The 5 step process to PRRS control

01-05-2015


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1- IDENTIFY DESIRED GOALS

 
The first step is often the most overlooked. Simply stated, where do you want your herd to be in the PRRS story? Ask yourself: What is my goal? There are three common goals: 
1) Control the effects of the disease and improve health/performance;
2) eliminate the virus; or
3) prevent the virus from introduction/reintroduction once achieving PRRS-negative status.
 
WHAT IS YOUR GOAL?
 
Control
 
PRRS has been confirmed in the herd, and preventing new virus introductions is unlikely. Farm management is committed to moving toward stability by managing risk factors (internal and external) to minimize transmission and maximize immunity.
Most producers will work toward PRRS control (with the goal of weaning PRRS-negative pigs), simply because the likelihood of re-exposure to the PRRS virus is high. These farms tend to be in more pig-dense areas with higher PRRS exposure risk.
 
Eliminate
 
Farms seeking to eliminate PRRS from their operation have successfully stopped resident PRRS virus circulation within the herd, are consistently weaning PRRS virus–negative piglets and have a low risk of new PRRS virus introduction from outside.
These farms tend to be more isolated, in less pig-dense areas or areas with lower PRRS exposure.
 
Prevent
 
These herds have eliminated all internal risks (resident virus circulation) and minimized external (virus exposure from outside the farm) risks, have tested negative for wild-type virus, and have a completely naïve breeding herd.
The current focus is on preventing introduction of the virus through biosecurity. 
 

2- DETERMINE CURRENT PRRS STATUS


Whatever your stated goals, it’s important to understand where PRRS has or has not been present in your herd. The testing of blood, oral fluids and the environment may be essential in obtaining your current status.
 
KNOW THE SYMPTOMS
 
Recognizing clinical signs of PRRS is important to spotting the disease early. Work with your herd veterinarian to further diagnose if any of these symptoms are present:
 
Breeding-Herd Symptoms
 
·       Late-term abortions
·       Premature farrowing
·       Delivery of stillborn, weak/listless/non-viable or mummified piglets
·       Anorexia and fever
·       Sow mortality
 
Growing-Pig Symptoms
·       Fever, depression, reduced appetite
·       Discharge from eyes and nose
·       Respiratory symptoms; specifically, labored abdominal breathing often referred to as “thumping”
·       Uneven growth, gaunt appearance
·       Increased culls and mortality post-weaning
 
TESTING
 
Which Test Is Right for You?
 
PRRS infection is widespread in U.S. herds, so care must be taken to both confirm an active infection and to rule out other infectious diseases. Any tentative clinical diagnosis should be confirmed by detection of the PRRS virus. The most common diagnostic tests used for confirming PRRS include:
·       Polymerase chain reaction (PCR) – Detects presence of virus
·       ELISA – Detects presence of antibody following infection
·       Gene sequencing – Differentiates PRRS virus strains
 
The primary sample types that can be collected and used for diagnostic testing include:
·       Blood/Serum
·       Oral fluids
·       Tissues (lung, tonsil and/or lymph node)
·       Environmental samples
 
Sample Diagnostic Testing for Replacement Gilts:
 
 

ENTRY INTO GILT POOL EXITING GILT POOL/PRIOR TO BREEDING-HERD ENTRY
Blood/Serum – PCR and ELISA Blood/Serum – PCR and ELISA
Oral – PCR Oral – PCR
 
 
Sample Diagnostic Testing for Sows:
 
ROUTING MONITORING/TESTING DUE-TO-WEAN PIGLETS
Blood/Serum – PCR
 
Testing Growing Pigs for PRRS
 
8–10 WEEKS OF AGE (15–20 PIGS) 12–14 WEEKS OF AGE (15–20 PIGS) 18–20 WEEKS OF AGE (15–20 PIGS)
Blood/Serum – PCR and ELISA Blood/Serum – PCR and ELISA Blood/Serum – PCR and ELISA
Oral – PCR Oral – PCR Oral – PCR

 
Tissue samples can be used to further confirm disease. Always work with your veterinarian when developing a diagnostic testing program and collecting samples.
 
