Experimental Evaluation of FaecalEscherichia coliand Hepatitis E Virus as Biological Indicators of Contacts Between Domestic Pigs and Eurasian Wild Boar

Abstract

Domestic pigs and Eurasian wild boar (Sus scrofa) share several important viral and bacterial pathogens. Therefore, direct and indirect contacts between domestic pigs and wild boar present a risk of pathogen spillover and can lead to long-term perpetuation of infection. Biological indicators could be a powerful tool to understand and characterize contacts between wild boar and domestic pigs. Here, faecal Escherichia coli and Hepatitis E virus (HEV) were explored as potential biological indicators under experimental conditions. The data gained in our pilot study suggest that faecal E. coli can be used as biological indicator of contact between wild boar and domestic pig. For HEV, faecal transmission was also confirmed. However, molecular studies on full-genome basis did not reveal markers that would allow tracing of transmission direction. Based on these promising results, future field studies will especially target the practicability of E. coli microbiome molecular typing as surrogate of contacts at the wildlife-livestock interface.

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

“…E. coli were isolated in 87.5% of the wild boar sampled (7/8) in the WB GPS group. With one to six E. coli clones per sample (mean 2.57), this number is slightly lower than in our previous study in captive animals (mean 3.00–3.63 E. coli clones per sample; [Barth et al., ]). From the animals of the WB GPS group, one wild boar excreted three individual E. coli Xba I clones; each of these clones was also found in at least two different domestic pigs of group DP 1 , directly connecting this wild boar with five different samples from DP 1 pigs.…”

“…A laboratory contamination between the samples was excluded as the samples were processed on different days. Similarly, in our previous experimental study, one clone present in the faeces of one donor wild boar was spread to different recipient domestic pigs, whereas other domestic pigs housed together in one pen did not acquire one of the wild boar clones (Barth et al., ). The likelihood of transmission and colonization may be influenced by diverse individual factors related to host behaviour (e.g., individual faecal shedding quantity of E. coli , or snuffling, wallowing and rooting behaviour) and bacterial properties (e.g., the capacity of the respective E. coli strain to survive in the environment [number of bacteria shed and their viability in faeces, environment or stomach during ingestion] or its endowment with genes affecting persistence).…”

“…The quantification and isolation of coliform bacteria from the faeces as well as the storage of single colonies were performed as described previously (Barth et al., ). Briefly, up to ten putative E. coli isolates were isolated from each faecal sample according to the colony morphology on MacConkey, Gassner and sheep blood agar (Sifin Diagnostics GmbH, Berlin, Germany).…”

“…Contour‐clamped homogeneous electric field‐pulsed‐field gel electrophoresis (CHEF PFGE) and cluster analysis were performed as previously described (Barth et al., ; Geue et al., ). In addition to restriction with Xba I, selected agarose plugs were digested with 15 U Ava II or 15 U Spe I (New England Biolabs GmbH, Frankfurt/Main, Germany) at 37°C ( Spe I 18 hr, Ava II 5 hr).…”

“…Therefore, genetic similarities in the gut microbiome between different populations can be used to infer direct or indirect interactions that could facilitate exchange of microorganisms, including pathogen spread. In the case of pig species, this method was recently assessed experimentally and it was demonstrated that at least in captivity, indirect contact between wild boar and domestic pigs is traceable by faecal E. coli isolates (Barth et al., ). However, application of this method in the field has never been tested.…”