University of Manchester and Health Protection Agency researchers have shown that cancer patients have a five-fold increased risk of developing listeria than people with other underlying conditions.
The study, published in the journal Emerging Infectious Diseases today (Wednesday), also showed that those with cancers of the blood have the greatest risk.
Listeriosis is a rare but serious food-borne illness caused by the bacterium Listeria monocytogenes. Some groups of people can be more seriously affected by this type of food poisoning than others. Pregnant women and their unborn or newborn babies are at most risk, as well as the elderly and those with conditions that affect their immune system,
The incidence of listeria has increased in recent years, with 2.1 cases per million of the population between 1990 and 2000 to 3.6 cases per million in the period 2001 and 2009. This increase also revealed greater numbers of cases in people over 60 years of age. Similar increases have also been seen in other countries in Europe.
The Manchester and HPA teams reviewed 1,413 people who had listeria between 1999 and 2009. Pregnant women and their unborn or new-born children were not included in the study. Of these people, 936 – more than two-thirds – had one or more concurrent condition.
The research revealed that among those with concurrent conditions, people aged 60 years or over had a higher rate of listeria at 16.8 per million as compared to younger people whose rate was 4.6 per million.
Overall, the rate of listeria was 4.9 times higher for cancer patients than for patients with other concurrent conditions. Within the cancers the highest rate was among those with cancers of the blood – which was 17.6 times higher than for other conditions. Cancer was also the most common concurrent condition among cases of listeria, with a malignancy reported for a third of cases. Blood-borne cancers accounted for 41 per cent of the reported cancers.
In addition to cancer, diseases of the liver, kidney and connective tissue (for example Lupus), as well as alcoholism, diabetes, high blood pressure and inflammation of the intestines (for example Crohn’s disease) were also found to increase the risk of developing listeria.
Professor Sarah O’Brien, who is based in Manchester’s School of Translational Medicine, said: “Our work with the Health Protection Agency has shown that people receiving cancer treatment or who have conditions like diabetes, kidney or liver disease, are at much higher risk of listeria infection and so need good food-safety advice about preventing it.
“Certain foods, like prepacked or delicatessen sliced meats, soft cheeses, smoked fish, pates and unpasteurised milk, are known to increase the risk of listeria infection in vulnerable people. This research is a timely reminder to clinicians looking after people in these vulnerable groups to alert them to avoid high-risk foods and thereby reduce their risk of this serious illness.”