PRRSV control - example of a successful program

A 450 sows farrow to finish farm, infected with PRRS-1 in January-February 2018.

The vaccination protocol for this farm was as follows:

Herd was loaded with replacement gifts for 20 weeks use, which was the maximum number of animals that could be housed. This was followed by mass vaccination of all sows/gilts, first time in February 2018 and second time 30 days later.

• Introduction of gilts was planned to week 32-2018 and week 52-2018.
• Replacement stock was placed in separated groups at an acclimatization site situated approximately 500 m from the sow herd, 16 weeks prior to these dates and vaccinated with MLV two times spanned by 30 days.
• The gilts were introduced to the sow herd group-wise during the period.

A modified McRebel, with less restrictions according to foster sows, was implemented in the farrowing rooms. The herd had 18.5 live born pigs pr. sow, so there was a need for making foster sows in order not to lose too many piglets. Foster sows were allowed, but only by establishing a unidirectional flow of pigs:

• All sows were placed with 15-16 pigs, which they almost weaned, because the pigs have access to a milk-system.
• Every week, three-four foster sows with the largest newborn pigs were made, by moving these pigs to a sow with seven days older pigs in the next section.
• The 7 days old pigs were moved to a sow section with 14 days old pigs in next section and her pigs were moved to a sow with 21 days old pigs in next section.
• The 21 days old pigs were weaned.
• All foster sows with newborn pigs were made within the first 24 hours after birth of the pigs.
• Not all sows could take care of 15-16 pigs, so there was a need for another foster sow for hungry pigs when they were 7-14 days old (they would make one pr. section).
• These pigs were moved to a foster sow in the same section and her pigs were moved to a sow in a section with older pigs.

All procedures described above regarding cleaning, hygiene and use of tools was implemented in farrowing rooms.

Weaned pigs were vaccinated with half a dosage MLV from May-October (5 months) on the day of weaning.
In the weaner and finisher sections the following procedures were scheduled:

• AI/AO were practiced in all the weaner sections.
• Daily caretaking started with the youngest pigs.
• Clothes were changed between sections, hands were washed/disinfected.
• Aisles were washed with soap/disinfected/dried out between each movement of pigs (from farrowing rooms to weaner sections and from weaner sections to finisher sections).
• Separate set of equipment and tools for each section.
• Change of needles between each pig.

Monitoring showed that non-vaccinated weaned pigs were PCR negative in December 2018, but a few were positive on serology in February 2019. The elimination plan was reassessed and there was a follow-up on the strategy in the farrowing section. The owner did not want to "risk" more losses by not making foster-sows, as the production results in both sow herd and finisher pigs were back to baseline production. Therefore, the strategy was to continue the strict plans in growing animals.

Based on clinical observations the sow herd seemed to be stable and in week 19 2019, sentinels gilts (non-vaccinated and seronegative) was introduced. Blood samples from these animals showed no seroconversion 8 weeks later. From July 2019 until March 2020 the weaners/finishers has tested negative.