Optimizing an infection model for E. coli diarrhea in newly weaned pigs

Project 21-02 - Dr. Vahab Farzan

The most obvious impacts of enterotoxigenic E. coli post weaning diarrhea (ETEC-PWD) are the economic losses, significant reduction in animal welfare, and indirect increase in use of antimicrobials. A precise infection model is required to evaluate the potential impact of alternative methods such probiotics and vaccines on controlling enterotoxigenic E. coli (ETEC) diarrhea in pigs. One of the issues in the E. coli challenge model is a considerable variation in piglet responses to ETEC which can mainly explained by the fact that the pigs’ response to ETEC infection may be dependent on several factors including pig sources, pig genetics, breed, age, diet, gut microbiome, dose of infection, stomach acidity, and ETEC ability to adhere the intestine epithelial cells.

Objectives:

1. Evaluate the response to enterotoxigenic E. coli (ETEC) F4 among susceptible and resistant pigs (based on MUC4 polymorphism) challenged with different dosages and at different ages.
2. Compare the response to ETEC challenge in susceptible pigs weaned at different ages.
3. Determine the impact of infection dosage on post-weaning diarrhea in susceptible pigs challenged with ETEC.
4. Determine the pig susceptibility to E. coli (ETEC) F4 infection based on CHCF1 polymorphism.

Overall, 57.9% of 601 pigs and 40.3% of 144 pigs tested for inclusion in the trial were susceptible to ETEC-F4 infection based on MUC4 and CHCF1 gene, respectively. The susceptible pigs (based on MUC4) were more likely to have diarrhea than resistant pigs while there was no association between the CHCF1 pig susceptibility and diarrhea. However, both MUC4 and CHCF1 susceptible pigs shed higher levels of ETEC in feces and had more bacterial colonization in their ileum than resistant pigs. Pigs challenged with a higher infectious dosage of ETEC were more likely to demonstrate diarrhea than control pigs. Further, diarrhea was higher among pigs born to primiparous sows compared to those pigs born to multiparous sows.  Weaning age was not associated with diarrhea and bacterial shedding.

The findings indicate that MUC4 gene alone may not be sufficient to identify the susceptible pigs to ETEC, and additional genetic markers such as the polymorphism in the CHCF1 should be considered to examine the pigs for genetic susceptibility to ETEC. The challenge dose used in this study, could increase the rate of diarrhea and bacterial shedding without causing mortality. Altogether, the parameters examined in this study could be implemented to evaluate the efficacy of methods for controlling post-weaning diarrhea in pigs before utilizing on swine farms.