Experimental model of enterotoxigenic Escherichia coli infection in pigs: potential for an early recognition of colibacillosis by monitoring of behavior.

The hypothesis that altered behavior is a sign for an early recognition of disease was tested. The experiment was conducted to evaluate the behavioral patterns of pigs in a model of postweaning colibacillosis. Twenty-five weaned pigs (from a herd that was previously found to be highly susceptible to F4+ Escherichia coli strains) were randomly assigned into 5 groups, kept in isolated pens under the controlled ambiental conditions. One day after weaning, the pigs from three groups were intragastrically inoculated (via orogastric tube) with either F4ac+ (1466 or 2407) or F4- (1467) nonenterotoxigenic E. coli (non-ETEC) strains, respectively. The pigs from the fourth group were inoculated with F4ac+ ETEC strain M1823 and the remaining 5 pigs that received broth containing 1.2% sodium bicarbonate were kept as noninoculated controls. The pigs were examined daily and the frequency and duration of their behavioral patterns, such as eating, drinking, lying, standing, urinating, defecating, rooting and playing were monitored for 300 h during a period of 10 days. In this model, three conditions were also observed in F4-susceptible pigs: (1) acute fatal diarrheal disease; (2) moderate diarrhea and weight loss and (3) no diarrhea and weight loss. The incidence (both frequency and duration) of defecating was significantly higher (P < 0.05) in pigs inoculated with F4ac+ ETEC strain M1823 as compared to that of noninoculated (control) pigs. Pigs inoculated with F4ac+ non-ETEC strain 1466 had a significantly lower frequency of eating (P < 0.05) and frequency/duration of drinking (P < 0.05) than did the controls. The 1466-inoculated pigs, had an increased diarrhea score, but frequency/duration of defecating was not significantly different. Pigs inoculated with F4ac+ non-ETEC strain 2407 spent more time in lying (P < 0.05) than did noninoculated pigs. Conversely, the pigs that received F4- non-ETEC strain 1467 laid shorter (P < 0.05) and ate/drank less frequently (P < 0.05) than the controls. It was concluded that the changed occurrence of defecating and eating in pigs that were inoculated with either F4ac+ ETEC (M1823) or non-ETEC (1466) strain. respectively, was consistent with the pending clinical disease, i.e. postweaning colibacillosis.

Distribution of immune cells expressing CD3a, CD21 and S-100 protein markers in the porcine gut-associated lymphoid tissues.

The distribution of immune cells within the gut-associated lymphoid tissues (GALT) of swine is highly organized. The appearance of such cells could not be separated from the effects of age, weaning and exposure to environment. Here, we have examined the distribution patterns of a subset of CD3a+ T and CD21+ B cells as well as S-100 protein+ cells and secretory (s) IgA+ cells within GALT compartments (such as jejunal lamina propria = JLP, ileal Peyerís patches = IPP, and mesenteric lymph node = MLN) of juvenile 8-week-old conventionally reared pigs using either two monoclonal antibodies (mAbs) or polyclonal antibodies (pAbs) in the immunohistochemical staining techniques with avidin-biotin complex (ABC) or peroxidase-antiperoxidase complex (PAP), respectively. The most potent porcine T-cell marker--CD3 surface antigen--is expressed as CD3a epitope on ileal intraepithelial lymphocytes, and numerous lymphocytes in the extrafollicular areas of MLN and dome region of IPP. Conversely, the cells expressing CD21 surface molecules were only demonstrable in the interfollicular areas of MLN and in the germinal centers of IPP. A strong reaction to sIgA was displayed by the plasma cells in the lumen of crypts and those residing the lamina propria of jejunum and ileum. The S-100 protein+ cells were numerous in JLP around the crypts and in IPP of weaned pigs. Both applied mAbs proved to be useful reagents for phenotypic and functional analyses of porcine lymphoid cell subsets by the ABC technique. However, further investigation of the S-100 protein marker is needed to determine which (if any) subset of porcine CD3+ CD4- CD8+ T cells could be designated as orthologue of human CD8+ CD11b+ suppressor T cells.