TIPS FOR BEST SAMPLE COLLECTION
Detection of PRRS virus is best performed in affected pigs during the early stages of PRRS infection:
·       Weak-born, lethargic newborn/neonatal pigs
·       Weak, off-feed and feverish post-weaned pigs
·       Sows/Gilts exhibiting clinical signs, recently aborted, feverish and/or off-feed
 
Good choices for diagnostic samples and tissues for virus detection methods include:
·       Blood/Serum
·       Oral fluids
·       Lung, lymph node, tonsil and/or spleen tissues
 
Other tips:
·       Collect samples and immediately refrigerate/place on ice.
·       Both fresh and formalin-fixed tissue samples, if possible.
·       Send samples overnight to a laboratory using an insulated box with ice packs.
·       Completely fill out laboratory submission form.
 

3- UNDERSTAND CURRENT CONSTRAINTS

It is important to understand all the risks you and your operation face against porcine reproductive and respiratory syndrome (PRRS). Today’s pig industry is highly mobile. Pigs are moved from farm to farm, barn to barn, and even across state lines. The better you understand the risks, the better you can take steps to reduce or eliminate them.
 
 
INTERNAL RISKS
Understand internal risks in order to minimize transmission and maximize immunity to reduce chronic resident virus circulation within the farm.
 
 
EXTERNAL RISKS
Understand external risks to minimize transmission and maximize immunity to reduce non-resident virus introduction/re-introduction from outside the farm.
 
RESTATE YOUR GOALS
 
Control
PRRS has been confirmed in the herd, and preventing new virus introductions is unlikely. Farm management is committed to moving toward stability by managing risk factors (internal and external) to minimize transmission and maximize immunity. Most producers will work toward PRRS control (with the goal of weaning PRRS-negative pigs), simply because the likelihood of re-exposure to the PRRS virus is high. These farms tend to be in more pig-dense areas with higher PRRS exposure risk.
 
Eliminate
Farms seeking to eliminate PRRS from their operation have successfully stopped resident PRRS virus circulation within the herd, are consistently weaning PRRS virus-negative piglets, and have a low risk of new PRRS virus introduction from outside. These farms tend to be more isolated, in less pig-dense areas or areas with lower PRRS exposure.
 
Prevent
These herds have eliminated all internal risks (virus circulation within the farm) and minimized external risks (virus exposure from outside the farm), have tested negative for wild-type virus, and have a completely naïve breeding herd. The current focus is on preventing introduction of the virus through biosecurity. 

4- DEVELOP SOLUTION OPTIONS


 The goals of an effective porcine reproductive and respiratory syndrome (PRRS) control strategy should be to:
·       prevent new PRRS virus introduction
·       reduce virus spread
·       minimize severity and economic impact
 
PRRS control is much more than just vaccination alone. It requires a systematic approach to PRRS management to achieve long-term success. 
 
PREVENT INFECTION – Eliminate introduction of new PRRS virus by establishing the strongest possible biosecurity and pig flow management.
 
MAXIMIZE IMMUNITY – Establish and maintain uniform immunity in the whole herd.
 
MINIMIZE TRANSMISSION/EXPOSURE – Reduce circulation of resident virus using a PRRS control program tailored to the needs of each farm, which includes biosecurity, pig flow management and immunity management.
 
BREEDING HERD CONTROL
 
To control PRRS in the breeding herd, a possible solution would be:


·       Load-Close-Expose protocol
1.     Load the farm with replacement gilts — enough inventory to maintain closure
2.     Close the farm for as long as possible, preferably 200+ days
3.     Expose the breeding herd via mass vaccination in order to generate uniform immunity throughout the breeding-herd population
4.     Reopen the herd only to gilts that have been vaccinated prior to introduction to the breeding herd, with the goal to be immune and non-infectious (via diagnostics – ELISA-positive and PCR–negative) at entry to breeding herd when reopened
5.     Perform quarterly mass vaccination of sow herd to maintain stability
6.     Monitor your PRRS status through diagnostics in order to confirm stability

 
Studies show benefits of using vaccination to achieve PRRS stability in a load-close-expose protocol
 
Work closely with your herd veterinarian to diagnose PRRS and determine the right course of action for your operation.
 
