Expert comment: Recalled Cadbury chocolate desserts

Dr Simon Clarke, University of Reading said: “Listeria is a bacteria that can contaminate foodstuffs, commonly those containing dairy. People consuming contaminated foods are at risk of infection. So, it isn’t out of the question that these types of products – chocolate pudding style desserts – could become contaminated. However, food production is heavily regulated in the UK and all dairy products are screened for harmful micro-organisms.

“There are several methods of testing for Listeria, with some giving results quicker than others. Typically, there is an initial test that gives an indicative result and hence we might say that there is a “possible presence” of Listeria. Following this, a more detailed test can confirm Listeria and quantify the extent of the contamination.

“It is sensible to swiftly recall all the products that relate to the positive test sample, even before the presence of Listeria is completely confirmed. Listeria can cause serious disease and disability so putting public health first is the only ethical approach to the problem. If that is what has happened in this case, that is a good thing.

“Listeria is often found in the environment, but cases of illness are fairly rare – each year there are perhaps 100-200 cases in the UK. Generally, the classic food poisoning symptoms diarrhoea and/or vomiting are an indication of mild disease, but it can be much more serious than that. The pathogen can use our guts as a gateway to our bloodstream where in people with weakened immune systems, like cancer patients, the elderly and very young, it can spread to our organs, including the brain, which can be fatal. Unusually, it’s also one of the few bacteria that, when causing an infection, can cross the placenta and infect an unborn baby often causing lifelong disability if the infection is not fatal.”