Modelling the spread of emerging infectious diseases in animal health: case study of lumpy skin disease in the Balkans, 2015–2016

The spatial and temporal study of the spread of emerging infectious diseases is crucial to understand their epidemiology and evaluate the risk of introduction into disease-free areas. In this paper, we present a generic method that models the spread rate of emerging infectious diseases that we applied to Lumpy Skin Disease (LSD), a current epizooty affecting cattle in the Balkans, from May 2015 to July 2016. In the study period, 824 outbreaks of LSD were reported in eight countries. Hotspots of viral transmission were identified mainly south of the Turkish/Greek border, southwest of Bulgaria and south of the Serbian/Bulgarian border. By using Thin Plate Spline Regression (TPSR) to interpolate the week of first invasion, we estimated the spread rate based on the mean duration of time for the infection to spread across a given area (1km). The median spread rate was 7.8km per week, with an interquartile interval of 4.6 to 13.7km and a maximum value reaching 375.6km. The distribution of spread rate indicates two diffusion processes: a localised diffusion covering small distances and suggesting vector transmission, and a diffusion at greater distances possibly due to anthropogenic movement of infected animals. Further research should focus on identifying environmental and socio-economic factors that might influence the spread of LSD to better understand the disease epidemiology and suggest targeted control measures.