Risk Factors for Campylobacteriosis in Australia: Outcomes of a 2018–2019 Case-Control Study

Abstract

Background We aimed to identify risk factors for sporadic campylobacteriosis in Australia, and to compare these for Campylobacter jejuni and Campylobacter coli infections. Methods In a multi-jurisdictional case-control study, we recruited culture-confirmed cases of campylobacteriosis reported to state and territory health departments from February 2018 through October 2019. We recruited controls from notified influenza cases in the previous 12 months that were frequency matched to cases by age group, sex, and location. Campylobacter isolates were confirmed to species level by public health laboratories using molecular methods. We conducted backward stepwise multivariable logistic regression to identify significant risk factors. Results We recruited 571 cases of campylobacteriosis (422 C. jejuni and 84 C. coli) and 586 controls. Important risk factors for campylobacteriosis included eating undercooked chicken (adjusted odds ratio [aOR] 70, 95% CI 13–1296) or cooked chicken (aOR 1.7, 95% CI 1.1–2.8), owning a pet dog aged < 6 months (aOR 6.4, 95% CI 3.4–12), and the regular use of proton-pump inhibitors in the four weeks prior to illness (aOR 2.8, 95% CI 1.9–4.3). Risk factors remained similar when analysed specifically for C. jejuni infection. Unique risks for C. coli infection included eating chicken pâté (aOR 6.1, 95% CI 1.5–25) and delicatessen meats (aOR 1.8, 95% CI 1.0–3.3). Eating any chicken carried a high population attributable fraction for campylobacteriosis of 42% (95% CI 13–68), while the attributable fraction for proton-pump inhibitors was 13% (95% CI 8.3–18) and owning a pet dog aged < 6 months was 9.6% (95% CI 6.5–13). The population attributable fractions for these variables were similar when analysed by campylobacter species. Eating delicatessen meats was attributed to 31% (95% CI 0.0–54) of cases for C. coli and eating chicken pâté was attributed to 6.0% (95% CI 0.0–11). Conclusions The main risk factor for campylobacteriosis in Australia is consumption of chicken meat. However, contact with young pet dogs may also be an important source of infection. Proton-pump inhibitors are likely to increase vulnerability to infection.

Source attribution of campylobacteriosis in Australia, 2017–2019

“…However, as most campylobacteriosis in Australia is believed to be foodborne (Vally et al., 2014 ), we can approximate the risk posed by the consumption of meat from a source with the relative attributable proportion, that is, by dividing the proportion of cases attributed to that source by its domestic consumption. Applying this method, we estimate consuming chicken meat posed a 22–27 times greater risk of campylobacteriosis than consuming meat from pigs and ruminants, in accord with the findings of the case–control study (Cribb et al., 2022 ).…”

“…Study data were collected as part of the broader CampySource project, a collaboration between Australian academic institutions, government agencies, and industries. A detailed description of study methods and data collection can be found elsewhere (Cribb et al., 2022 ; Varrone et al., 2018 ; Walker et al., 2019 ; Wallace et al., 2021 , 2020 ). The sequence readset for each food isolate (Bioproject Accession: PRJNA591966), case isolates sampled as part of the case–control study (Bioproject Accession: PRJNA592186), and the case isolates included in the national snapshot (Bioproject Accession: PRJNA560409) are available through GenBank (Clark et al., 2016 ).…”

“…Cases were enrolled as part of a case–control study and a national snapshot of campylobacteriosis for which detailed sampling methods have been described previously (Cribb et al., 2022 ; Varrone et al., 2018 ; Wallace et al., 2021 ). We defined a case as a person with acute diarrhea where Campylobacter spp.…”