Best of Leman 2018 series #9: K. VanderWaal – Can we predict PRRS and PED outbreaks?

We launched a new series on the blog last year. Once a month, we are sharing with you a presentation given at the Allen D. Leman swine conference, on topics that the swine group found interesting, innovative or that lead to great discussions.

We can find all of the presentations selected from last year’s conference on the blog here.

Our ninth presentation is from Dr. Kim VanderWaal, our colleague at the University of Minnesota, who gives us a glimpse into a future when producers might be able to know when their farms are at risk of disease outbreaks.

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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.


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.

PRRS incidence rate by status at break

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

Key points

  • Current PRRS Chart 3 incidence risk by status does not take into account the time at risk farms contribute to each status.
  • Incidence rate takes into account the time a farm is at risk of disease.
  • Chart 3 will be replaced by a incidence rate chart that reflects more accurately the PRRS outbreak rate by status.
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A podcast on sow mortality: what is new?

Podcasts are a perfect way to get caught up with new swine information! We are presenting you the latest episode from “At The Meeting… Honoring Dr. Bob Morrison” in collaboration with SwineCast.

In this episode of At the Meeting honoring Dr. Bob Morrison, the group discusses sow mortality.

Dr. John Deen from the University of Minnesota shares his expertise with podcasts hosts Dr. Montse Torremorell, Dr. Gordon Spronk and Dr. Tom Wetzell.

Sow mortality continues to be an issue in swine production over North America. It used to be an issue 20 years ago but has made a come back at the forefront of producers’ mind.

Listen to the podcast (17 minutes)

For those of you who would like to read some more about Dr. Jason Ross’s project, his slides from the 2018 Allen D. Leman swine conference can be found online.

Happy 4th of July for our readers in the United States!

What is the impact of zinc in late-gestation diets?

Image by Tim McReynolds from Pixabay

Our colleagues in the College of Food, Agricultural and Natural resource Sciences (CFANS) have shared one of their latest projects with the National Hog Farmer readers. They found that adding higher amounts of zinc in the late-gestation diet of sows in both a research and commercial herd increased the survival of smaller piglets until they are weaned.

Continue reading “What is the impact of zinc in late-gestation diets?”