Source attribution of human campylobacteriosis using a meta-analysis of case-control studies of sporadic infections

Abstract

Campylobacter spp. is a widespread and important cause of human illness worldwide. Disease is frequently associated with foodborne transmission, but other routes of exposure, such as direct contact with live animals and person-to-person transmission, are also recognized. Identifying the most important sources of human disease is essential for prioritizing food safety interventions and setting public health goals. Numerous case-control studies of sporadic infections of campylobacteriosis have been published. These studies investigated a variety of potential risk factors for disease, often using different methodologies and settings. Systematic reviews (SRs) consist of a formal process for literature review focused on a specific research question, and include the identification of relevant literature, quality assessment of relevant studies, summarization or statistical analysis of data, and conclusions. With the objective of identifying the most important risk factors for human sporadic campylobacteriosis, we performed a SR of case-control studies of human sporadic cases and a meta-analysis of the obtained results. A combined SR focusing on Salmonella and Campylobacter studies was performed and the results analysed separately. From 1295 identified references, 131 passed the relevance screening, 73 passed the quality assessment stage, and data was extracted from 72 studies. Of these, 38 focused on campylobacteriosis. Information on exposures of cases and controls, and estimated odds ratios for investigated risk factors were collected and analysed. In the meta-analysis, heterogeneity between the studies and possible sources of bias were investigated, and pooled odds ratios for identified risk factors were estimated. Results suggest that travelling abroad, eating undercooked chicken, environmental sources, and direct contact with farm animals were significant risk factors for campylobacteriosis. Sub-analyses by geographical region, age group, and study period were performed, and differences were discussed.

Risk Factors for Campylobacteriosis in Two Washington State Counties with High Numbers of Dairy Farms

“…Additional exposures significantly associated with disease in this study were contact with a sick pet ( Table 2) and contact with live poultry (Table 3), suggesting that live animal contact is an important source of exposure to Campylobacter. The finding that pet ownership and contact with sick pets are risk factors for campylobacteriosis is consistent with previous epidemiological studies that reported contacts with pets, particularly puppies and kittens with diarrhea, as significant risk factors (10,(26)(27)(28). In Yakima County, living or working on a nondairy farm and having contact with live poultry were both associated with disease and with etiological fractions of 13 to 14%, although the confidence limits surrounding the latter did not exclude 0.…”

Determining Risk Factors of a Non-Point Source Outbreak of Campylobacter Cases Using Case-Case and Case-Control Studies

“…While the recruitment goal was a 2:1 match of controls to cases, this did not occur in all the age groups, particularly among boys (age [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. This group represented 33% of all cases reported from outbreak cases but only 13% of the phone controls.…”

“…In the United States 45,000 laboratory confirmed cases are reported each year [11], but are estimated to cause 2.4 million cases annually [12]. Most of these cases are sporadic in nature [13][14][15][16][17][18][19], however, for outbreaks that do occur, most are linked to unpasteurized dairy [20,21] and untreated water [22]. While these studies help to determine the associated risk factors for the disease, they are costly and time consuming.…”

Climate change and primary industries

“…A number of studies have identified drinking water, especially undisinfected drinking water, and food items such as poultry meat as sources of campylobacteriosis (Domingues et al 2012, Ethelberg et al 2005, Kapperud et al 2003, Kapperud et al 1992. The European Food Safety Authority (2010) reported that 20-30% of the human cases may be the direct result of handling and consumption of broiler meat, whereas 50-80% may be indirectly associated with broilers acting as a reservoir of the pathogen.…”