The zoonotic hepatitis E virus genotype 3 (HEV-3) is the causative agent of HEV-3 infections in humans. The primary route of transmission occurs from pigs to humans, via the consumption of contaminated (ready-to-eat) raw meat products such as dried sausage or liver. Meat products are often subjected to different industrial food-processing techniques such as fermentation, acidification, high-pressure processing or thermal treatments, of which the latter one can also be performed by the consumer at home. With the exposure of pork products to different temperatures for different durations, HEV-3 that may be present in these pork products is exposed to these conditions as well. The effects of thermal treatment on the presence of HEV using molecular RNA detection techniques have previously been described. However, these techniques do not discriminate between the presence of infectious and inactivated virus, which is required to assess associated public health risks. Therefore, detection methods that quantify infectious HEV in raw pork products are needed.
The study by dr. Rutjes, dr. Stunnenberg and team focused on the development of an assay that could semi-quantitatively detect the presence of infectious HEV-3 in pork products. To do so, they implemented the cell culture method by dr. Johne et al. that was previously developed to detect infectious HEV in cell culture media to detect infectious HEV in inoculated dried sausages and liver. Next, Rutjes and team assessed HEV infectivity in these inoculated pork products after exposure to a wide range of conditions mimicking food-processing temperatures. A Bayesian MPN modelling approach was used to estimate HEV-3 inactivation.
The researchers found that HEV remained infectious in pork products during different food-processing temperatures. For instance, HEV-3-containing dried sausage subjected to 21 °C and lower temperatures (15, 10 and 4 °C) for 4 weeks still contained infectious HEV-3. Furthermore, infectious HEV-3 was detected in liver that was exposed to 55 °C for 2 hours as well as 65 °C for 1 hour. Full HEV inactivation was observed after treatment with 71 °C for 5 minutes. Importantly, this semiquantitative infectivity assay was successful in the detection and estimation of infectious HEV concentrations in livers from naturally infected pigs.
These findings provide valuable insight into the effect of different thermal food-processing conditions used by industry and the consumer on the inactivation of HEV-3 in pork matrices. Ultimately, these findings contribute to the evaluation of the risk of HEV-3 infection through the consumption of HEV-contaminated pork products.
This study was published in Microorganisms in September 2023. Publication link: https://doi.org/10.3390/microorganisms11102451
