Highly virulent Escherichia coli causes oedema disease in wild boars

A study led by scientists from INRAE, ENVT and the Université de Toulouse, identified a bacterium potentially lethal for pigs in wild boars in France. The findings, published in Emerging Infectious Diseases, show that the emergence of oedema disease in wild boars was caused by a new hybrid strain of Escherichia coli, which so far has been restricted to the wildlife environment.

Outbreaks of oedema disease were observed in wild boars in the southeast of France during 2013-2019. Shiga toxin-producing E. coli (STEC) strains isolated from the boars were shown to belong 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.

The researchers say this is the first time that a hyper-virulent strain of E. coli of this kind has appeared in wildlife. At the moment, the strain is only circulating in wild animals and does not display any antibiotic resistance genes – a common feature of bacteria from livestock farms. They recommend surveillance of this highly pathogenic clade in the wild boar population to study its spread in the wildlife reservoir and potential transmission to domestic pigs.

Article: Perrat, A., Branchu, P., Decors, A., Turci, S., Bayon-Auboyer, M. H., Petit, G., Grosbois, V., Brugère, H., Auvray, F., Oswald, E. (2022). Wild boars as reservoir of highly virulent clone of hybrid Shiga toxigenic and enterotoxigenic Escherichia coli responsible for edema disease, France. Emerging Infectious Diseases, 28(2), 382-393, doi: 10.3201/eid2802.211491