Aujeszky’s Disease and Hepatitis E Viruses Transmission between Domestic Pigs and Wild Boars in Corsica: Evaluating the Importance of Wild/Domestic Interactions and the Efficacy of Management Measures

Abstract

Wildlife species as reservoirs of infectious pathogens represent a serious constraint in the implementation of disease management strategies. In the Mediterranean island of Corsica, the dynamics of hepatitis E virus (HEV) and Aujeszky’s disease virus (ADV) are suspected to be influenced by interactions between wild and domestic pigs. To improve our understanding of these influences, we first compared the seroprevalences of both viruses in domestic pig populations from different locations with contrasted levels of wild–domestic interactions, ADV vaccination, biosafety, and farm husbandry. Second, we performed an analysis at a more restricted geographical scale, to assess the matching of ADV or HEV prevalence between sympatric wild boar and outdoor pig farms most exposed to interactions with wildlife. Logistic models were adjusted to the observed data. A high seroprevalence of HEV (>80%) and ADV (40%) in pigs, with no significant difference according to the region, confirms that both pathogens are enzootic in Corsica. Vaccination against ADV had a strong protective effect, even when performed voluntarily by farmers. Farm biosafety had an additional effect on pigs’ exposure, suggesting that contact between wild boars and pigs were involved in disease transmission. A strong correlation in HEV seroprevalence was observed between pigs and wild boars that were in close contact, and significantly lower seroprevalence was observed in pigs when they had little contact with wild boars due to spatial segregation. These results suggest a regular HEV circulation between sympatric wild boar and domestic pigs. The high HEV seroprevalence observed in domestic pigs (>80%) suggests a spillover of the virus from domestic to wild populations through environmental contamination, but this hypothesis has to be confirmed. Conversely, even though avoiding sows’ release on pasture during estrus showed some protecting effect in the free ranging pig farms regarding ADV, ADV seroprevalence was not dependent on the swine populations (wild or domestic) or on the wild–domestic spatial overlap, suggesting two quasi-separate enzootic cycles. This information will prove useful for designing more efficient disease management strategies in Corsica and similar contexts.

FaecalEscherichia colias biological indicator of spatial interaction between domestic pigs and wild boar (Sus scrofa) in Corsica

“…Concurrently, the agricultural decline and abandonment of agricultural land in recent decades have led to a notable increase in wild boar populations as evidenced by the approximately 30,000 wild boars hunted annually (ONCFS, ). Similar to other Mediterranean locations, these conditions provide an ideal environment for the interaction between wild and domestic pig populations (Jori, Relun et al., ) and the subsequent maintenance and transmission of pathogens detrimental for both the pig industry (Albina et al., ; Mur et al., ) and human health (Charrier et al., ; Pavio et al., ; Richomme, Boschiroli, Hars, Casabianca, & Ducrot, ). Previous work developed to collect information on interactions between wild and domestic pigs among farmers and hunters indicated a high incidence of direct contacts in extensive pig farms.…”

Drastic decline of hepatitis E virus detection in domestic pigs after the age of 6 months, Corsica, France

“…In Corsica, traditional extensive (or semi‐extensive) outdoor pig farming system is common. This kind of farming facilitates contact with wild boar populations sharing pathogens such as HEV (Charrier et al, ; Jori et al, ). Only 10% of Corsican pork products come from this traditional sector.…”

“…Two major studies on HEV have already been carried out on domestic pigs in Corsica. These were seroprevalence studies and anti‐HEV IgG has been detected in domestic and wild boar populations (Charrier et al, ; Jori et al, ). The higher seroprevalence observed in Corsican domestic pigs (88%), compared with Corsican wild boars (29%) suggests a spillover of HEV from domestic pigs to wild boars (Charrier et al, ; Jori et al, ).…”

“…These were seroprevalence studies and anti‐HEV IgG has been detected in domestic and wild boar populations (Charrier et al, ; Jori et al, ). The higher seroprevalence observed in Corsican domestic pigs (88%), compared with Corsican wild boars (29%) suggests a spillover of HEV from domestic pigs to wild boars (Charrier et al, ; Jori et al, ). HEV RNA was detected in two of the 24 pig samples tested (22 liver and 2 bile specimens); however, the number of tested samples was too small to estimate HEV infection rate (Jori et al, ).…”

Genetic Diversity among Pseudorabies Viruses Isolated from Dogs in France from 2006 to 2018

“…However, serological surveys indicated that PRV was still circulating in wild boars, with prevalence levels reaching 20-50% in regions with the highest population density [16,17], especially in the north-east and center of mainland France, as well as in Corsica [17][18][19]. The risk of such endemic PR in wild boars lies in reintroducing PRV into pig herds, especially those on outdoor farms due to potential contact between domestic pigs and wild boars [20]. Indeed, since the end of the eradication program in the pig industry, three PR outbreaks were detected through serological analyses in open-air pig farms in 2010, 2018, and 2019 [21][22][23].…”