 
ELIMINATE
 
Once you have controlled the spread of wild-type PRRS virus, there are several possible options for eliminating the virus form your herd.
 
·       Option A – Conduct a “Depop/Repop”
1.     Remove entire pig population from the site
2.     Clean/disinfect/dry (Decontaminate environment.)
3.     Repopulate with naïve/PRRS-negative animals
4.     Monitor your PRRS status through diagnostics in order to maintain/confirm PRRS-negative status
 
·       Option B – Load-Close-Expose
1.     Load the farm with replacement gilts — enough inventory to maintain closure
2.     Close the farm for as long as possible, preferably 200+ days
3.     Expose the breeding herd via mass vaccination in order to generate uniform immunity throughout the breeding-herd population
4.     Reopen the herd only to gilts that have been vaccinated prior to introduction to the breeding herd, with the goal to be immune and non-infectious (via diagnostics — ELISA-positive and PCR-negative) at entry to breeding herd when reopened
5.     Perform quarterly mass vaccination of sow herd to maintain stability
6.     Monitor your PRRS status through diagnostics in order to confirm stability
 
·       Option C – Herd closure alone
1.     Close the farm for as long as it takes to generate uniform population immunity and non-infectious status (as measured by diagnostics); length of closure is variable due to many factors (e.g., farm size, virus strain)
2.     This protocol depends on using wild-type virus circulation/infection to build natural immunity – there is no vaccine used and there can be no new entries to the farm
3.     Wild-type virus will die out and be cleared from the population
4.     Move positive animals out and negative animals in
 
Note: Herd closure alone (Option C) typically takes longer to build uniform immunity than through a load-close-expose approach (Option B).
 
 
PREVENT
 
Once you have eliminated the PRRS virus from your operation, take steps to prevent virus introduction/re-introduction.
 
1.     Completely eliminate PRRS virus via depop/repop, load-close-expose or herd closure – the herd must be naïve/PRRS-negative
2.     Ongoing repopulation with naïve/PRRS-negative animals only
3.     Monitor your PRRS status through diagnostics in order to confirm PRRS-negative status
 
Work closely with your herd veterinarian to diagnose PRRS, and determine the right course of action for your operation.
 
GROWING PIGS

 
CONTROL
 
In situations where there is circulating PRRS virus or risk of virus exposure is high in growing pigs, the most common goal is to control the PRRS virus. Best approaches include:
1.     Conduct partial depopulation, removing positive animals
2.     Improve health and performance of pigs
3.     Use vaccination to maximize immunity
a.     For optimum protection, pigs should be vaccinated at least three to four weeks prior to PRRS virus exposure. In most cases, vaccine can be used at or around weaning to provide protection against infection all the way to market. Work with your veterinarian to understand and determine optimum vaccination timing.
4.     Implement a biosecurity plan to minimize virus introduction/reintroduction and transmission
5.     Manage your pig flow to reduce interaction with PRRS–positive pigs
a.     It is recommended to use all-in/all-out by barn (or preferably by site)
 
Work closely with your herd veterinarian to diagnose PRRS, and determine the right course of action for your operation.
 
ELIMINATE
 
In rare occasions, growing pig operations can eliminate PRRS exposure. These operations tend to be in low pig-dense areas with a low risk for virus introduction/re-introduction. Potential options to achieve PRRS virus elimination include:
1.     Conduct depop/repop
2.     Implement vaccination protocol with strategic pig flow
a.      Example
                                               i.     Vaccinate twice — 30 days apart — and close farm for at least eight weeks
                                              ii.     Empty PRRS-positive barns and replace with PRRS-negative animals
                                             iii.     Conduct strict biosecurity between PRRS-negative and PRRS-positive barns until entire farm achieves PRRS-negative status
3.     Monitor your PRRS status through diagnostics in order to confirm PRRS–negative status
 
Work closely with your herd veterinarian to diagnose PRRS, and determine the right course of action for your operation.
 
