Subclinical colitis associated with moderately hemolytic Brachyspira strains

Our latest addition to the swine group at the University of Minnesota College of Veterinary Medicine is Dr. Matheus Costa whose research interests are in pathogen virulence mechanisms and more specifically swine dysentery and streptococcal meningitis.

In this latest publication in the Journal of Swine Health and Production, Dr. Costa and his former collaborators from the University of Saskatchewan introduced less-known Brachyspira strains and what their consequences are on the clinical level for the pig.

Summary

Objective: Microbiological and virulence characterization of 2 moderately hemolytic Brachyspira strains.

Materials and methods: Clinical isolates were obtained from diarrheic (3603-F2) and healthy (G79) pigs. Phenotypic characterization included assessment of hemolytic activity on blood agar and biochemical profiling. Genotyping was performed by sequencing the nicotinamide adenine dinucleotide oxidase (nox) gene, whole genome sequencing, and comparison to relevant Brachyspira. Pig inoculation included 4 treatment groups in 2 challenge experiments: negative control (sterile broth media; n = 12), positive control (Brachyspira hampsonii genomovar 2 strain 30446; n = 18), and 3603-F2 (n = 12) or G79 (n = 12). Fecal scoring and rectal swabbing for culture were performed daily. Animals were euthanized following onset of mucohemorrhagic diarrhea or between 21 and 28 days post inoculation (dpi). Gross and microscopic pathology were assessed. Terminal colon samples were used to characterize post-infection mucosal ion secretion.

 Hematoxylin and eosin (HE; bar = 200 µm) and Warthin-Faulkner (WF; bar = 20 µm) stained porcine colon from the challenge experiments. A) Negative control pig with normal colon, HE stain. B) Negative control pig with no spirochetes, WF stain. C) Positive control (30446) pig with moderate to severe muconecrotic colitis, HE stain. D) Positive control (30446) pig with many spirochetes in glands (arrows), WF stain. E) Strain 3046-F2 inoculated pig with moderately increased mucus, minimal necrosis and mild colitis, HE stain. F) Strain 3046-F2 inoculated pig with small numbers of spirochetes in glands (arrows), WF stain. G) Strain G79 inoculated pig with a mild mucus increase and minimal colitis, HE stain. H) Strain G79 inoculated pig with occasional glands containing many spirochetes (arrows), WF stain.

Results: Both strains were moderately hemolytic. Whole genome and nox sequencing identified 3603-F2 as Brachyspira murdochii and G79 as a novel strain. Both challenge trials revealed intestinal colonization, but no mucohemorrhagic diarrhea. Sporadic watery diarrhea was induced by 3603-F2 associated with a pattern of microscopic lesions similar to pigs with swine dysentery (positive controls). No diarrhea was observed in G79 inoculated pigs, but microscopic lesions were more severe than in controls. Both strains induced greater colonic anion secretory potential than negative controls 21 dpi.

Implications: Allegedly avirulent Brachyspira species most closely related to B murdochii can be associated with subclinical colitis and may be a concern for grow-finish pigs.

Effect of litter aggregation and pooling on detection of PRRS virus in piglet processing fluids

The MSHMP team, led by Dr. Carles Vilalta published a new article in the Journal of Veterinary Diagnostic Investigation regarding the effect of pooling on the detection of PRRS in processing fluids.

The MSHMP team has been one of the first to publish data on the detection of PRRS in processing fluids. You may find all of our previous articles on processing fluids here.

Objectives of the study

  • Identify the limit of PRRS virus detection in pooled processing fluids
  • Evaluate the effect of pooling on the initial Ct value
Continue reading “Effect of litter aggregation and pooling on detection of PRRS virus in piglet processing fluids”

Mycoplasma hyopneumoniae variability highlights the need for new terminology

In this latest article published in Transboundary and Emerging Diseases, Dr. Alyssa Betlach, phD candidate in Dr. Maria Pieters lab, reviews the observed variability in Mycoplasma hyopneumoniae, the effect it can have in swine farms and how a better terminology is possible to improve scientific communication.

Continue reading “Mycoplasma hyopneumoniae variability highlights the need for new terminology”

Comparison of individual, group and environmental sampling strategies to conduct influenza surveillance in pigs

In this new scientific publication from Dr. Jorge Garrido, PhD candidate from the Torremorell lab, numerous sampling strategies to monitor influenza were compared. the following individual, litter, and environmental samples were included in the study:

  • Nasal swabs
  • Nasal wipes
  • Oropharyngeal swabs
  • Oral fluids
  • Surface wipes
  • Udder wipes
  • Airborne particle deposition
  • Air
Continue reading “Comparison of individual, group and environmental sampling strategies to conduct influenza surveillance in pigs”

Effect of strain-specific maternally-derived antibodies on influenza A virus infection dynamics in nursery pigs

A new scientific article from the Torremorell lab, about the influence of maternal antibodies on influenza dynamics was published in PLoS ONE.

The study followed 10 cohorts of nursery piglets form a single influenza-positive sow farm and compared influenza dynamics based on the vaccination status of the dam.

Continue reading “Effect of strain-specific maternally-derived antibodies on influenza A virus infection dynamics in nursery pigs”