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Similarly those who reported an increasing daily consumption of unboiled tap water were more likely to present with diarrhoea and vomiting. Eating salads, cheese and fish/shellfish was reported less commonly by cases reporting vomiting and/or bloody diarrhoea, and few associations with infecting C. jejuni serotype were observed. This study suggests that for Campylobacter infection, vomiting and bloody diarrhoea share a similar aetiology, represent the more severe end of the disease spectrum and might relate to host susceptibility and/or infective dose. These findings have important implications for case-control studies of laboratory-confirmed Campylobacter infection. If heavily contaminated (“high dose”) foods lead to severe disease then it follows that „normal‟ doses will lead to „normal‟ disease, „lower‟ doses will lead to mild symptoms that might be dismissed as disease and the lowest doses will lead to sub-clinical infections. Some people will not be exposed at all (figure 5, below). Figure 5. An extension of the dose response model for Campylobacter infection and its hypothesised effect of case and control classification in case-control studies. 53
Cases in case-control studies of laboratory-confirmed infection will therefore consist of normal and severe infection (normal and high dose) whilst healthy controls will comprise individuals with very mild clinical (lower dose) or sub- clinical (lowest dose) infections and those who were not exposed (no dose). Thus, case-control studies might be biased towards detecting high-dose foods. An accurate assessment of the epidemiology of Campylobacter infection can therefore only be achieved whilst controlling for previous exposure to campylobacters in the control population. 7.8 Demographic determinants for Campylobacter infection in England & Wales. In the final year of the study (May 2002 to April 2003), data from the 2001 UK census became available. This provided an opportunity to address some of the methodological limitations experienced previously (paper 5 (Campylobacter Sentinel Surveillance Scheme Collaborators, 2003a)), and to examine in detail the role of other demographic determinants in Campylobacter infection in England and Wales (paper 8 (Gillespie et al., 2008)). Cases who reported no history of foreign travel in the two weeks preceding their illness were studied (N=15,907). Cases‟ descriptions of their ethnic origins and occupations were classified according to the UK census classification and Standard Occupational Classification (SOC) 2000 classification respectively. Overall, incidence was highest in infants, decreased from two to thirteen years, increased from 14 to 22 years and remained relatively stable from 22 to 69 years before declining from 70 years. This pattern varied with gender. Incidence was higher in males than females from birth to 17 years and this difference was most noticeable between 13 and 15 years. Gender-specific incidence then switched, with females at greater risk from 20 to 36 years. Greater variability was observed further up the age spectrum although overall, incidence was higher in males. Analysis by ethnic group confirmed and extended earlier findings, demonstrating that the increased incidence in resident Pakistanis was not an artefact of dated denominator data, and that 54
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Population-Based Sentinel Surveilla
Page 3 and 4: The research carried out by the can
Page 5 and 6: Dedication. This thesis is dedicate
Page 7 and 8: 7. Results (the published work). ..
Page 9 and 10: Statement identifying the degree fo
Page 11 and 12: Paper Reference Page 6 Gillespie IA
Page 13 and 14: Statement of the candidate’s cont
Page 15 and 16: Declaration form. I, Iain Andrew Gi
Page 17 and 18: 2. History. In contrast to other co
Page 19 and 20: The application of veterinary techn
Page 21 and 22: The incidence of laboratory-confirm
Page 23 and 24: were elderly or had a pre-existing
Page 25 and 26: they would for other bacterial gast
Page 27 and 28: papers (Pearson et al., 1977; Bruce
Page 29 and 30: Studies were most frequently conduc
Page 31 and 32: The content of peer-reviewed public
Page 33 and 34: infection. An approximation of the
Page 35 and 36: hypotheses a „blank canvas‟ app
Page 37 and 38: 6. Materials and methods. Regional
Page 39 and 40: presentation and severity, foreign
Page 41 and 42: together, etc). The results of the
Page 43 and 44: and improve response during the stu
Page 45 and 46: The published work. 7.1 Epidemiolog
Page 47 and 48: community illness was more common a
Page 49 and 50: north west England and in Yorkshire
Page 51 and 52: community was no different from oth
Page 53: provide useful insights into the ep
Page 57 and 58: 8. Discussion. The research carried
Page 59 and 60: The sentinel health authorities wer
Page 61 and 62: fundamentally flawed. Since the app
Page 63 and 64: control studies. The potential role
Page 65 and 66: Campylobacter spp. from cattle farm
Page 67 and 68: Cameron, S., Ried, K., Worsley, A.,
Page 69 and 70: Doyle, L. P. 1948, "The etiology of
Page 71 and 72: other industrialised countries," in
Page 73 and 74: Hanel, C. M. & Atanassova, V. 2007,
Page 75 and 76: Hudson, S. J., Lightfoot, N. F., Co
Page 77 and 78: Kessel, A. S., Gillespie, I., O'Bri
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Page 81 and 82: Department of Health and Human Serv
Page 83 and 84: Potter, R. C., Kaneene, J. B., & Ha
Page 85 and 86: Siemer, B. L., Harrington, C. S., N
Page 87 and 88: Sopwith, W., Birtles, A., Matthews,
Page 89 and 90: Campylobacter infection: a general
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Table A1.1: Notable events in the h
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Year Human medicine Veterinary medi
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Levy, A. J. 1928, "A gastro-enterit
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Appendix 2. An assessment of the ro
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compare the period after 2000 with
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condition was significantly associa
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Deaths/100,000 cases 600 500 400 30
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Table A2.1: Factors affecting the u
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Appendix 3. An analytical review of
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to indigenously acquired infection
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susceptibility to Campylobacter inf
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year demonstrated that only the num
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Table A3.1 Reported epidemiological
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Table A3.3 Selected reported risk f
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Table A3.5. The effect of various r
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Deming, M. S., Tauxe, R. V., Blake,
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Harris, N. V., Weiss, N. S., & Nola
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Kist, M. & Rossner, R. 1985a, in Ca
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Oosterom, J., den Uyl, C. H., Banff
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Severin, W. P. J. 1982, "Epidemiolo
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Appendix 4. The Campylobacter Senti
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