Spatiotemporal clustering and Random Forest models to identify risk factors of African swine fever outbreak in Romania in 2018–2019

Abstract

African swine fever (ASF) has affected Romania since July 2017, with considerable economic and social consequences, despite the implementation of control measures mainly based on stamping out of infected pig populations. On the basis of the 2973 cumulative recorded cases up to September 2019 among wild boars and domestic pigs, analysis of the epidemiological characteristics could help to identify the factors favoring the persistence and spread of ASF. A statistical framework, based on a random forest methodology, was therefore developed to assess the spatiotemporal features of the epidemics and their relationships with environmental, human, and agricultural factors. The landscape of Romania was associated with the infection dynamics, particularly concerning forested and wetland areas. Waterways were also identified as a pivotal factor, raising questions about possible waterborne transmission since these waterways are often used as a water supply for backyard holdings. However, human activity was clearly identified as the main risk factor for the spread of ASF. Although the situation in Romania cannot be directly transposed to intensive pig farming countries, the findings of this study highlight the need for strict biosecurity measures on farms, and during transportation, to avoid ASF transmission at large geographic and temporal scales.

Key risk factors and impact of African swine fever spreading on pig production in Serbia

“…According to the experience from the Baltic region, contamination with wild boar carcasses can frequently keep the virus alive in the local area around villages or pig farms [25][26][27]. On the other hand, inadequate or low level of biosecurity in small holdings and backyards is often mentioned [21,24,25] as a potential risk factor that could play a role in ASF spreading in the domestic pig population [41,42]. Considering the infected territories in Southeast Europe, swill feeding, the presence of free-ranging pigs and home slaughtering, presence of a substantial number of smallholders were found as signifi cant indicators for ASF spreading in the domestic pig production sector [24,30,41].…”

“…In Southeastern Europe, the existence of a highly variable domestic pig farming system was previously reported [2,14,24]. Indeed, the main important difference comparing the EU member countries is related to the structure organisation of the domestic pig production sector.…”

“…The pig production sector in Southeast Europe is quite different and cannot be transposed to intensive pig farming EU countries [15,17]. Also, in the fi rst ASF infected country (Georgia), similar fi ndings were recorded, where farming practices vary considerably from region to region [15,24,30].…”

“…A large number of virus serotypes are known, but to date only serotype 2 has been identifi ed in Eurasia (serotype 1 is present only in Sardinia) [20,22]. The virus, of genotype 2, is highly virulent with a case-fatality rate higher than 95% in domestic pigs and wild boars [17,24,25]. While in wild African suids ASF infection runs a subclinical or asymptomatic course, in domestic pigs and Eurasian wild boars this is acute and peracute severe hemorrhagic disease [5,11].…”

Basic reproduction number of African swine fever in wild boars (Sus scrofa) and its spatiotemporal heterogeneity in South Korea

“…The African swine fever virus (ASFV) induced African swine fever (ASF) is a catastrophic hemorrhagic fever disease affecting wild boar ( Sus scrofa ) and domestic pigs, and having a tremendously detrimental impact on the pig industry in Africa, Europe, and Asia [ 1 ]. Since the ASFV can spillover from wild boar to domestic pigs, this livestock-wildlife interaction has been highlighted and is considered one of the targets for formulating control policies of ASF [ 2 3 ]. It is important to study and understand the disease dynamics in wild boar [ 4 5 6 ].…”