African swine fever in domestic pigs in Estonia 2015–2017: Epidemiological analysis of outbreaks

African swine fever (ASF) was first detected in Estonian wild boar population in September 2014. The first outbreaks in domestic pigs occurred in summer 2015. This paper summarises the results of epidemiological investigations of all 26 outbreaks that occurred during 2015 to 2017. On most of the affected farms, the first clinical signs were mild and not characteristic for ASF. The spread of the virus within farms has been slow and the contagiousness of the virus has been relatively low. Our findings suggests that virus introduction to the farms occurred via indirect transmission routes due to insufficient biosecurity. The presence of ASF virus in wild boar populations is the main factor facilitating infection of farms. All outbreaks occurred from June to September. The total herd incidence of outbreaks was similar across all three years, being 2.4% in 2015 and 2016, and 2.0% in 2017.