lettuce in the presence or absence of MNV-1, regardless of method used. In conclusion, MNV-1 offers a very reliable and simple way to monitor the quality of the detection procedures. Although it has been found that both methods achieved an identical limit of detection, the method including a filtration step requires less processing and could be proposed as an alternative method.