Understanding PRRSV Infection Dynamics in Growing Pigs in Control and Elimination Programs

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 report by Dr. Jose Angulo regarding PRRS infection dynamics in growing pigs.

Key Points

  • Growing pigs play an important role in regional PRRSV spread.
  • There was an association between prevalence of PRRSV infection in growing pig sites and risk of outbreaks in sow farms.
  • Learning about PRRSV infection dynamics in growing pigs and associated risk factors should help manage pig flows to minimize PRRSV incidence and /or risk of dissemination.
Continue reading “Understanding PRRSV Infection Dynamics in Growing Pigs in Control and Elimination Programs”

Assessing internal personnel movements in swine farms to help direct PRRS control and elimination efforts

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 the preliminary results of a study conducted by Dr. Andreia Arruda at Ohio State University.

Key points

  • Newly developed beacon-sensing technology can be used to better understand within-farm people movement; and particularly better quantify potentially “risky” movements in PRRS positive herds during control/ elimination efforts.
  • Preliminary data analysis showed that an increase in commonly referred to “risky” movements (e.g. from loading areas/ nurseries to other parts of the farm) was associated with a decrease in number of pigs weaned per sow; and an increase in pre-weaning mortality.
Continue reading “Assessing internal personnel movements in swine farms to help direct PRRS control and elimination efforts”

Project Invitation: Assessing within-herd PRRS variability and its impact on production parameters

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, Dr. Arruda and her numerous collaborators invite you to participate in a project.

We know that PRRS virus mutates and evolves quickly. We know there can be co-circulation of PRRS variants in a herd, and even within a single animal. We don’t know whether that can impact health and production. We don’t know how that affects the way we are currently sampling and assessing virus similarity within herds over time.

Project main goal:

This project aims to examine within-herd PRRSV variability over time for sow and growing pig sites under different PRRS immunity strategies (vaccinated, negative and positive herds), and investigate the association between within-herd PRRS variability and health and production parameters of interest to swine producers. We partnered up collaborators with a wide range of expertise to use whole genome sequencing (WGS) to provide insights on the likelihood of PRRS outbreaks

Objective 1:

Describe PRRSV quasispecies within farms using a sample of farms of different demographic types and PRRS management strategies over a one-year time span; and investigate whether PRRSV variability has an impact on health and production outcomes.

Objective 2:

Investigate and compare the use of WGS and different ORFs to determine the best predictor to identify and relate viruses within swine herds.

Objective 3:

Correlate PRRSV variants with production and disease metrics being due to “normal” within-herd virus evolution, vs. new PRRS introductions. And we will also look into the effect of PRRSv variants in production

Request:

We are looking to enroll 6 farms for this project, that has a duration of 1 year:

3 breeding herds (farrow-wean):

  • 1 “naïve” herd (no PRRS for at least last 2 years) that just had an outbreak (farm will be enrolled as a new outbreak happens)
  • 1 “vaccinated” herd (a herd that had a PRRS outbreak and has been vaccinated since then at least twice a year with a MLV)
  • 1 “naturally exposed” herd (a herd that had an outbreak in the past year but is no longer exposing or vaccinating animals (herd will be still eligible if gilts are exposed off site and brought in after testing negative)

3 growing pig herds (finisher or wean-finish):

  • 1 “naïve” herd (no PRRS for at least last 2 years) that just had an outbreak (farm will be enrolled as a new outbreak happens)
  • 1 “vaccinated” herd (a herd that vaccinates each batch of animals using a MLV)
  • 1 “positive” herd (a herd that had an outbreak in the past and is regularly exposed to live virus or a herd that is receiving known positive pigs from a positive source.

We would work with your veterinarian and your team to coordinate the submission of ~16 samples total in a monthly basis for 1 year (12 samplings). These samples will include a combination of processing fluids, oral fluids, and tonsil scrapings. All samples will be sent to the University of Minnesota monthly. Diagnostics is paid. Also, sharing production data will be a requirement.

