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.

François Charrier,Ferran Jori,Oscar Maestrini,François Casabianca,Nicole Pavio,Johan Jouve,Sophie Rossi,Marie-Frédérique Le Potier,Céline Richomme,Christian Ducrot

doi:10.3389/fvets.2018.00001

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.

Highlights

CONTEXT: TWOPOPULATIONS, TWO PATHOGENS, AND MULTIPLE STORIESInteractions between wild and domestic animals can play a role in the maintenance of pathogens and thereby compromise the efficiency of disease control strategies [1,2,3]
The vaccination treatment was negatively correlated to Aujeszky’s disease virus (ADV) prevalence: a lower seroprevalence was observed in farms that implemented a self-vaccination process (ORno vaccination/self-vaccination = 3.88, 95% confidence intervals (CIs) [1.30; 11.57]), but this protective effect was much higher in farms that had implemented the official vaccination plan (ORself-vaccination/official = 3.39, 95% CI [1.07; 10.75])
Traditional free ranging farms exhibited a higher seroprevalence compared with the closed ones (ORfree ranging/close = 6.14, 95% CI [1.11; 34.12]); the absence of ADV seropositive individual in fenced pasture farms in our sample could not allow the comparison of that particular category to other biosafety levels

Summary

Introduction

CONTEXT: TWOPOPULATIONS, TWO PATHOGENS, AND MULTIPLE STORIESInteractions between wild and domestic animals can play a role in the maintenance of pathogens and thereby compromise the efficiency of disease control strategies [1,2,3]. Contacts may rely on direct (e.g., mating or fighting) and/or indirect transmission routes (e.g., sharing the same contaminated habitat) and can be influenced by human activities such as farming or hunting [4, 5]. Wild and domestic swine are at risk of inter-population transmission because they belong to the same species and share the same community of potential pathogens [4, 5, 7]. In this context, certain farming practices (use of shared pasture areas, reduced surveillance of the herd, etc.) can facilitate interactions and have a strong influence on the transmission and circulation of pathogens. The risk of transmitting pathogens is considered the highest in areas with traditional extensive farming and can determine the dynamics of emerging or reemerging pig diseases [10]

Objectives

Methods

Results

Discussion

Conclusion