Science Page: Why PRRS elimination doesn’t work in some herds

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.

This week, we are sharing an article by Dr. Amber Stricker from Suidae Health and Production, published in PigHealthToday.com

“Over the years, there’s been considerable progress in the development of strategies aimed at eliminating porcine respiratory and reproductive syndrome virus (PRRSV). I define successful PRRSV elimination as the absence of clinical disease in the breeding herd and, more importantly, the absence of the vertical transmission of virus to weaned pigs. Unfortunately, successful PRRS elimination isn’t always achieved in some herds, and I have several experiences that may help answer why.”
Dr. Stricker then compiles six reasons that, in her experience, led to a failure in PRRS elimination:
  • No break in disease cycle or insufficient herd closure
  • Incomplete exposure
  • Compliance problems
  • Holding back pigs
  • New virus introduction
  • Insufficient diagnostics

Take a look at the full article to read more about each of those facors.

Science Page: Natural and experimentally-induced Senecavirus A infections in boars

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.

This week, we are sharing a study from Dr. Matt Sturos from the University of Minnesota, Veterinary Diagnostic Laboratory regarding Senecavirus A in boars.

Key points

  • Naturally-infected boars have been documented to shed Senecavirus A (SVA) RNA in semen for up to three months after exhibiting vesicular disease.
  • Experimentally-infected boars shed SVA RNA in semen for up to three weeks post-inoculation.
  • The majority of experimentally-infected boars did not exhibit clinical signs or develop apparent lesions.
Senecavirus A in boars
Testis of boar naturally-infected with Senecavirus A. Bright red areas indicate positive signal for SVA by in-situ hybridization.

“This update shows that SVA RNA is shed in semen from both naturally-infected and experimentally-inoculated boars. The prolonged shedding of viral RNA in semen and the presence of SVA RNA in the testes and tonsils of the naturally-infected boars for up to three months are concerning findings and raises the possibility of persistent infection in boars. While the duration of shedding in semen for the experimentally-infected boars was considerably shorter than for the naturally-infected boars, the fact that all contemporary-strain boars had PCR-positive semen on at least one collection indicate that shedding in semen is a repeatable phenomenon and shedding occurred in some boars which did not exhibit clinical signs or develop vesicular lesions. It is currently unknown whether semen from infected boars can serve as a source of infection if used to inseminate susceptible females.”

 

Science Page: Multiple influenza viruses circulate in growing pigs during epidemic events

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.

This week, we are sharing a study from Dr. Andres Diaz and the Torremorell lab.

Key points

  • The diversity of influenza A viruses in growing pigs is dynamic
  • Influenza A viruses can replicate as a swarm of viruses that are identical, closely related to each other (>99%), or clearly distinct (H1 vs. H3 subtypes)
  • Influenza A viruses of the same genotype can re-infect pigs within a short period of time.
132 3-week old piglets selected at weaning and placed in a wean-to-finish farm were sampled weekly for 15 weeks (n=2080 samples). Samples were tested by RT-PCR and the complete genome of influenza was obtained from 93 samples using next generation sequencing.
Two epidemic waves of IAV infection were detected with 3 distinct viral groups (VG swarms) found (VG1, VG2 and VG3). An H1 gamma (VG1) dominated the first outbreak, an H3 (VG3) dominated the second outbreak and an H1 beta (VG2) was only recovered when none of the two other viruses dominated.
The complete version of this study can be found online in open-access.

Science Page: Uterine prolapses trend in production sow herds

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.

This week, we are sharing a study from Dr. Carmen Alonso and collaborators at Elanco.

Objectives of the study:

The objectives of the study, were: 1) to analyze the trends in prolapses of sows from 2012 to 2016, and 2) to evaluate the role of management practices, production parameters, and PRRS and PED disease status as covariates in the trend analysis of uterine sow prolapses.

Key points:

  • Uterine prolapse primarily affects sows around parturition and is still defined by an uncertain list of verified etiologies.
  • Since early 2013, swine companies have been experiencing an increase in the incidence of uterine prolapses in their herds.
  • Understanding the trends and potential risk factors would be crucial to improve the economics and welfare of the affected sow farms.

Uterine prolapses significant variables Alonso Results from this study indicate that the percentage of prolapsed sows has consistently increased every year (significant from 2014-2016) as a percentage of total deaths with the incidence being higher during the winter months and the lowest during the summer months. Total born, the use of toxin binder, assistance during farrowing, and PED health status had an association to sow deaths with prolapse per sows farrowed.

Click here to read the entire report on Uterine prolapses trends.

Science Page: Describing the cull sow and cull hog market networks in the US: A pilot project

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.

This week, we are sharing a project from Dr. Jim Lowe at the University of Illinois.

Project rationale

“What is the range of locations of sows that enter a slaughter plant?, How many stops along the way do they make? and How long do they remain the slaughter channel?” These are the questions this project is planning to answer.

Key Points:

  • Little is known about the cull market, how culls are transported, and how they play a role in disease spread.
  • While most sows travel directly to slaughter, an important percentage most likely move through multiple collection points.
  • Cull sow movement are important for understanding disease transport related epidemiology.

Premise ID tags were collected during an entire week at a cull harvest plant. Animals originated from 297 unique source farms, located in 21 US states and Canada.

distance from farm to marketResults are shown in the histogram on the left.

The majority of culls (86%) originate less than 240km from the final collection point. This interaction is deemed to be a primary interaction, meaning that it is very likely the culls moved direct from the farm of origin to the final collection point. 14% of the culls travel a distance greater than 240km to the terminal collection point. Of these 14%, 17.7% or 2.5% of all culls, traveled 5 times as far to the last point of collection from the farm than they did from collection point to plant.

Click here to see the entire report on the cull sows and cull hogs market.