Wild Boars as Reservoir of Highly Virulent Clone of Hybrid Shiga Toxigenic and Enterotoxigenic Escherichia coli Responsible for Edema Disease, France.

Alexandre Perrat,Marie-Hélène Bayon-Auboyer,Geoffrey Petit,Frédéric Auvray,Silvia Turci,Vladimir Grosbois,Eric Oswald,Hubert Brugère,Anouk Decors,Priscilla Branchu

doi:10.3201/eid2802.211491

Abstract

Edema disease is an often fatal enterotoxemia caused by specific strains of Shiga toxin–producing Escherichia coli (STEC) that affect primarily healthy, rapidly growing nursery pigs. Recently, outbreaks of edema disease have also emerged in France in wild boars. Analysis of STEC strains isolated from wild boars during 2013–2019 showed that they belonged to the serotype O139:H1 and were positive for both Stx2e and F18 fimbriae. However, in contrast to classical STEC O139:H1 strains circulating in pigs, they also possessed enterotoxin genes sta1 and stb, typical of enterotoxigenic E. coli. In addition, the strains contained a unique accessory genome composition and did not harbor antimicrobial-resistance genes, in contrast to domestic pig isolates. These data thus reveal that the emergence of edema disease in wild boars was caused by atypical hybrid of STEC and enterotoxigenic E. coli O139:H1, which so far has been restricted to the wildlife environment.

Highlights

Edema disease is an often fatal enterotoxemia caused by specific strains of Shiga toxin–producing Escherichia coli (STEC) that affect primarily healthy, rapidly growing nursery pigs
Most postweaning diarrhea (PWD) F4-positive enterotoxigenic E. coli (ETEC) are of the serogroup O149, whereas F18-positive ETEC belong to many serogroups, including O138, O139, O141, O147, and O157, because the F4 or F18 fimbriae gene cluster and enterotoxin genes are encoded on conjugative plasmids that result in their spread [1]
Core Genome–Based Phylogenetic Analysis We performed short-read whole-genome sequence analysis of 28 STEC O139:H1 strains isolated from wild boars that had clinical signs and lesions consistent with edema disease (ED) during multiple outbreaks that occurred in the southeast of France: in the Ardèche Department in 2013 (n = 5), 2014 (n = 6), 2015 (n = 8), and 2016 (n = 2) and in the Drôme Department in 2019 (n = 7) (Appendix 1 Table 1)

Summary

Introduction

Edema disease is an often fatal enterotoxemia caused by specific strains of Shiga toxin–producing Escherichia coli (STEC) that affect primarily healthy, rapidly growing nursery pigs. The strains contained a unique accessory genome composition and did not harbor antimicrobial-resistance genes, in contrast to domestic pig isolates These data reveal that the emergence of edema disease in wild boars was caused by atypical hybrid of STEC and enterotoxigenic E. coli O139:H1, which so far has been restricted to the wildlife environment. Neonatal enteric colibacillosis and postweaning diarrhea (PWD) are other crucial factors contributing to death in nursery pigs in global swine production These diseases are caused by enterotoxigenic E. coli (ETEC), which produce heat-stable toxins (STa, STb), heat-labile toxins (LT), or both. Given the increase of the wild boar population in Europe in the last decades [16], which can lead to more frequent contact with domestic pigs and increasing risk for disease transmission [17], we characterized the strains responsible for the emergence of ED in wild boars. We sequenced the whole genome of 28 wild boar STEC O139:H1 isolates from the different ED outbreaks and performed a genetic and genomic comparison with STEC O139:H1 and non-O139:H1 strains isolated from domestic pigs and other sources worldwide

Methods

Results

Conclusion