Risk factors for African swine fever incursion in Romanian domestic farms during 2019

A Boklund,Y Van Der Stede,A Stegeman,H Roberts,C Gortázar,S Mortensen,H H Thulke,L C Gonzalez Villeta,J C Abrahantes,A Viltrop,A Bøtner,A Gogin,S Dhollander,K Ståhl,T Chesnoiu Vasile,A Papanikolaou,S J More

doi:10.1038/s41598-020-66381-3

Abstract

African swine fever (ASF) entered Georgia in 2007 and the EU in 2014. In the EU, the virus primarily spread in wild boar (Sus scrofa) in the period from 2014–2018. However, from the summer 2018, numerous domestic pig farms in Romania were affected by ASF. In contrast to the existing knowledge on ASF transmission routes, the understanding of risk factors and the importance of different transmission routes is still limited. In the period from May to September 2019, 655 Romanian pig farms were included in a matched case-control study investigating possible risk factors for ASF incursion in commercial and backyard pig farms. The results showed that close proximity to outbreaks in domestic farms was a risk factor in commercial as well as backyard farms. Furthermore, in backyard farms, herd size, wild boar abundance around the farm, number of domestic outbreaks within 2 km around farms, short distance to wild boar cases and visits of professionals working on farms were statistically significant risk factors. Additionally, growing crops around the farm, which could potentially attract wild boar, and feeding forage from ASF affected areas to the pigs were risk factors for ASF incursion in backyard farms.

Highlights

African swine fever (ASF) entered Georgia in 2007 and the EU in 2014
The results showed that close proximity to outbreaks in domestic farms was a risk factor in commercial as well as backyard farms
In backyard farms, herd size, wild boar abundance around the farm, number of domestic outbreaks within 2 km around farms, short distance to wild boar cases and visits of professionals working on farms were statistically significant risk factors

Summary

Introduction

African swine fever (ASF) entered Georgia in 2007 and the EU in 2014. In the EU, the virus primarily spread in wild boar (Sus scrofa) in the period from 2014–2018. Growing crops around the farm, which could potentially attract wild boar, and feeding forage from ASF affected areas to the pigs were risk factors for ASF incursion in backyard farms. Olesen et al described potential routes for indirect transmission of ASFV as uncooked pig meat, processed pig-derived products, feed, matrices contaminated with ASFV and blood-feeding invertebrates[3] Often these assessments were based on relatively small numbers of outbreak investigations, due to the small numbers of affected pig farms in each country. The source of spread to secondary cases were often unknown In those cases where the source of infection was clear, each of the following was implicated: contaminated vehicles, direct contact with pigs or people from pig farms, or introduction of pigs in the period close to outbreak detection[1]

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