An ecological study of sociodemographic, agricultural and environmental factors associated with laboratory confirmed campylobacteriosis cases in Tennessee

Background Campylobacteriosis is one of the most reported enteric infections in the United States. Although individual risk factors are well described, ecological determinants such as private well water use and proximity to animal feeding operations remain understudied. This study assessed the relationship between sporadic campylobacteriosis and zip code–level ecological risk factors in Tennessee. Methods We analyzed 7,828 laboratory-confirmed, non-outbreak human campylobacteriosis cases reported to FoodNet in Tennessee from 2013 to 2022. Cases were aggregated by zip code and year to calculate annual incidence and merged with ecological data on animal operations, private well counts, population density, rurality, and sociodemographic characteristics. Bivariate and multivariate negative binomial regression models were used to identify significant associations. Results Annual incidence ranged from 9.80 per 100,000 in 2014 to 13.15 per 100,000 in 2022. Factors associated with increased incidence of campylobacteriosis in a zip code area were a year increase in the median age of a zip code (IRR = 1.0035; 95%CI: 1.0003—1.0077), rurality (IRR = 1.2668; 95% CI: 1.0862—1.4774), chicken operations in a zip code (IRR = 1.1529; 95% CI: 1.0377—1.2808) and higher in the prevalence of water wells in a zip code (IRR = 1.0073; 95% CI: 1.0039—1.0107). Increase in population density in a zip code was associated with a decrease incidence of campylobacteriosis (IRR = 0.9995; 95% CI: 0.9994—0.9997). Conclusions Chicken operations, private wells, and living in rural areas were associated with elevated campylobacteriosis incidence in Tennessee, highlighting the need to protect well water to reduce possible agricultural runoff exposure.