PREVENT
 
There may be operations in low pig-dense areas who have either successfully eliminated the PRRS virus or have never been exposed.  In these cases, it is important to prevent introduction or re-introduction of the virus.
 
1.     Completely eliminate PRRS virus via depop/repop, load-close-expose or herd closure; the herd must be naïve/PRRS-negative
2.     Ongoing repopulation with naïve/PRRS-negative animals only
3.     Monitor your PRRS status through diagnostics in order to confirm PRRS-negative status
 
Work closely with your herd veterinarian to diagnose PRRS, and determine the right course of action for your operation.

5- IMPLEMENT AND MONITOR PREFERRED SOLUTION
Once your solution options are clearly outlined, you can determine which one(s) should be executed to help achieve your goal of controlling, eliminating or preventing porcine reproductive and respiratory syndrome (PRRS) on your farm.
 
Execution Techniques 
You have designed your solutions. Now it’s time to execute! Follow these strategies to best execute your solutions and meet your goal:
 
1.     Obtain team commitment to work toward same solution.
a.     Clearly communicate the plan to all farm personnel.
b.     Emphasize why the plan, and each step in it, is important, and the importance of each team member’s role in achieving success.
c.     Provide any necessary and ongoing training.
2.     Develop metrics to track results. Communicate to the team what should happen and when it should happen. (Example: To monitor breeding-herd stability, your metrics would be negative PCR tests for PRRS in due-to-wean piglets.)
3.     Maintain team focus through consistent communication and collaboration. What’s worked? What hasn’t worked? What adjustments or changes should be made?
4.     Review the plan regularly with herd veterinarian.
 
Monitoring Tactics 
You’ve done all this work, stated your herd goals, and implemented your solutions. Now it’s time to measure your success.
 
 
Control
·       Ensure that you are not bringing negative/non-immune animals into a positive herd. Doing so can result in a chronic infection situation.
·       Ensure that replacement animals are being adequately prepared/acclimated for entry into your herd.  Remember, the goal is to prepare your replacement gilts to be immune and non-infectious for entry into your PRRS-positive and stable breeding herd.
·       Measure the immune response in replacement animals two to three weeks after vaccination, and also monitor the status of gilts just prior to entry into the breeding herd. Again, the goal is to be immune and non-infectious prior to entry into the breeding herd.
·       Routinely measure virus circulation in due-to-wean pigs via PRRS PCR testing , to understand the PRRS status of your breeding herd.
·       Continue monitoring, working with herd veterinarian, and following biosecurity protocols.
 
 
Eliminate
·       Only introduce PRRS-negative animals when the breeding herd is non-infectious (no evidence of resident PRRS virus circulation) and ready for introductions.
·       Do not introduce PRRS-negative animals until you have had at least three negative environmental PCR tests, and at least three consecutive monthly negative animal tests (typically negative due-to-wean piglet PCR tests).
·       Continue monitoring, working with herd veterinarian, and following biosecurity protocols.
 
 
Prevent
·       Always ensure that replacement gilts are truly naïve/negative.
·       Stay focused on biosecurity protocols, and ensure they are being followed.
·       Be keenly aware of PRRS status in your proximity.
·       Maintain diligent/disciplined focus on identifying and managing external biosecurity risks to prevent entry/introduction of PRRS virus.
·       Continue monitoring, working with herd veterinarian, and following biosecurity protocols.
 
Everyone Can Help 
There's no shame in being a PRRS-positive farm. It is critical that every stakeholder in the industry — farmers, veterinarians, feed suppliers, packers, transportation companies, etc. — understand how the virus is transmitted and their responsibilities to minimize its spread.
 
Communication is critical; as a pig producer, you can talk to all outside visitors (gas company, trash hauler, mail delivery, etc.), as well as surrounding farms, to know and understand where PRRS exists and how it spreads. With this knowledge, delivery routes can be modified and allied industry can focus its efforts.
 

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