Spatial, temporal, and occupational risks of Q fever infection in South Australia, 2007-2017

The burden of Q fever on at risk population groups in Australia is substantial, despite the availability of a vaccine. Our objectives were to: (a) describe the epidemiology of notified Q fever cases in South Australia (SA), (b) identify if Q fever infection is associated with occupational exposure, and (c) detect the possible spatial and temporal association of Q fever with livestock density.

Laboratory confirmed Q fever notifications from January 2007 to December 2017 were obtained from the SA Health Department. Q fever notification rates and incidence rate ratios were calculated for gender, notification year, age group, occupation category, and primary exposure suburb. Spatial mapping and analysis of Q fever notifications was undertaken using livestock data, and abattoirs and saleyards located in SA.

During the study period 167 Q fever cases were notified. Males predominated (72%), with higher rates observed in the 21-40year age group (1.52/100,000), and eight cases (5%) reported prior Q fever vaccination. Most frequently listed occupation categories were livestock farmers (35%), and abattoir workers (20%), but in 15% of cases, there was no known occupational risk. Highest notifications (22%) were recorded in the suburb containing an abattoir. The number of goats, cattle and sheep was not associated with Q fever notifications.

Q fever predominance among males in their twenties and thirties may indicate vaccination under-coverage among the young workforce possibly due to high turnover of workers. Q fever among those vaccinated raises concerns about vaccine efficacy or potential waning immunity. Our findings are consistent with previous studies highlighting abattoir workers as a high-risk occupational group because of its transient workforce, and low vaccination coverage. Q fever notifications in SA may be unrelated with spatial livestock density. Further One Health research involving veterinary, public health and environmental data is required.