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New perspectives to the enterotoxigenic E. coli F4 infection model in weanling piglets in relation to the susceptibility genotypes and bacterial shedding
Post-weaning diarrhea caused by enterotoxigenic E. coli (ETEC) is a major problem in weaner piglets. Responses of individual animals to ETEC infection are very different and show high varieties in animal experiments with ETEC infection. The aim of this study was to optimize the ETEC F4ac infection model in piglets by combining the genotype susceptibility with performance and bacterial shedding.
Prior to weaning 120 male piglets (individual housed) were tested for susceptibility or resistance towards ETEC O149:F4ac by a DNA marker based test. After weaning (27 ± 2-d-of-age) the piglets were orally infected with 5 ml of an inoculum suspension (containing 1.5*108 CFU/ml ETEC F4ac in a 2.5% sucrose solution) at day 7, 8 and 9 after weaning. Fecal bacterial shedding was determined at day 7 (before challenge), 10 and 13 by spreading on CBA plates. Hemolytic colonies were confirmed by an agglutination test with an ETEC F4ac specific antiserum.
In the first week after challenge all (n = 4) homozygote sensitive (SS) animals died. During the same period, feed efficiency (FE) was significant lower (P<0.001) in heterozygote sensitive (RS)-animals (FE = 0.67; n = 61) compared with the homozygote resistant (RR) animals (FE= 0.8; n = 55). After this week the animals started to recover and the feed efficiency differences became less. Diarrhea incidence was significantly different (P<0.001) between genotypes SS (91%) compared to RS (67%) and RR animals (47%) in the first week after challenge. Furthermore while ETEC was hardly detected in the fecal material of the RR animals, they were found in most of the RS animals and in all SS animals (see table).
Table Detection of ETEC in fecal material at day 10 and 13 as grouped by genotype.
Genotype |
Positive both days |
Negative |
Positive at day 10 |
Positive at day 13 |
ND |
Total |
RR |
0 |
51 |
2 |
2 |
0 |
55 |
RS |
35 |
10 |
9 |
6 |
1 |
61 |
SS |
4 |
0 |
0 |
0 |
0 |
4 |
|
120 |
ND= not determined
In conclusion, susceptible animals (RS and SS) compared to resistant animals (RR) animals showed poorer feed efficiency, higher diarrheal incidence and higher numbers of ETEC fecal shedding in the first week after challenge. The DNA marker based test can be used to select animals that are susceptible for ETEC for inclusion in the ETEC infection model.
Keywords:
ETEC F4, infection model, genotype