Effect of mucin 4 allele on susceptibility to experimental infection with enterotoxigenic F4 Escherichia coli in pigs fed experimental diets.

BACKGROUND: This study investigated the validity of the DNA-marker based test to determine susceptibility to ETEC-F4 diarrhoea by comparing the results of two DNA sequencing techniques in weaner pigs following experimental infection with F4 enterotoxigenic Escherichia coli (ETEC-F4). The effects of diet and genetic susceptibility were assessed by measuring the incidence of piglet post-weaning diarrhoea (PWD), faecal E. coli shedding and the diarrhoea index. RESULTS: A DNA marker-based test targeting the mucin 4 gene (MUC4) that encodes F4 fimbria receptor identified pigs as either fully susceptible (SS), partially or mildly susceptible (SR), and resistant (RR) to developing ETEC-F4 diarrhoea. To further analyse this, DNA sequencing was undertaken, and a significantly higher proportion of C nucleotides was observed for RR and SR at the XbaI cleavage site genotypes when compared to SS. However, no significant difference was found between SR and RR genotypes. Therefore, results obtained from Sanger sequencing retrospectively allocated pigs into a resistant genotype (MUC4-), in the case of a C nucleotide, and a susceptible genotype (MUC4+), in the case of a G nucleotide, at the single nucleotide polymorphism site. A total of 72 weaner pigs (age ~ 21 days), weighing 6.1 ± 1.2 kg (mean ± SEM), were fed 3 different diets: (i) positive control (PC) group supplemented with 3 g/kg zinc oxide (ZnO), (ii) negative control (NC) group (no ZnO or HAMSA), and (iii) a diet containing a 50 g/kg high-amylose maize starch product (HAMSA) esterified with acetate. At days five and six after weaning, all pigs were orally infected with ETEC (serotype O149:F4; toxins LT1, ST1, ST2 and EAST). The percentage of pigs that developed diarrhoea following infection was higher (P = 0.05) in MUC4+ pigs compared to MUC4- pigs (50% vs. 26.8%, respectively). Furthermore, pigs fed ZnO had less ETEC-F4 diarrhoea (P = 0.009) than pigs fed other diets, however faecal shedding of ETEC was similar (P > 0.05) between diets. CONCLUSION: These results confirm that MUC4+ pigs have a higher prevalence of ETEC-F4 diarrhoea following exposure, and that pigs fed ZnO, irrespective of MUC4 status, have reduced ETEC-F4 diarrhoea. Additionally, sequencing or quantifying the single nucleotide polymorphism distribution at the XbaI cleavage site may be more reliable in identifying genotypic susceptibility when compared to traditional methods.

A Comparison of Diets Supplemented with a Feed Additive Containing Organic Acids, Cinnamaldehyde and a Permeabilizing Complex, or Zinc Oxide, on Post-Weaning Diarrhoea, Selected Bacterial Populations, Blood Measures and Performance in Weaned Pigs Experimentally Infected with Enterotoxigenic E. coli.

The effects of feeding a diet supplemented with zinc oxide (ZnO) or a blend of organic acids, cinnamaldehyde and a permeabilizing complex (OACP) on post-weaning diarrhoea (PWD) and performance in pigs infected with enterotoxigenic E. coli (ETEC) were examined. Additionally, changes in selected bacterial populations and blood measures were assessed. A total of 72 pigs weaned at 22 d of age and weighing 7.2 ± 1.02 kg (mean ± SEM) was used. Treatments were: base diet (no antimicrobial compounds); base diet + 3 g ZnO/kg; base diet + 1.5 g OACP/kg. Dietary treatments started on the day of weaning and were fed ad libitum for 3 weeks. All pigs were infected with an F4 ETEC on d 4, 5 and 6 after weaning. The incidence of PWD was lower in pigs fed ZnO ( p = 0.026). Overall, pigs fed ZnO grew faster ( p = 0.013) and ate more ( p = 0.004) than the base diet-fed pigs, with OACP-fed pigs performing the same ( p > 0.05) as both the ZnO- and base diet-fed pigs. Feed conversion ratio was similar for all diets ( p > 0.05). The percentage of E. coli with F4 fimbriae was affected a day by treatment interaction ( p = 0.037), with more E. coli with F4 fimbriae found in pigs fed ZnO on d 11 ( p = 0.011) compared to base diet-fed pigs. Only significant time effects ( p < 0.05) occurred for blood measures. Under the conditions of this study, inclusion of OACP gave statistically similar production responses to pigs fed ZnO, however pigs fed ZnO had less PWD compared to OACP- and the base diet-fed pigs.

Use of tetanus toxoid as a differentiating infected from vaccinated animals (DIVA) strategy for sero-surveillance of avian influenza virus vaccination in poultry.

Strategies for differentiating infected from vaccinated animals (DIVA) require improvement for increased surveillance of avian influenza (AI), where vaccination is employed to control disease. We propose a novel DIVA approach for chickens using tetanus toxoid (TT) as an exogenous marker independent of serotype and relatedness of circulating and vaccine strains. Of 1779 chickens tested from Australia, Hong Kong and China, 100% were seronegative for TT-specific antibodies without vaccination. Tetanus toxoid adjuvanted to mineral oil was immunogenic in chickens. Co-delivery of both TT and inactivated LPAI (H6N2) vaccines in chickens elicited strong TT and influenza-specific antibody responses, which persisted to 53 weeks post-vaccination. Furthermore, immunization with a combined vaccine composed of TT and AI induced high levels of antibodies to both antigens. We conclude that TT is a highly suitable exogenous marker for AI vaccination in chickens allowing simple and effective monitoring of AI vaccination status.