Best of Leman 2018 series #3: J.Angulo – Understanding PRRSV infection dynamics in growing pigs in control and elimination programs

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 third presentation for this year is from Dr. Jose Angulo from Zoetis and Dr. Paul Yeske from Swine Vet Center regarding PRRS infection dynamics in growing pigs.

Click on the image below to see his presentation at the conference:


Science Page: To filter or not to filter, that’s not the question anymore!

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, Drs. Torremorell and Janni explain what is new in the world of air filtration.

Key Points

  • There are multiple components that affect the effectiveness of filtration for a particular farm.
  • Virus concentrations, particle size, and prevalence of particle size impact virus concentration within the barn.
  • Filtration type and functionality over season can also affect virus concentration within the barn.

Long gone are the days when we debated whether it’s beneficial to install air filtration in a farm. If you are in a high dense area and you have new breaks often enough that filtration pays off, then filtrate! Whether it is the removal of virus from the air (which is what filters do), or the enhancement and enforcement of basic biosecurity measures which are part of the “filtration package”, air filtration has been shown to reduce the number of PRRSV (porcine reproductive and respiratory syndrome virus) breaks.

However, filtration has not always met farm owner expectations. Retrospective data analysis from the Morrison Swine Health Monitoring Project suggests that PRRSV incidence hasn’t been reduced as much as we had hoped for, although it’s still better than no filtration.

So, what can be going on?

To help producers and veterinarians to contrast and compare filtration options and to help understand the components that affect filtration, we created a model that estimates the theoretical number of airborne viruses that would enter a barn through either filters or through leakage given certain assumptions.

The model takes into account various inputs considered important to affect filtration and provides a look at the interaction between ventilation rate, building leakage, filter particle removal efficiency and particle size distribution where viruses may attach.

We have learned a few things already.

First, and the obvious one, is that filtering ventilation air does decrease virus concentration inside filtered barns. Second, ambient virus concentrations and their size distributions, which are largely unknown, have a large impact on virus concentration inside the barn. Although we have done some measurements of virus distribution based on particle size, the relative distribution is likely affected by various factors such as environmental conditions, type of virus, source of virus aerosol, etc.

In general we can say that if viruses are found mostly in the smallest particles (<1 microns), MERV 14 filters will do quite poorly since their lowest removal efficiency is for particles less than 1 micron (~ 76% removal efficiency). In contrast, if the largest amount of virus is found in medium and large particles (>1 micron), as our studies suggest, then MERV 14 filters should do quite well and the more viruses there are in the largest particles (>3 microns), the better MERV 14 filters do and in this case performance is similar to MERV 16 filters.

However, since virus particle size distribution is likely to change throughout the day and season, the only way to minimize the impact of virus particle size distribution is by using higher MERV rating filters with removal efficiencies above 95 % if not more. But, the overall importance of filter collection efficiencies is uncertain because the ambient virus concentrations and their size distributions are not really known.

The other point that is important to recognize is that there are higher barn virus concentrations with lower mechanical ventilating rates and higher barn leakage rates. In other words, during low ventilation rates (i.e. winter) the number of virus particles per cubic feet per minute is higher than during high ventilation rates (i.e. summer). However, when we consider total amount of virus particles that may enter the barn per minute, then higher ventilation rates result in higher in-barn virus concentration compared to lower ventilation rates. This observation is important also when considering positive ventilated barns since it is not uncommon that in the winter, they operate at higher flow rates than negative ventilated barns resulting in the potential introduction of more viruses through the filter, even though leakage is nearly eliminated.

Lastly, as it is well known reducing barn static pressure drop by increasing filter area helps reduce leakage and virus concentrations in the barn. So, it is not a question whether air filtration helps, but rather knowing which factors to consider when making the best of air filtration. Our model does not measure risk of PRRSV infection into a farm but it shows a fairly complex, not always obvious, interaction between ventilation rate, building leakage, filter particle removal efficiency and viral particle size distribution that knowing it, may be useful to producers and veterinarians when evaluating air filtration systems for sow farms.

For more information about the model, contact Kevin Janni (kjanni-at-umn.edu) or Montse Torremorell (torr0033-at-umn.edu) at the University of Minnesota.