Rodrigo C. Paiva and Marcelo N. Almeida, Iowa State University; and Lucina Galina Pantoja, PIC
Escherichia coli (E. coli) is a gram-negative bacterium that can cause various diseases in pigs, including neonatal diarrhoea, septicaemia and mastitis. In recent years, the Veterinary Diagnostic Laboratory at Iowa State University has reported an increase in post-weaning diarrhoea cases caused by E. coli, particularly since 2019.
Increase in cases and changes in pathogenicity
Between 2010 and 2018, the F18 and K88 fimbria types were balanced among E. coli isolates. However, during the rise in post-weaning colibacillosis diagnoses, the F18 type became predominant, accounting for 77.9% of cases. Several factors may underline this phenomenon, such as changes in antimicrobial practices, increased antibiotic resistance and the ineffectiveness of immunological interventions.
One of the most compelling hypotheses is the genetic susceptibility of certain pig breeds to E. coli F18. The expression of specific receptors in the enterocytes, which allow adhesion of this bacterium, is regulated by the FUT1 gene. Mutations in this gene affect susceptibility, with pigs carrying the FUT1AA genotype being resistant, while those with FUT1GA or FUT1GG genotypes are susceptible.
Study objective
This study aimed to evaluate the effect of a contemporary, highly virulent E. coli F18 isolate in pigs with different FUT1 genotypes.
Methodology
Twenty 21-day-old pigs (10 susceptible and 10 resistant) were selected and housed under controlled conditions at Iowa State University. After an acclimation period, all pigs were inoculated with an E. coli F18 isolate and monitored daily for diarrhoea severity and bacterial shedding via faecal samples.
Results
The results showed that although there were no significant differences in E. coli shedding between the two groups, the susceptible group had higher faecal scores, indicating more severe diarrhoea. Additionally, the susceptible group showed a notably higher mortality rate, whereas the resistant pigs had no mortality at all.
Histological analysis revealed that none of the resistant pigs showed colonisation by E. coli in the small intestine, in contrast to 90% of the susceptible pigs.
Conclusions
This study confirms that genetic resistance to E. coli F18 is effective against contemporary high-virulence isolates. Pigs with the resistant genotype showed no signs of disease, while susceptible pigs presented severe clinical symptoms, including mortality and histological lesions.
The research suggests that despite ongoing environmental exposure to E. coli, genetic resistance mechanisms offer a promising avenue for improving pig health and managing associated diseases. Understanding these genetic factors is crucial for developing effective strategies in the swine industry.
Commentary by Pablo Magallón Verde, Technical Services Director, PIC Southern Europe
The article’s conclusions highlight the growing importance of genetic resistance in the fight against pig diseases, particularly in a context where the use of additives such as zinc oxide and antibiotics is being reduced. In particular, colibacillary diarrhoea in the post-weaning phase poses a challenge for the swine industry, and genetic selection for resistant lines is already a fundamental tool to improve animal health, industry sustainability and farm productivity.
At PIC, we continue working on various lines of research and development enabled by genetics to enhance animal robustness and welfare.
