Coxiella burnetii is the bacterium that causes Q fever in humans, with ruminants being key reservoirs. This bacterium was discovered in independent studies in the 1930s from sick abattoir workers in Queensland, Australia, and ticks in Montana, United States of America. While some models have investigated transmission in small-scale cattle and goat herds in Europe, gaps remain in the understanding of C. burnetii transmission in large-scale cattle production systems. This study aimed to quantify the transmission dynamics and parameters responsible for the persistence of C. burnetii in a dairy cattle herd, with a focus study on Australian strains and herd management practices. 

A novel, agent-based, stochastic, discrete-time simulation model was developed to simulate within-herd transmission of C. burnetii in an Australian cattle herd. The model incorporated herd demographics, reproduction, animal movements and individual-level variation in C. burnetii shedding. Transmission of infection was modelled with an SEIR (Susceptible-Exposed-Infectious-Recovered) structure with initial parameters drawn from available literature. Parameter fitting was conducted to recover observed apparent prevalence data across different parity groups at different time points. Sensitivity analyses identified the most influential parameters. These results can guide further studies and decisions around recommended control measures which include vaccination, environmental cleaning, isolation of infectious animals, breeding ban, and culling to help decrease public health risks.