A questionnaire survey for the assessment of wild-domestic pig interactions in a context oedema disease outbreaks among wild boars (Sus scrofa) in South-Eastern France

Pig outdoor farming is gaining popularity and commercial success in the European Union, and its expansion, together with an increasing wild boar population, facilitates interactions between domestic and wild suids. In the Southern French Department of Ardeche, several episodes of mass mortalities due to infection with an enteropathogenic strain of Escherichia coil causing oedema disease (OD) were reported in wild boar populations between 2013 and 2016. In order to investigate a potential link between those events and the frequency of interactions between wild boar and domestic pig, we analyzed regional vegetation and hunting bag data and implemented a semi-structured questionnaire survey among a total of 30 outdoor pig farmers and 30 hunters distributed inside and outside the identified area of OD emergence. One third of interviewed farmers (11/30) had experienced intrusions of wild boars in domestic pig premises during the previous year. Similarly, 23% of interviewed hunters reported interactions between wild boar and feral free-ranging pigs in recent years, and 60% reported the observation of free-ranging pigs with a phenotypic feature of Vietnamese pot-bellied pigs (55%). Our analysis identified that in the OD emergence area, several factors could facilitate the transmission of pathogens between wild and domestic suids including a predominance of forested vegetation, a higher estimated wild boar density, weaker levels of farm biosecurity, a higher level of reported wild boar intrusions in pig farms and several reports of feral pot-bellied pig presence. Although our sample was limited, our study suggested a widespread occurrence of situations facilitating the transmission of pathogens between wild and domestic suids. Similar studies in other rural regions in the European Union are recommended, in order to promote preparedness for the emergence and circulation of shared swine pathogens.