PRRS status is determined through the evaluation of PRRSV shedding and PRRSV exposure.
PRRSV shedding is indicated by the presence of the virus in blood or oral fluids, with the potential for transmission and infection of other animals. A herd with positive shedding status is considered to be unstable.
The presence of anti-PRRSV antibodies in the blood indicates recent exposure to PRRSV, although this is not necessarily accompanied by shedding. Notably, it is impossible to distinguish antibodies against wild-type virus from antibodies against a vaccine.
is based on the presence of PRRSV in blood samples or oral fluids
is based on the presence of anti-PRRSV antibodies in blood samples
Classification of herds based on PRRS status helps to identify objectives for controlling and/or eliminating the virus.
For example, if both the breeding herd and the growing pig herd are unstable, and transmission of PRRSV is occurring both among and between sows and growing pigs, the primary objective of the PRRS control programme may be stabilisation of the breeding herd (i.e. prevention of shedding in the breeding herd).
Classification of herds based on PRRSV transmission
|Breeding herd||Growing pig herd||Transmission||Intervention objective|
|Positive, unstable||Positive, unstable||Vertical and horizontal||Stabilise breeding herd|
|Positive, stable||Positive, unstable||Horizontal||Stabilise growing pig herd|
|Positive, stable||Negative||None||Eliminate virus in breeding herd|
Rerence: Angulo JR (2013). Systematic PRRS Problem Solving, a 5-Step Process. Presentation given at BISA Gold 2013, Ames, Iowa, USA. Holck JT and Polson DD (2003). 2003 PRRS Compendium Producer Edition. Chapter 6: The Financial Impact of PRRS Virus. Holtkamp DJ, Polson DD, Torremorell M; and committee members Morrison B, Classen DM, Becton L, Henry S, Rodibaugh MT, Rowland RR, Snelson H, Straw B, Yeske P and Zimmerman J (2011). Terminology for classifying swine herds by porcine reproductive and respiratory syndrome virus status. Journal of Swine Health and Production, 19 (1), pp 44 – 56.