Animal Health


Testing swine oral fluids is a convenient and cost-effective method for PRRS monitoring and surveillance in commercial herds

By collecting the oral fluids remaining after a pig chews on a rope hanging within the pen, individual or groups of pigs can be surveyed for exposure to the Porcine Reproductive & Respiratory Syndrome (PRRS) virus.

  • Cost-effective and convenient
  • Less invasive sample collection
  • Optimized for detection of antibodies in less than four hours
  • 98% specificity and sensitivity
  • For disease monitoring and surveillance

Testing oral fluids provides a more comprehensive picture of herd status compared to bleeding a random selection of the herd. It is also a less invasive means of sample collection. In this comparison, results show that the new IDEXX PRRS OF Ab Test is optimized for the detection of antibodies to PRRSV from individual or collected samples of swine oral fluids (Figure 1), in less than four hours.


Figure 1. Comparison of test protocols

 Comparison of test protocols



This assay follows the same protocol as the IDEXX PRRS X3 Ab Test with the following protocol modifications:

  • Sample input is 50 μl/well (diluted 1:2 in sample diluent to a final volume of 100 μl)
  • There is a 2-hour sample incubation step at room temperature.
  • The final substrate color changes from blue to yellow, so final absorbance is read at 450 nm with a reference wavelength (Aref) of 620 nm to 650 nm (A450 - Aref)

An S/P ≥0.4 is considered a positive result.


Field Studies

Sample Set 1
Oral fluids reference standards: These reference standards are composed of a temporal series of pooled oral fluids collected from pens of pigs vaccinated with type 2 modified live vaccine (Ingelvac® PRRS® MLV, Boehringer Ingelheim Vetmedica Inc.) and collected at at 0, 10, 15, 20, 28, 35, 41, 49, 56, 75, and 91 days postvaccination (DPV).

Sample Set 2
Oral fluids from individual boars: Samples of swine oral fluids paired with serum from boars sampled at -7 to 0 days pre-inoculation (confirmed seronegative status) and 21 days post-inoculation (confirmed seropositive status) were tested with the IDEXX PRRS OF Ab Test and compared with results obtained in paired serum using the PRRS X3 Ab Test. The boar population comprised sets of 24 animals vaccinated with modified live vaccine (MLV), 22 animals inoculated with type I PRRSV strain, 24 animals inoculated with type II PRRSV strain , and an additional set of 10 Austrian pigs vaccinated with type I.

Sample Set 3
Oral fluids from a pen prevalence study: Analysis of performance on pen samples according to prevalence of antibody-positive pigs in a pen was based on a study of 500 pigs divided into pens of 25 pigs each.4 Briefly, pigs vaccinated with modified live vaccine 14 days prior to the day of the study (at peak of seroconversion for antibodies) were introduced into pens of pigs seronegative for PRRS antibodies at a different prevalence of antibody-positive pigs (0%, 4%, 12%, 20%, and 36%), with five pens for each of the prevalence values. All pigs were bled for confirmation of serum antibody titers. Oral fluids were collected from each pen by hanging a cotton rope on the pen for 30 minutes. Five successive 30-minute replicate collections were done per pen by hanging a separate new rope for each collection event.

Pen-based oral fluid samples were collected at various levels of prevalence (0%, 4%, 12%, 20%, and 36%) of vaccinated pigs introduced at 14 days post-vaccination into pens of PRRS-negative pigs (Sample set 3). The IDEXX PRRS OF Ab Test detects anti-PRRS antibodies in ≥96% of all collection events in pens of at least 20% prevalence, and ≥85% in pens of 12% prevalence (Figure 2).


Figure 2. Performance Analysis

Sample Set 1

 Performance Analysis

Sigma Aldrich Idexx Laboratories Romerlabs LP ITALIANA Carl Zeiss
 Thermo Scientific  Nunc Finnpipette QSP  Molecular Bio Products
LI-COR Honeywell MPW