Control of PRRS in breeding stock

Vaccination and/or partial or total depopulation strategies, test and removal procedures or acclimatisation of incoming pigs has proven efficient in the eradication of PRRS in breeding herds.

Vaccination

Central to the control of PRRS is prevention of the spread of PRRSV within the pig herd. The herd should be stable with a uniform level of immunity throughout the herd, with no PRRSV-negative pigs.

In breeding herds the modified live vaccines have been used as an aid to creating this uniform immunity.Clinical symptoms are reduced and the infection of piglets prior to weaniing is prevented (Lopez, 2004; Beilage 2003). Vaccines have also been used with success within stock replacement policies, to induce immunity prior to introduction of the new stock ( Dee, 1997).

Depopulation

In Denmark eradication of PRRSV at farm level using partial or total depopulation. In a study by Andreasen eradication was successful in 15 of 20 pig herds in which partial depopulation was applied and in all of the four herds employing total depopulation.

Depopulation is expensive. It is only effective if strict biosecurity is applied and if all the pig farms in the affected region are following the same strategy. On the other hand, a combination of depopulation and vaccination is an interesting alternative option for control.

Test and removal

Dee (2000) and Torremorell (2000) have shown that it is possible to eradicate PRRSV from breeding herds using a test and removal protocol respective an intensive elimination protocol including partly depopulation. Both strategies were applied on stable herds.

It has also been experienced that herds become PRRSV negative over time following strict biosecurity and management principles (Geiger 2002).