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PRRS 5-Step Process

PRRS 5-Step Process for Pigs

This process has been established to ensure the appropriate placement of Ingelvac® PRRS vaccines in pig herds.

Step 1: Identify Desired Goals

As with any initiative, it is important to clearly identify the desired goals upfront in order to clarify and manage expectations. With the goals identified, a specific protocol can be designed to help achieve the desired outcomes. While individual goals may vary among veterinarians and producers, the control of PRRS in growing pigs is the common goal.

Step 2: Determine Current Status

Knowing when PRRS field virus exposure occurs is necessary to ensure appropriate timing of vaccination in pigs. The use of PRRS ELISA serology tests and PCR assays will provide the necessary understanding of PRRS virus exposure dynamics for a specific flow.

 

The following items should be determined prior to establishing a vaccination protocol:

A) Determine if grow-finish PRRS virus exposure exists

Performance data or mortality rates may be the first sign of a PRRS challenge, or historical diagnostic results may have already alerted you to PRRS virus in your grow-finish herd.

If you are unsure if PRRS virus is present in the grow-finish population, a cross-sectional serology profile with the PRRS ELISA and/or PCR test will answer this important question.

If PRRS exposure does not occur in your herd from weaning to market, PRRS vaccine may not be needed.

If PRRS exposure is demonstrated, proceed to step B.

B) Determine piglet PRRS infection status at weaning

The next step to determining if a group of pigs is a candidate for vaccination is to understand the PRRS status at weaning.If the current status is unknown, a typical diagnostic protocol may be as follows:

Sample 30 head of weaned pigs from each of 2 weaning groups which are between 1 and 4 weeks apart. Samples are then tested by PRRS PCR in pools of 5 samples per pool.

If the current status is unknown, a typical diagnostic protocol may be as follows:

Sample 30 head of weaned pigs from each of 2 weaning groups which are between 1 and 4 weeks apart. Samples are then tested by PRRS PCR in pools of 5 samples per pool.

~ If pools are PCR negative at weaning proceed to step C.

~ If pools are PCR positive at weaning proceed to step D.

C) Piglets are negative at weaning

Determine if there is enough time prior to PRRS virus exposure for vaccination to be maximally effective:

Vaccination should occur at least 4 weeks prior to the onset of PRRS virus exposure as measured by the PRRS PCR, to maximize the impact of vaccine. Negative PCR, or ≤ 20% PCR positive pool test results on serum pools from piglets 4 weeks following the desired time to vaccinate (typically at weaning), assures appropriate timing of vaccination.

D) Piglets are positive at weaning

Determine if there is a likelihood of economic benefit to piglet vaccination even if a portion of the pigs may be infected at the time of vaccination.

If results from the example diagnostic protocol in step B indicate that consecutive cases contain ≤ 20% PRRS PCR positive pools (i.e.,2 weaning groups, 1-4 weeks apart have ≤ 1 positive pool each), consider beginning weaning-age pig vaccination. Although a small proportion of pigs are PRRS positive at the time of vaccination, vaccination still has the potential to generate an economic benefit by protecting the majority of the population not yet infected. If results indicate that there is a higher rate of positive PCR pools at weaning, working toward sow farm stabilization for PRRS prior to implementing piglet vaccination should be the first step to improving your downstream pig performance.

Step 3: Understand Current Constraints

Since each herd or location is unique, it is important to understand the specific constraints or risks for PRRS infection in each situation. The use of BreedingHerd and Growing Pig PRRS Risk Assessments through the American Association of Swine Veterinarians are recommended.

The following questions are examples that may be considered to ensure understanding of the PRRS situation in your system and the proper use of PRRS vaccines.

  • What are the sources of PRRS virus infection in this flow of pigs?
  • Are offspring from multiple sow sources commingled to create this pig flow? If so, do the sow sources have the same or different PRRS statuses?

Step 4: Develop Solution Options

It is important to work with your herd veterinarian to assess your current PRRS situation and together, ensure you develop a solution option that is best for your operation.

The common benefit of using vaccines is to improve herd health, which in turn improves economic return.

The following is recommended to maximize the benefits of PRRS vaccination in pigs.

  • Vaccinate pigs at least 4 weeks prior to the onset of PRRS virus exposure as measured by the PRRS PCR test, or at least 6 weeks prior to seroconversion as measured by the PRRS ELISA test.
  • Vaccinate entire populations to generate the most consistent and uniform immune response.

Step 5: Implement and Monitor the Preferred Solution

Once the vaccination program has been implemented it is recommended that biologic and economic benefits be measured to confirm the value of vaccination for PRRS control in pigs.

 

*PRRS PCR assessment of pigs at weaning. **Studies demonstrate the benefit of vaccinating growing pigs when PRRSV prevalence is low(<20% positive PCR pools). This decision should be made under the direct consultation of a veterinarian.1,2

REFERENCES

  1. J. Waddell, et.al. Modified live PRRS virus vaccination of nursery pigs as an essential component of a comprehensive PRRS control program. IPVS, 2008.
  2. Boehringer Ingelheim Vetmedica Inc., Internal data. Unpublished at this time.

©2017 Boehringer Ingelheim Vetmedica, Inc.

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