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Title: Redefining the population at risk of listeriosis in England and Wales
Author: Mook, Piers A. N.
ISNI:       0000 0004 2749 061X
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2012
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Listeriosis is a rare but severe food‐borne disease caused by the opportunistic, bacterial pathogen Listeria monocytogenes. The elderly, those who are immunocompromised and pregnant women and their unborn or newborn infants are disproportionately affected. Listeriosis has a high case fatality ratio (up to 44%) and is the commonest cause of death ascribed to a food‐borne pathogen in the United Kingdom (UK). The number of cases of listeriosis in England and Wales reported to the Health Protection Agency (HPA) ‐ the arms length governmental body mandated with protecting the health of the population ‐ increased from an average of 110 cases per year between 1990 and 2000 to an average of 192 cases per year between 2001 and 2009. The epidemiology of listeriosis appeared to change with the observed increase almost exclusively among non‐pregnancy related cases, aged ≥60 years presenting with bacteraemia in the absence of central nervous system infection (CNS). Given the potential severity of listeriosis and that, as a predominantly foodborne disease, these infections are largely avoidable, there was a public health imperative to investigate the observed increase. Disease presentation, concurrent conditions, medications, deprivation, diet and mortality risk factors amongst non‐pregnancy related listeriosis cases and ethnicity amongst pregnancy related cases were investigated using national surveillance data. The increased incidence of bacteraemic cases occurred in those with cancer, particularly digestive organ malignancies (Odds ratio (OR) [95% confidence interval (CI)]: 16.7 [3.8 – 73]) and, to a lesser degree, those with conditions that necessitate treatment with stomach acid inhibiting medication (3.2 [1.5 – 6.6]). Ethnicity and/or deprivation were found to be important drivers for infection. Compared to the most affluent areas, disease incidence was 38% (95% CI: 16 to 65) higher in the most deprived areas of the country. Cases were more likely than the general population to purchase foods from convenience stores (OR [95% CI]: 5.37 [3.53 – 8.17]) or from local services ‐ bakers (3.40 [2.39 – 4.86]), butchers (1.62 [1.11 – 2.34]), fishmongers (5.05 [3.19 – 7.99]) and greengrocers (1.92 [1.32 – 2.78]) ‐ and their risk profile changed with increasing deprivation. The proportion of pregnancy related cases classed as ethnic increased significantly from 2001 to 2008 (chi‐square test for trend; p=0.002). The increase in the proportion of pregnancy related cases that were ethnic was most marked in 2006, 2007 and 2008, when the incidence was higher than expected given the underlying population (Relative risk (RR) [95% CI]: 2.38 [1.07 – 5.29], 3.82 [1.82 – 8.03] and 4.33 [1.74 – 10.77], respectively). A wide range of underlying conditions appeared to increase the risk of infection, most notably diseases of the liver (RR [95% CI]: 22.4 [17.7 – 28.4]), systemic connective tissue disorders (18.3 [12.6 – 26.6]), neoplasms of the lymphoid, hematopioetic, and related tissues (17.6 [15.1 – 20.6]), psychoactive substance (alcohol related in 96% of reports; 12.3 [9.4 – 16.1]) and renal failure (12.2 [9.8 – 15.1]). Associated medications, including cytotoxic drugs (RR [95% CI]: 320.9 [228.5 – 450.7]), drugs affecting the immune response (18.5 [11.6 – 29.5]) and corticosteroids (11.1 [8.5 – 14.6]), and food groups, most notably smoked salmon (OR [95% CI]: 4.82 [2.99 – 7.76]), other cold cooked fish (22.32 [15.85 – 31.44]), camembert (4.80 [2.32 – 9.90]), hard cheese other than cheddar (2.37 [1.69 – 3.30]), blue cheese (2.24 [1.47 – 3.43]), also appeared to be associated with increased risk of infection. Underlying conditions, particularly malignancies of the breast (OR [95% CI]: 3.2 [1.7 – 6.2]) and respiratory and intrathoracic organs (3.9 [2.2 – 7.1]), alcoholism (2.7 [1.6 – 4.3]), cardiovascular diseases (1.4 [1.01 – 1.9]), treatment to reduce stomach acid secretion (1.6 [1.1 – 2.3])and increasing age (cases ≥80 years versus less than 60 years; 3.1 [2.3 – 4.2]) increased the risk of death amongst cases. This cohesive body of work redefines the population at risk of listeriosis and indicates that there is added value in actively targeting appropriate food safety advice at a range of vulnerable groups other than pregnant women, to whom information has previously been routinely and preferentially disseminated.
Supervisor: Not available Sponsor: Health Protection Agency (Great Britain) (HPA)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QR Microbiology ; RA0421 Public health. Hygiene. Preventive Medicine ; RC Internal medicine