Campylobacter spp. is an important causative agent of diarrheal illness worldwide. The disease is frequently associated with foodborne transmission, but other routes of exposure are increasingly recognized. A systematic review and meta-analysis of case-control studies were performed to determine the main risk factors associated with sporadic campylobacteriosis. Suitable scientific articles published up to March 2017 were identified through a systematic literature search and subject to methodological quality assessment. From each study, odds ratios (OR) as measures of association were extracted or calculated, as well as study characteristics such as study population, design, type of model used and risk factor categorization. Mixed-effects meta-analytical models were adjusted by population type to appropriate data partitions. From 4453 identified references, the quality assessment stage was passed by 71 case-control studies focusing on sporadic campylobacteriosis. The eligible studies were conducted between 1981 and 2012 and provided 1336 ORs for meta-analysis. The meta-analysis identified international travel (pooled OR=4.626), recent use of gastric antacids (pooled OR=2.911), occupational exposure to animals/carcasses (pooled OR=3.022), and food consumption (in particular raw or undercooked eggs, poultry, beef, and dairy) as the main risks factors for sporadic campylobacteriosis in the mixed population. In the child population, the main risk factors concerned environmental/animal transmission routes (e.g. drinking untreated water (pooled OR=3.261), exposure to recreational water (pooled OR=3.156), exposure to farm/rural environment (pooled OR=3.128), contact with farm animals (pooled OR=2.747), person-to-person transmission (pooled OR=2.736) and consumption of raw milk (pooled OR =2.603). The results of this meta-analysis highlight the importance of overlooked routes and vehicles of transmission (environment, animal contact, and other food vehicles) of Campylobacter that should be explored in dedicated studies.
