Outbreaks of post-weaning diarrhea caused by ETEC F4 are strongly associated with CHCF1 genotype in Danish pigs

Enterotoxigenic Escherichia coli (ETEC) of fimbriae types F4 and F18 causes post-weaning diarrhea (PWD) in pigs and susceptibility relates to host genotype. We examined if CHCF1/FUT1 genotypes were associated with ETEC-mediated PWD in seven Danish herds. Diarrhea was assessed in 1,919 pigs by evaluating perianal fecal staining in the first week after weaning. From each herd, twelve diarrheic and twelve non-diarrheic pigs were selected for genotyping, fecal dry matter (FDM) and microbiological testing. ETEC F4 diarrhea occurred only in CHCF1 heterozygous (RS) pigs. Furthermore, CHCF1 RS pigs had higher odds of diarrhea (Odds ratio (OR) 2.09; p = 0.026) and lower mean FDM (13.9%) than homozygous resistant (RR) pigs (18.6%; p = 0.0052). ETEC F4 was more frequently isolated from CHCF1 RS pigs compared to RR pigs (OR 8.88, p = 0.00005). Additionally, hemolytic E. coli shedding was higher in CHCF1 RS pigs (mean 47.4% vs. 24.1%; p = 0.00001). Too few FUT1 RR pigs were found for analyzing association between FUT1 genotypes and ETEC F18-mediated diarrhea. In conclusion, CHCF1 genotype was strongly associated with ETEC F4-mediated PWD under production settings. ETEC F4 resistance in pigs could help to reduce PWD occurrence and antibiotic use.