An observational field study of porcine post-weaning diarrhea: clinical and microbiological findings, and fecal pH-measurements as a potential diagnostic tool

Metallo-Glycodendrimeric Materials against Enterotoxigenic Escherichia coli

Conjugation of carbohydrates to nanomaterials has been extensively studied and recognized as an alternative in the biomedical field. Dendrimers synthesized with mannose at the end group and with entrapped zero-valent copper/silver could be a potential candidate against bacterial proliferation. This study is aimed at investigating the bactericidal activity of metal-glycodendrimers. The Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction was used to synthesize a new mannosylated dendrimer containing 12 mannopyranoside residues in the periphery. The enterotoxigenic Escherichia coli fimbriae 4 (ETEC:F4) viability, measured at 600 nm, showed the half-inhibitory concentration (IC50) of metal-free glycodendrimers (D), copper-loaded glycodendrimers (D:Cu) and silver-loaded glycodendrimers (D:Ag) closed to 4.5 × 101, 3.5 × 101 and to 1.0 × 10-2 µg/mL, respectively, and minimum inhibitory concentration (MIC) of D, D:Cu and D:Ag of 2.0, 1.5 and 1.0 × 10-4 µg/mL, respectively. The release of bacteria contents onto broth and the inhibition of ETEC:F4 biofilm formation increased with the number of metallo-glycodendrimer materials, with a special interest in silver-containing nanomaterial, which had the highest activity, suggesting that glycodendrimer-based materials interfered with bacteria-bacteria or bacteria-polystyrene interactions, with bacteria metabolism and can disrupt bacteria cell walls. Our findings identify metal-mannose-dendrimers as potent bactericidal agents and emphasize the effect of entrapped zero-valent metal against ETEC:F4.

The cotton swab method: an accurate and less invasive way to assess fecal consistency in weaned pigs

BACKGROUND

Researchers and pig veterinarians are interested in assessing pigs' fecal consistency. This study developed a standardized protocol and scale for the cotton swab method, which is a way of assessing the fecal consistency in pigs. The accuracy of the cotton swab method was evaluated in weaned pigs using fecal dry-matter analysis as a golden standard. The study also proposed fecal dry-matter percentage thresholds for the categorization of fecal consistency on a four-point scale.

RESULTS

The thresholds of 10.3%, 16.6%, and 21.9% fecal dry-matter were suggested for categorization of the consistency of fecal samples on a four-point scale. The accuracy of the cotton swab method was high. The agreement to the four-point fecal consistency score derived from the fecal dry-matter percentage was almost perfect (weighted Gwet's agreement coefficient = 0.87 [95% confidence interval: 0.84; 0.91]). The cotton swab method had a sensitivity of 85.0% (95% confidence interval: 76.5; 91.4) and a specificity of 95.2% (95% confidence interval: 92.0; 97.3) when used to diagnose whether pigs had diarrhea or not. For non-diarrheic pigs, the method almost always (n = 287/289) required less handling than the collection of a fecal sample by digital rectal manipulation.

CONCLUSION

The cotton swab method is an accurate way to assess fecal consistency in pigs, both on a four-point scale and as a dichotomous diarrhea score. The method is quick to perform and less invasive than methods relying on the collection of fecal samples. New fecal dry-matter thresholds between feces of different consistencies were proposed.

A Virus-like Particle-Based F4 Enterotoxigenic Escherichia coli Vaccine Is Inhibited by Maternally Derived Antibodies in Piglets but Generates Robust Responses in Sows

F4-positive enterotoxigenic Escherichia coli is associated with diarrhea and poor growth outcomes in neonatal and newly weaned piglets and is thus a major economic and welfare burden in the swine industry. Vaccination of sows with F4 fimbriae protects against the neonatal disease via passive transfer of maternal immunity. However, this strategy does not protect against infection post-weaning. Consequently, prevention and treatment methods in weaner pigs heavily rely on the use of antimicrobials. Therefore, in order to reduce antimicrobial consumption, more effective prophylactic alternatives are needed. In this study, we describe the development of a capsid virus-like particle (cVLP)-based vaccine targeting the major F4 fimbriae subunit and adhesion molecule, FaeG, and evaluate its immunogenicity in mice, piglets, and sows. cVLP-display significantly increased systemic and mucosal antibody responses towards the recombinant FaeG antigen in mice models. However, in piglets, the presence of anti-F4 maternally derived antibodies severely inhibited the induction of active humoral responses towards the FaeG antigen. This inhibition could not be overcome, even with the enhanced immunogenicity achieved via cVLP display. However, in sows, intramuscular vaccination with the FaeG.cVLP vaccine was able to generate robust IgG and IgA responses that were comparable with a commercial fimbriae-based vaccine, and which were effectively transferred to piglets via colostrum intake. These results demonstrate that cVLP display has the potential to improve the systemic humoral responses elicited against low-immunogenic antigens in pigs; however, this effect is dependent on the use of antigens, which are not the targets of pre-existing maternal immunity.

Easy and reliable assessment of the prevalence of porcine post-weaning diarrhoea

Post-weaning diarrhoea is a condition of increasing importance due to recent restrictions and bans on the preventive use of antimicrobials and medicinal zinc oxide. For various purposes, it is valuable to monitor the occurrence of post-weaning diarrhoea. The aim of this paper was to propose a protocol for easy and reliable assessment of the prevalence of post-weaning diarrhoea within a section of pigs as an alternative to clinical examination of a random sample of pigs. Two datasets were collected in two different observational field investigations, including more than 4000 individual clinical examinations of newly weaned pigs. First we identified a clinical marker for post-weaning diarrhoea. Second, we drew samples by simulation from our two dataset using different simplified sampling strategies and compared these to conventional random sampling strategies. The prediction error for estimates of the diarrhoea prevalence within a section was compared for the different sampling strategies. The study showed that pigs with diarrhoea had an increased risk of displaying diarrheic soiling of the hind part as well as dull, long, and bristly hair coat, and possibly also hollow flanks and a suboptimal body condition score. Diarrheic soiling of the hind part was the best clinical predictor of diarrhoea; our best estimate of the diagnostic sensitivity was 76.1% (95% credible interval: 72.0, 79.8), and the specificity was 97.1% (95% credible interval: 96.5 0.97.7). Diarrheic soiling of the hind is only a valid clinical predictor of diarrhoea for the first 14 days after insertion into the nursery unit. The precision and accuracy of prevalence estimates were similar for haphazard sampling compared to random sampling of the pigs. Likewise, sampling from a restricted number of pens produced prediction errors similar to sampling across all pens. Yet, the study had limitations regarding sample sizes, and furthermore it is difficult to provide certainty for absence of effects. We recommend sampling pigs haphazardly within at least three randomly selected pens for post-weaning diarrhoea prevalence surveys in order to easily obtain a reliable prevalence estimate. Based on our findings, we conclude the paper by proposing a simple four-step protocol for surveys of the within-section prevalence of post-weaning diarrhoea.