Comparison of methods for the detection of rotavirus in food; experiments with bovine rotavirus as surrogate for norovirus.

Norovirus has emerged as the most common cause of non bacterial gastroenteritis in humans. In Germany, a total of 200792 human norovirus have been notified in 2007 (Robert-Koch-Institut, 2008). Noroviruses are transmitted from person to person by faecal-oral route, either directly or indirectly via contaminated surfaces, food, and water. With an infectious dose of 10-100 virus particles, infectivity of norovirus is very high. Detection of viruses in food and environmental samples and hence identification of routes of transmission is difficult and currently not standardised. The object of our study is therefore to establish and standardise present methods of virus detection in food and environmental samples to identify possible routes of transmission. Bovine rotavirus was used as a surrogate for norovirus to compare different detection systems for viruses in representative foods of plant and animal origin. This virus was chosen due to the availability of cell culture systems for determination of infectivity which is not possible for noroviruses. In addition, rotaviruses are also known to be transmitted via food. Known concentrations of bovine rotavirus were deposited onto ham, sausage, pepper, apple, cucumber, lettuce and berries following examination by surface swabbing, ultrafiltration and an elution-precipitation method. Preliminary results have shown that the elution-precipitation method is suitable for the detection of rotavirus in lettuce and berries. Swabbing is an applicable method for virus detection in food with hard and smooth surfaces such as ham, sausage, pepper, apple and cucumber. Ultrafiltration is an appropriate method for virus detection in ham and lettuce. Methods described in this presentation were found satisfactory, and are proposed as appropriate methods for virus detection in foods. With additional refinement, these methods may be used by regional laboratories for testing foods for viral contamination and help to identify possible routes of transmission within epidemiological outbreak investigations. However, efficiency of methods, especially in the case of berries, has to be increased in further studies. Also reproducibility experiments as well as method validation on foods implicated in food-borne outbreaks are needed.