1. Whole herd-depopulation/repopulation
2. Test and removal
3. Herd closure and rollover
4. Production of negative pigs from positive sows

Advantages and disadvantages of each method are as follows:

1. Whole herd depopulation repopulation

Advantages:

• High degree of efficacy
• Solves multiple disease problems at the same time
• Results in genetic improvement
• Vast experience of veterinary industry

Disadvantages:

• Costly
• Requires multiple sites for off-site breeding of new clean stock and finishing out of diseased pigs
• Re-infection can occur during repopulation process

2. Test and Removal

Advantages:

• High degree of efficacy
• Low risk, due to speed of the testing process

Disadvantages:

• Testing cost can be high if ELISA and PCR are used to test sera
• Requires removal of exposed breeding animals
• Feasible only in herds with low (<10%) seroprevalence in breeding herd

3. Herd closure and rollover

Advantages:

• Initial efficacy appears promising
• Does not require excessive testing or removal of breeding animals

Disadvantages:

• Requires off site breeding facilities
• Requires a long time to complete
• Relies on consistent natural exposure of all replacement gilts and a lack of PRRSV transmission in the breeding herd over time.
• Questionable if this can be accomplished in all cases.

4. Production of negative pigs from positive sows

Advantages:

• Preserves genetics
• Can improve overall health status of offspring through the use of medication or specific vaccinations
• Improvements in health and performance of offspring can be significant

Disadvantages:

• Transmission of PRRSV from dam to offspring can result in production of infected batches of weaners

Source: University of Minnesota Swine Extension - May 2006