Examining the epidemiology of campylobacteriosis in Australia.
Creators: name: Moffatt, Cameron
Publisher: name: The Australian National University
Year: 2021

description: Introduction. Campylobacter causes considerable disease burden in Australia but a focused examination of its epidemiology has been lacking. Disease incidence, outbreak potential and outcomes like hospitalisation are key features of Campylobacter's epidemiology, informing prevention and control efforts. Methods. Incidence. The aim was to describe incidence trends from 1998-2003 using national surveillance data. Negative binomial regression was used to estimate incidence rate ratios (IRRs) for sex, season, state and trend over time by age-group. Outbreaks. The aim was to describe the epidemiology of outbreaks using national data. Analyses were descriptive, examining outbreak features including transmission routes and evidence levels. An additional outbreak study incorporating whole genome sequencing is included. Hospitalisation. Aims included quantifying Campylobacter admissions, describing clinical characteristics and examining factors associated with inpatient care. Australian Capital Territory (ACT) public hospital administrative and laboratory datasets for 2004-2003 were obtained. Sensitivity of morbidity coding was calculated to assess underreporting. Clinical characteristics were examined via descriptive statistics. Factors associated with blood culture, bacteraemia, antibiotic use and isolate non-susceptibility were assessed via logistic regression. Results. Incidence. The study included 245,023 Campylobacter cases. Male incidence was higher (IRR 1.20, 95% confidence interval (CI) 1.18-1.21) with a distinct seasonality demonstrated in spring (IRR 1.18, 95%CI 1.16-1.20). Age specific incidence showed falls in those &lt;40 yrs and rises for older persons, notably those &gt;70 yrs (IRR 1.75, 95%CI 1.63-1.88). Outbreaks. From 2001-2016, 84 Campylobacter outbreaks were identified, or 2.4% (51/2083) of all foodborne outbreaks. No increases over time occurred but the proportion of foodborne outbreaks due to poultry liver increased (p=0.04). Aged care was the most common setting with 26% (22/84) of outbreaks and 24% (252/1042) of cases, including 17 hospitalisations and 3 deaths. Transmission routes were unknown for 27% (23/84) of outbreaks, including 10 in aged care. Hospitalisation. There were 685 hospitalisations, with an ACT hospitalisation rate of 13.6%. Morbidity coding sensitivity was 52.8% (95% CI, 48.9-56.7%). Admitted cases (M=38.4 years) were older than community cases (M=31.0, p&lt;0.001). Age specific admission rates were higher in females, increasing for both sexes at 60 yrs. Comorbidities were present in 35% (237/685) of admissions. These cases were older and more likely to have dehydration, hypotension or renal impairment (all p&lt;0.001). Bacteraemia and kidney injury occurred in 4.1% (28/685) and 3.6% (23/685) of admissions. Inpatient mortality was 0.15%. Bacteraemia incidence was 0.71 cases per 100,000 population. Bacteraemia was associated with liver disease (adjusted Odds Ratio (aOR) 48.89, 95%CI 7.03-340.22, p&lt;0.001), Haematology admission (aOR 14.67, 95%CI 2.99-72.07, p=0.001) and age 70-79 yrs (aOR 4.93, 95%CI 1.57-15.49, p&lt;0.01). Antibiotics were given to 32% (219/685) of admissions, with treatment increasing over time (p&lt;0.05). Treatment was associated with Gastroenterology admission (aOR 3.75, 95%CI 1.95-7.20, p&lt;0.001), blood culture (aOR 2.76, 95%CI 1.79-4.26, p&lt;0.001) and age 40-49 yrs (aOR 2.34, 95%CI 1.14-4.79, p=0.02). Isolate non-susceptibility increased over time (p=0.01) and was associated with overseas travel (aOR 11.80 95%CI 3.18-43.83, p&lt;0.001). Conclusion. Australia experiences high rates of campylobacteriosis, with increasing incidence predicted among older age-groups. Despite high incidence outbreaks occur infrequently but hospitalisations are underestimated. Further work is needed to understand risk, including analysis of age and comorbidities as outcome predictors. Campylobacter causes significant public health and clinical burden, with disease risk and poor outcomes higher among older Australians.