Modelling the transmission dynamics and the effect of different control strategies for African swine fever virus in East Africa

Abstract

African swine fever (ASF) is a highly contagious, lethal and economically devastating haemorrhagic disease of domestic pigs. Knowledge of the epidemiology of the disease is important for the design of improved control measures. Such insights of the dynamics of virus can be obtained from mathematical constructs. In this study, we used two methods to estimate the basic reproduction number (R0) from field data. Our estimates predicted persistence of ASF in pig populations and recommended enhanced biosecurity measures. We developed a stochastic model to assess the relative impact of the timing of the implementation of different control strategies on disease-related mortality. The results showed that intervention within 14 days of the outbreak and using a combination of strategies was the best control option. The modelling approach was particularly valuable in that it determined an optimal timing for implementation of interventions. A between-village spatial-deterministic model was developed. The model simulations showed that there were intervention windows of 30 days from the onset of the outbreak to reduce ASFV spread between villages. The study also analysed cross sectional data collected in a survey conducted in the study area to identify key parameters of low input production systems. We found out that farmers mostly kept local pig breeds by tethering. They fed the pigs on farm crop residues and household food leftovers or swill. We recommend timely intervention by authorities during outbreaks; the use of a cocktail of control strategies; restriction of free movement of animals; and improving the supply of affordable pig feeds to incentivize adoption of better husbandry and health practices and increasing pig productivity.