Epidemiological Characterization of African Swine Fever Dynamics in Ukraine, 2012-2023

Abstract

African swine fever (ASF) is a viral disease, endemic to Africa, that causes high mortality when introduced into domestic pig populations. Since the emergence of p72-genotype II African swine fever virus (ASFV) in Georgia in 2007, an ASF epidemic has been spreading across Europe and many countries in Asia. The epidemic first reached Ukraine in 2012. To better understand the dynamics of spread of ASF in Ukraine, we analyzed spatial and temporal outbreak data reported in Ukraine between 2012 and mid-2023. The highest numbers of outbreaks were reported in 2017 (N = 163) and 2018 (N = 145), with overall peak numbers of ASF outbreaks reported in August (domestic pigs) and January (wild boars). While cases were reported from most of Ukraine, we found a directional spread from the eastern and northern borders towards the western and southern regions of Ukraine. Many of the early outbreaks (before 2016) were adjacent to the border, which is again true for more recent outbreaks in wild boar, but not for recent outbreaks in domestic pigs. Outbreaks prior to 2016 also occurred predominantly in areas with a below average domestic pig density. This new analysis suggests that wild boars may have played an important role in the introduction and early spread of ASF in Ukraine. However, in later years, the dynamic suggests human activity as the predominant driver of spread and a separation of ASF epizootics between domestic pigs and in wild boars. The decline in outbreaks since 2019 suggests that the implemented mitigation strategies are effective, even though long-term control or eradication remain challenging and will require continued intensive surveillance of ASF outbreak patterns.

Keywords: ASF; ASFV; African swine fever; African swine fever virus; One Health; Ukraine; backyard farms; epidemiology; outbreak; wild boar.

Figure 1

Number of reported ASF cases in Ukraine, depicted on a cumulative monthly basis (dark blue dots) and on a yearly basis (light blue bars) from January 2014 through May 2023.

Figure 2

Reported outbreaks by month (cumulative number across all years) broken down by southern (Kherson, Odesa, Mykolaiv; orange bars) and northern (all other; blue bars) oblasts (excluding Crimea); panel (A) showing domestic pig and panel (B) wild boar outbreaks.

Figure 3

Series of hotspot maps, with colors trending towards red indicating high and trending towards blue low ASF outbreak activity. Panel (A) based on all reported cases from 2012 through May 2023; panels (B–D) by season (April–March) for the years with the highest numbers of ASF outbreaks 2016/2017 (B), 2017/2018 (C) and 2018/2019 (D).

Figure 4

Epidemiological clustering of ASF outbreaks in Ukraine, 2012–2018 (numbered chronologically) according to the “biology and behavioral model”. Ellipses refer to one standard deviation around the mean geographic center of outbreaks.

Figure 5

Graph depicting the average distance and standard deviation of outbreaks from official borders or the north of Crimea oblast by season (April–March) for domestic pigs (red) and wild boars (green).

Figure 6

Graph showing the average forest density (circles with a radius of 25 km) around outbreak sites by season (April–March) for domestic pigs (red) and wild boars (green).

Figure 7

Graph showing the correlation between outbreaks in domestic pigs (red) and wild boars (green) with the modelled population density of domestic pigs in Ukraine in the surrounding area (circles with 25 km radius). Data by season (April–March) and displayed in % of average pig density in Ukraine with standard deviations.