fbpx
Sign up now!
Don't show this again
Download the report!Continue to Site >
or wait 7 secs

Thank you for confirming your subscription!

(And remember, if ever you want to change your email preferences or unsubscribe, just click on the links at the bottom of any email.)

We’re glad you’re enjoying Pig Health Today.
Access is free but you’ll need to register to view more content.
Already registered? Sign In
Tap to download the app
X
Share
X

REPORTS

Collect articles and features into your own report to read later, print or share with others

Create a New Report

Favorites

Read Later

Create a new report

Report title (required) Brief description (optional)
CREATE
X
NEXT
PORK POULTRY
follow us


You must be logged in to edit your profile.

Favorites Read Later My Reports PHT Special Reports
Pig Health Today is equipped with some amazing (and free) tools for organizing and sharing content, as well as creating your own magazines and special reports. To access them, please register today.
Sponsored by Zoetis

Pig Health Today | Sponsored by Zoetis

.
Featured Video Play Icon

Linhares: Digging deeper into PRRS outbreak management

Porcine reproductive and respiratory syndrome (PRRS) has challenged producers and swine veterinarians for decades. During that time, outbreak management and strategies have evolved along with the virus.

“If you ask 20 different people how they are managing PRRS outbreaks, you may get 20 different answers,” Daniel Linhares, DVM, associate professor at Iowa State University (ISU), told Pig Health Today. “People are still trying different things to succeed in their management program.”

To learn more, Linhares is collaborating with Giovani Trevisan, DVM, ISU research assistant professor, in a program called the PRRS outbreak management program (POMP). The effort involves a study similar to one Linhares conducted 10 years ago that looked at how approximately 60 herds managed PRRS breaks between 2009 and 2012. The ISU researchers are now following a similar-sized group of herds that broke with PRRS between 2020 and today.

Three components

 Linhares outlined three different components involved in the POMP study. These include:

  1. Benchmarking how sow farms are managing PRRS outbreaks. “Are they closing the herd? Are they exposing sows or gilts to PRRS virus (PPRSV)? If so, how they’re doing that — with vaccine, live-virus inoculation (LVI) or different approaches,” he noted.
  2. Comparing how long it takes farms to reach a low-PRRS prevalence or start producing negative pigs again, as well as the productivity impact of an outbreak.
  3. Whole-genome sequencing to try to determine how many PRRSV strains were present on farms. Also, whether there were recombinants with the wild-type virus or vaccine. “We looked at diversity — how many unique strains and how does that correlate back to clinical measures, time to stability and time to live production,” Linhares said.

Extended time to stability

The most basic finding was that there remains a wide range of PRRS outbreak-management strategies and outcomes. “We saw a lot of variation between herds that close, don’t close, use the LVI with the wild-type virus or vaccine or a combination of those,” he noted.

A significant finding was that the median time to consistently produce PRRS-negative piglets at weaning takes about 10 weeks longer than previously observed. “The median time to negative is now about 36 weeks,” Linhares said. “If you look at the whole distribution, we had farms that more than a year after the break they were still producing positive piglets.”

An influencing factor was whether the management scheme included herd closure, which is defined as stopping gilt introduction until the infection pressure is low and transmission has ended. “Farms that do herd closure achieved stability much quicker,” Linhares pointed out.

Farms that had some prior immunity through mass exposure via vaccination or LVI also tended to achieve stability much sooner. Batch farrowing, at either 2-week or 4-week intervals to create an all-in/all-out flow, reduced the time to achieve negative piglets as well.

One caveat to the longer time to stability may relate to more sensitive monitoring options today. Linhares noted that 10 years ago, PRRS monitoring involved collecting 30 serum samples once a month. “Today with processing fluids, familial fluids, people are monitoring hundreds of piglets on a weekly or biweekly basis,” he added. “You now have much more sensitive methods to detect at lower prevalence.”

Productivity metrics

Another important metric in determining PRRS-outbreak severity was pre-weaning mortality. “In general, the worst impact in terms of piglets not weaned after a break was almost twice as much as what we observed 10 years ago,” Linhares said.

Back then, the median number of piglets lost was about 2,500 per 1,000 sows. “Today we’re observing 4,700 as a median number of piglets not weaned. So, a much more severe type of break,” he added, citing PRRSV 1-4-4 L1C variant and PRRSV 1-7-4 as influencing factors today.

Different variants

For the third component of the POMP study, Linhares and Trevisan asked the farms’ veterinarians to submit virus samples at the beginning of a PRRSV outbreak, 10 weeks later and just before pigs turned negative. The point was to do whole-genome sequencing of the virus and evaluate genetic properties of the virus associated with clinical expression following the outbreak.

The researchers wanted to know, “was there something in the virus that would help explain that time to stability or time to baseline productivity,” Linhares said. They observed that it was the norm, not the exception, for farms to be infected with more than one PRRSV strain. Upon closer review, it was common to find recombinants between some viruses that are part vaccine virus, part wild-type virus or two different wild-type viruses.

Linhares relayed a very preliminary finding in the dataset of this ongoing study was that when a farm had less virus diversity, it progressed toward PRRS-negative status and recovered baseline productivity more quickly. When multiple strains surface or recombination occurs, it resulted in mortality waves, abortions and other PRRSV-associated clinical signs.

His take-home message is to characterize the PRRSV strain early in the outbreak and check again in 2 to 3 months to verify if it’s the same strain. If there’s evidence of other variants within the herd, “consider additional immunization and closing the grip on internal biosecurity, biomanagement and biocontainment measures to prevent virus spread from litter to litter, pen to pen, room to room,” Linhares said. “You want to make it hard for the virus to transmit and gain ground.”

Share It
Porcine reproductive and respiratory syndrome (PRRS) has challenged producers and swine veterinarians for decades. During that time, outbreak management and strategies have evolved along with the virus.

Click an icon to share this information with your industry contacts.



Posted on February 2, 2022

tags:
RELATED NEWS



You must be logged in to edit your profile.

Share It
Effective PCV2 control relies on vaccination of healthy pigs before they become infected. But what do you do in unstable herds whose sows give birth to viremic pigs?

Click an icon to share this information with your industry contacts.
Google Translate is provided on this website as a reference tool. However, Poultry Health Today and its sponsor and affiliates do not guarantee in any way the accuracy of the translated content and are not responsible for any event resulting from the use of the translation provided by Google. By choosing a language other than English from the Google Translate menu, the user agrees to withhold all liability and/or damage that may occur to the user by depending on or using the translation by Google.