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Abstract :

Q fever, a worldwide zoonotic disease caused by Coxiella burnetii, is a looming concern for livestock and public health. Epidemiological features of inter-herd transmission of C. burnetii in cattle herds by wind and trade of cows are poorly understood. We developed a novel dynamic spatial model describing the inter-herd regional spread of the C. burnetii propagation in an enzootic region. Spread of C. burnetii between dairy herds of Finistère department, France was predicted and compared with observed spread of the infection. Our model predictions indicated that the majority of infections in disease-free herds occur due to windborne transmission. Infections acquired through this pathway are shown to cause relativity small and ephemeral intra-herd outbreaks. On the other hand, disease-free herd purchasing an infectious cow will experience significantly higher intra-herd prevalence. Results also indicated that, both transmission routes are independent from each other without any synergistic effect. Lastly, effects of implementation of vaccination on regional spread were assessed by comparing different strategies to select herds for vaccination. Vaccinating cows and heifers of 70% of herds using Phase I vaccine over 10 years resulted into significant reduction the prevalence of C. burnetii positive herds. Vaccinating already infected herds was found to be most effective strategy. Besides providing better understanding of C. burnetii infection dynamics at regional scale, this work also gives important insights to control the infection in animal populations.

Key words :

Coxiella burnetii, multiscale modelling, plume model, cattle movements, control, vaccination