Lawsonia intracellularis infected enterocytes lack sucrase-isomaltase which contributes to reduced pig digestive capacity.

Lawsonia intracellularis is endemic to swine herds worldwide, however much is still unknown regarding its impact on intestinal function. Thus, this study aimed to characterize the impact of L. intracellularis on digestive function, and how vaccination mitigates these impacts. Thirty-six L. intracellularis negative barrows were assigned to treatment groups (n = 12/trt): (1) nonvaccinated, L. intracellularis negative (NC); (2) nonvaccinated, L intracellularis challenged (PC); and (3) L. intracellularis challenged, vaccinated (Enterisol® Ileitis, Boehringer Ingelheim) 7 weeks pre-challenge (VAC). On days post-inoculation (dpi) 0 PC and VAC pigs were inoculated with L. intracellularis. From dpi 19-21 fecal samples were collected for apparent total tract digestibility (ATTD) and at dpi 21, pigs were euthanized for sample collection. Post-inoculation, ADG was reduced in PC pigs compared with NC (41%, P < 0.001) and VAC (25%, P < 0.001) pigs. Ileal gross lesion severity was greater in PC pigs compared with NC (P = 0.003) and VAC (P = 0.018) pigs. Dry matter, organic matter, nitrogen, and energy ATTD were reduced in PC pigs compared with NC pigs (P ≤ 0.001 for all). RNAscope in situ hybridization revealed abolition of sucrase-isomaltase transcript in the ileum of PC pigs compared with NC and VAC pigs (P < 0.01). Conversely, abundance of stem cell signaling markers Wnt3, Hes1, and p27Kip1 were increased in PC pigs compared with NC pigs (P ≤ 0.085). Taken together, these data demonstrate that reduced digestibility during L. intracellularis challenge is partially driven by abolition of digestive machinery in lesioned tissue. Further, vaccination mitigated several of these effects, likely from lower bacterial burden and reduced disease severity.

Effect of Tetracycline Dose and Treatment Mode on Selection of Resistant Coliform Bacteria in Nursery Pigs.

This study describes the results of a randomized clinical trial investigating the effect of oxytetracycline treatment dose and mode of administration on the selection of antibiotic-resistant coliform bacteria in fecal samples from nursery pigs. Nursery pigs (pigs of 4 to 7 weeks of age) in five pig herds were treated with oxytetracycline for Lawsonia intracellularis-induced diarrhea. Each group was randomly allocated to one of five treatment groups: oral flock treatment with a (i) high (20 mg/kg of body weight), (ii) medium (10 mg/kg), or (iii) low (5 mg/kg) dose, (iv) oral pen-wise (small-group) treatment (10 mg/kg), and (v) individual intramuscular injection treatment (10 mg/kg). All groups were treated once a day for 5 days. In all groups, treatment caused a rise in the numbers and proportions of tetracycline-resistant coliform bacteria right after treatment, followed by a significant drop by the time that the pigs left the nursery unit. The counts and proportions of tetracycline-resistant coliforms did not vary significantly between treatment groups, except immediately after treatment, when the highest treatment dose resulted in the highest number of resistant coliforms. A control group treated with tiamulin did not show significant changes in the numbers or proportions of tetracycline-resistant coliforms. Selection for tetracycline-resistant coliforms was significantly correlated to selection for ampicillin- and sulfonamide-resistant strains but not to selection for cefotaxime-resistant strains. In conclusion, the difference in the dose of oxytetracycline and the way in which the drug was applied did not cause significantly different levels of selection of tetracycline-resistant coliform bacteria under the conditions tested.IMPORTANCE Antimicrobial resistance is a global threat to human health. Treatment of livestock with antimicrobials has a direct impact on this problem, and there is a need to improve the ways that we use antimicrobials in livestock production. We hypothesized that antibiotic resistance development following treatment of diarrhea in nursery pigs could be reduced either by lowering the dose of oxytetracycline or by replacing the commonly used practice of flock treatment with individual or small-group treatments, since this would reduce the number of pigs treated. However, the study showed no significant difference between treatment groups with respect to the number or proportion of tetracycline-resistant coliforms selected. The most important conclusion is that under practical field conditions, there will be no added value, in terms of lowering resistance development, by exchanging flock treatment for individual or small-group treatment of nursery pigs. The reason for the lack of an effect of single-animal treatment is probably that such animals share the environment with treated animals and take up resistant bacteria from the environment.

Association between average daily gain, faecal dry matter content and concentration of Lawsonia intracellularis in faeces.

BACKGROUND: The objective of this study was to investigate the association between average daily gain and the number of Lawsonia intracellularis bacteria in faeces of growing pigs with different levels of diarrhoea. METHODS: A longitudinal field study (n = 150 pigs) was performed in a Danish herd from day 29 to 47 post weaning. Every third day all pigs were weighed, subjected to a clinical examination and faecal samples were obtained. Faecal samples were subjected to dry matter determination and absolute quantification by PCR for L. intracellularis and porcine circovirus type 2 (PCV2). Association between average daily gain, faecal dry matter content, numbers of L. intracellularis bacteria and PCV2 genome copies in faeces was investigated in a multilevel mixed-effects linear model. RESULTS: Increasing numbers of L. intracellularis log10 bacteria/g faeces were significantly associated with decreasing average daily gain (P < 0.001). The association was decreasing with increasing faecal dry matter content (P < 0.01). The number of PCV2 log10 copies/g faeces was not significantly associated with average daily gain of the pigs (P > 0.5). CONCLUSION: The results suggest a potential application of a PCR quantifying L. intracellularis in growing pigs. Faecal dry matter content must be taken into consideration in interpretation of such test results.

Distribution and chemical coding of intramural neurons in the porcine ileum during proliferative enteropathy.

Enteric neurons are highly adaptive in their response to various pathological processes including inflammation, so the aim of this study was to describe the chemical coding of neurons in the ileal intramural ganglia in porcine proliferative enteropathy (PPE). Accordingly, juvenile Large White Polish pigs with clinically diagnosed Lawsonia intracellularis infection (PPE; n=3) and a group of uninfected controls (C; n=3) were studied. Ileal tissue from each animal was processed for dual-labelling immunofluorescence using antiserum specific for protein gene product 9.5 (PGP 9.5) in combination with antiserum to one of: vasoactive intestinal polypeptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), somatostatin (SOM), neuropeptide Y (NPY) or galanin (GAL). In infected pigs, enteric neurons were found in ganglia located within three intramural plexuses: inner submucosal (ISP), outer submucosal (OSP) and myenteric (MP). Immunofluorescence labelling revealed increases in the number of neurons containing GAL, SOM, VIP and CGRP in pigs with PPE. Neuropeptides may therefore have an important role in the function of porcine enteric local nerve circuits under pathological conditions, when the nervous system is stressed, challenged or afflicted by disease such as PPE. However, further studies are required to determine the exact physiological relevance of the observed adaptive changes.

Lawsonia intracellularis proliferative enteropathy in a foal.

A weanling foal was diagnosed with proliferative enteropathy caused by Lawsonia intracellularis based on history, clinical findings of depression, anorexia, weight loss, colic, diarrhea, and ventral edema, and a combination of serology and fecal PCR. An epidemiological investigation on the premises revealed that many of the other foals and adult horses were seropositive for L. intracellularis, despite being clinically normal, and identified a dog as a potential carrier and source of infection for the foal. The foal was successfully treated with a combination of azithromycin and rifampin.