IDEXX PRRS OF Ab Test
Test With Confidence™
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 and
respiratory syndrome (PRRS) virus.
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 Oral Fluids Ab Test (PRRS OF) is optimized for the
detection of antibodies to PRRSV from individual or pen samples of swine
oral fluids in less than four hours (Figure 1).
•Cost-effective and convenient
Figure 1. Comparison of Test Protocols
•Optimized for detection of antibodies in less
than four hours
PRRS Oral Fluids
•98% specificity and sensitivity
Swine Oral Fluid
•For disease monitoring and surveillance
Read at
450-650nm
substrate
50µL sample input/well
30 min
30 min
15 min
STOP
HR
HRP
H
HRRPP
P
30 min
HR
HRP
H
HRRPP
P
conjugate
2h
HR
HRP
H
HRRPP
P
•Less invasive sample collection
PRRS
Antigen
Swine Serum
2.5µL sample input/well
PRRS X3
15 min
STOP
Read at
650nm
IDEXX PRRS OF Ab Test
Protocol
Field Studies
This assay follows a similiar protocol to the
IDEXX PRRS X3 Ab Test with the following
key modifications:
Sample Set 1 (Figure 2)
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 0, 10, 15, 20, 28,
35, 41, 49, 56, 75 and 91 days postvaccination (DPV).2
• 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 ) range
between 620 nm and 650 nm (A450 - Aref ).
An S/P ≥ 0.4 is considered a positive result.
Figure 2. Performance Analysis
Sample Set 1
7
New IDEXX PRRS OF Ab Test
6
S/P
5
4
3
2
1
0
0
10
20
30
40
50
60
DPI (Days Postinfection)
70
80
90
Cutoff S/P =0.4
Sample Set 2 (Figure 3-1 through 3-4)
Oral fluids from individual boars: A set of temporal samples from day 7 to
day 21 (postinfection or vaccination) of paired oral fluids and serum was
collected from 72 boars and divided into three sets (24 boars per trial).
Two of the sets were infected with type I (D09-012131) or type II strain
(MN-184; GenBank* accession no. AY656992); the third set was vaccinated
with type 2 MLV.3
Sample Set 3 (Figure 4)
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 625 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 new rope for each
collection event.
The IDEXX PRRS OF Ab Test detects PRRS antibodies in ≥96% of all
collection events in pens of at least 20% prevalence, and ≥85% in pens of
12% prevalence.
Sample Set 4 (Figure 5)
Oral fluids from individual field samples: Diagnostic specificity and sensitivity
were established with a sample set of paired oral fluids and serum comprised
of 147 samples from a PRRS-positive farm and 151 samples from a
PRRS-negative sow farm, for a total of 298 sets of paired samples.
Figure 3-1 through Figure 3-4. Type I and Type II PRRSV Strains: Antibody Conversion in Serum and Oral Fluids
Figures 3-1 through 3-4 show a selection of pigs individually inoculated with type I and II PRRSV strains, representing the typical conversion of antibodies in both serum
and oral fluids. Analysis indicates little difference between the time of detection of anti-PRRSV antibodies in serum and in oral fluids, as well as a similar ability to detect
antibodies to both type I and II PRRSV strains.
Serum
IDEXX PRRS X3 Ab Test
Oral Fluids
IDEXX PRRS OF Ab Test
Figure 3-1
Sample Set 2
PRRS Type I
1.5
Boar 26
Boar 31
Boar 48
5
S/P
S/P
6
Boar 26
Boar 31
Boar 48
2.0
PRRS Type I
7
2.5
Figure 3-2
Sample Set 2
4
3
1.0
2
0.5
1
0.0
0
0
5
10
Serum
IDEXX PRRS X3 Ab Test
15
0
20
15
20
Figure 3-4
Sample Set 2
PRRS Type II
PRRS Type II
7
2.5
6
Boar 50
Boar 56
Boar 65
2.0
1.5
Boar 50
Boar 56
Boar 65
5
S/P
S/P
10
Oral Fluids
IDEXX PRRS OF Ab Test
Figure 3-3
Sample Set 2
5
4
3
1.0
2
0.5
1
0.0
0
0
5
10
15
20
0
5
10
15
20
DPI (Days Postinfection)
DPI (Days Postinfection)
Cutoff S/P =0.4 (same for oral fluids or serum)
Cutoff S/P =0.4 (same for oral fluids or serum)
Figure 4. Performance Based on Prevalence
Sample Set 3
Prevalence level
(rate of PRRS
antibody-pos
pigs % of pen)
#of pens
Total # of
(# of rope collection collection events
events per pen)
Average serum
S/P of
vaccinated pigs
(from PRRS X3)
Oral fluids: rate of pos events (%)
prevalence level
IDEXX PRRS OF
Ab Test
0
5(5)
25
0
0/25(0%)
4
5(5)
25
1.57
8/25(32%)
12
4(5)
20
1.3
17/20(85%)
20
5(5)
25
1.49
24/25(96%)
32–36
5(5)
25
1.33
24/25(96%)
IDEXX PRRS OF Ab Test
Figure 5. Sensitivity and Specificity
Figure 5 summarizes the performance of the new
PRRS Oral Fluids ELISA compared to results
obtained with the serum-based PRRS X3 assay
on paired samples of oral fluids and serum,
collected from individual commercial sows. The
new PRRS Oral Fluids ELISA had a sensitivity of
100.0% and a specificity of 98.7% (with minimum
sensitivity and specificity of 96.9% and 96.3%,
respectively, at 95% confidence interval).
Commercial Sows
Exposure Status
IDEXX PRRS X3 Ab Test
–
+
Totals
IDEXX PRRS
OF Ab Test
+
147
2
149
–
0
149
149
Totals
147
151
298
95% Confidence Limits
Low CL Sensitivity
Specificity
100.0
98.7
96.9
96.3
High CL
100.0
99.9
Summary
The IDEXX PRRS OF Ab Test accurately
detects PRRS antibodies in oral fluid samples
providing results in less than four hours, using
a non invasive sampling technique.
References:
1.Prickett JR, and Zimmerman JJ. The development of oral fluid-based diagnostics and applications inveterinary
medicine. Anim Health Res Rev. 2010;11(2): 207–216.
2.Kittawornrat A, Prickett J, Wang C, et al. Detection of porcine reproductive and respiratory syndrome virus (PRRSV)
antibodies in oral fluid specimens using a commercial PRRSV serum antibody enzyme-linked immunosorbent assay.
J Vet Diagn Invest. 2012;24(2):262–269.
3.Kittawornrat A, Prickett J, Chittick W, et al. Porcine reproductive and respiratory syndrome virus (PRRSV) in serum
and oral fluid samples from individual boars: will oral fluid replace serum for PRRSV surveillance?
Virus Res. 2010;154(1–2):170–176.
4.Olsen C, Wang C, Christopher-Hennings J, et al. Probability of detecting PRRSV infection using pen-based swine
oral fluid specimens as a function of within-pen prevalence. J Vet Diagn Invest. 2013;Mar 27 (epub).
For more information about the IDEXX PRRS OF Ab Test, please
contact your IDEXX representative or visit idexx.com/prrs.
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registered trademark of the United States Department of Health and Human Services.
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