Geographic and Seasonal Variation in Campylobacteriosis Open Access

Ailes, Elizabeth (2010)

Permanent URL: https://etd.library.emory.edu/concern/etds/cf95jc11f?locale=en
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Abstract

Campylobacter infections are a major cause of bacterial gastroenteritis in the U.S.,
where approximately 2 million people become ill annually. As campylobacteriosis is not
nationally notifiable and reporting requirements vary from state to state, laboratory-
based surveillance data from the Foodborne Diseases Active Surveillance Network
(FoodNet) is vital for assessing the magnitude of the disease burden and monitoring
trends of this important pathogen. Since FoodNet was established in 1996, regional and
seasonal variation in campylobacteriosis has been observed. In order to better
understand these patterns, the first goal of this dissertation was to examine key factors
that may explain the observed geographic variation in campylobacteriosis across the 10
FoodNet sites, such as geographic differences in surveillance artifacts (health care use,
stool sample submission, and clinical laboratory practices) or risk factors for
campylobacteriosis (high risk foods and other exposures). The second goal was to
examine whether climatic factors were associated with campylobacteriosis and whether
seasonal variation in risk factors existed. An analysis of multiple cross-sectional surveys
conducted in the FoodNet sites did not find evidence to suggest that differences in
healthcare utilization or stool sample submission practices explained the geographic
variation in campylobacteriosis. Similarly, analysis of a survey of clinical laboratories
found that variation in clinical laboratory methods is unlikely to account for the
geographic variation in campylobacteriosis. Additionally, an examination of case-
control study data showed no evidence of geographic effect modification of select risk
factors for campylobacteriosis, although the frequency of some exposures did vary by
FoodNet site. An analysis of surveillance and meteorological data showed a modest
association between campylobacteriosis and both minimum temperature and extreme
precipitation events. No evidence of seasonal effect modification of risk factors was
found. The goal of this dissertation was to examine key factors that may explain the
observed variation in campylobacteriosis, given the constraints of data collected for
public health surveillance purposes. Reasons for the geographic and seasonal variation
in campylobacteriosis in the FoodNet sites remain elusive. Potential areas of further
exploration include differences in the circulating strains of Campylobacter, the quantity
of Campylobacter on poultry, and immune response to Campylobacter.

Table of Contents

CHAPTER 1. INTRODUCTION 1
CHAPTER 2. BACKGROUND 3
Campylobacter Microbiology 3
Survival Mechanisms 5
Reservoirs 6
Animal Reservoirs 7
Environmental Reservoirs 8
Campylobacter on Food 10
Poultry 10
Milk 12
Drinking Water 13
Cross-contamination of Food 14
Clinical Features 14
Antibiotic Resistance 17
Immunity 18
Epidemiology of Campylobacter Infections 19
United States 20
Europe 21
Developing Countries 21
Risk and Protective Factors for Campylobacter Infection 22
Risk Factors 22
Protective Factors for Campylobacter Infection 26
Outbreaks 27
Surveillance in the United States 28
Clinical Laboratory Diagnostic Methods 29
Transport Media 30
Non-culture Methods 31
Culture Methods 31
American Society for Microbiology Guidelines 34
Prevention of Campylobacter Infections 35
Public Health Implications 37
Possible Explanations for Geographic Variation in Campylobacter Incidence 38
Surveillance Artifacts 39
True Differences in Incidence Rates 43
Seasonal Variation in Campylobacter Incidence 47
Seasonal Variation in Exposure to Campylobacter 47
Temperature-Dependence of Campylobacter Incidence 50
Summary 53
References 54
Tables and Figures 76
CHAPTER 3. DISSERTATION OBJECTIVES 78
CHAPTER 4: DO DIFFERENCES IN RISK FACTORS OR HEALTH CARE USE EXPLAIN THE GEOGRAPHIC VARIATION IN CAMPYLOBACTERIOSIS IN THE FOODNET SITES ? 79
Abstract 79
Introduction 79
Methods 81
FoodNet 81
Case-Control Study of Risk Factors for Campylobacteriosis 82
Differences in Risk Factors for Campylobacteriosis 83
Population Surveys of Diarrheal Disease and Healthcare Use 85
Differences in Health Care Utilization and Stool Sample Submission 86
Results 88
Differences in Risk Factors for Campylobacteriosis 88
Differences in Health Care Utilization and Stool Sample Submission 89
Discussion 89
References 96
Tables and Figures 100
CHAPTER 5: IS THERE GEOGRAPHIC VARIATION IN CLINICAL LABORATORY PRACTICES FOR THE DETECTION OF CAMPYLOBACTER IN THE FOODNET SITES? 105
Abstract 105
Introduction 105
Methods 107
FoodNet 107
Survey Data 107
Statistical Analysis 108
Results 111
Survey Data 111
Statistical Analysis 112
Discussion 113
References 118
Tables and Figures 121
Appendix 5A. Additional Analyses 128
Frequency of laboratory characteristics by FoodNet site 128
Laboratory profile analyses 130
Tables and Figures 132
Appendix 5B. Rationale for Use of Salmonella Data 135
Isolating the Impact of Laboratory Practices 135
Tables and Figures 138
CHAPTER 6: WHAT IS THE ASSOCIATION BETWEEN RAINFALL AND TEMPERATURE AND CAMPYLOBACTER INFECTIONS IN THE FOODNET SITES FROM 1996-2006? 141
Abstract 141
Introduction 141
Methods 143
Data Sources 143
Data Analysis 144
Results 148
Discussion 151
References 158
Tables and Figures 162
Appendix 6A:Distributed Lags 176
CHAPTER 7: DO DIFFERENCES IN RISK FACTORS EXPLAIN THE SEASONAL VARIATION IN CAMPYLOBACTERIOSIS? 179
Abstract 179
Introduction 179
Methods 180
Statistical Methods 182
Results 184
Discussion 185
References 190
Tables and Figures 192
CHAPTER 8: DISCUSSION 196
Conclusion 196
Future Directions 198
References 201

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