Abstract Book of EAVLD2012 - eavld congress 2012

S1 - P - 03
DETECTION OF PRRSV ANTIBODY IN ORAL FLUID SPECIMENS FROM INDIVIDUAL BOARS USING A
COMMERCIAL PRRSV SERUM ANTIBODY ELISA
Apisit Kittawornrat 1 , Mark Engle 3 , John Johnson 1 , John Prickett 1 , Chris Olsen 1 , Trevor Schwartz 1 , Daniel
Whitney 1 , Kent Schwartz 1 , Anna Rice 4 , Andrea Ballagi 4 , Sergio Lizano 4 , Chong Wang 1,2 , Jeffrey Zimmerman 1
1 Department of Veterinary Diagnostic and Production Animal Medicine, 2 Department of Statistics, Iowa State University, 3 PIC North America,
Hendersonville, Tennessee, USA, 4 IDEXX Laboratories, Westbrook, Maine, USA
Oral fluid, Individual boar, ELISA, PRRSV
Introduction
Oral fluid specimens are used in human medicine for the
detection of a variety of infectious agents, hormones, and drugs.
Oral fluid samples are of interest in swine medicine because they
are easily collected, yet highly efficacious for the surveillance of
PRRSV and other pathogens using PCR-based assays (1,3).
Recent work showed that a commercial PRRS serum antibody
ELISA (IDEXX Laboratories, Inc., Westbrook, ME USA) could be
adapted to detect PRRSV antibody in oral fluid specimens (2). In
the current study we describe the kinetics of the ELISAdetectable
anti-PRRSV IgG response in oral fluids collected from
individually-housed boars.
Materials & methods
The study was conducted in 72 boars ranging from 6 months to
3.6 years in age. Boars were under the ownership of PIC North
America (Hendersonville, TN USA) and housing, study
procedures, and protocols were approved and supervised by the
PIC USA Health Assurance and Welfare department.
Boars were assigned to three trials (I, II, III). Boars (n = 24) in
Trial I were intramuscularly (IM) inoculated with 2 ml of a
modified live virus (MLV) vaccine (RespPRRS®, Boehringer
Ingelheim Vetmedica, Inc., St. Joseph, MO USA). Boars (n = 22)
in Trial II were IM inoculated with 2 ml of a Type 1 PRRSV field
isolate. Boars (n = 24) in Trial III were IM inoculated with 2 ml of a
PRRSV Type 2 isolate (MN-184).
Boars were monitored for 21 days post inoculation (DPI). Oral
fluid samples were collected daily using 5/8" 3-strand 100%
cotton rope. Serum samples were collected from all boars on DPI
-7, 0, 7, 14, 21 and from 4 randomly selected boars on DPIs 3, 5,
10, and 17. Thereafter, serum and oral fluid were assayed for
PRRSV antibody using the ELISA protocol appropriate for each
sample type (serum or oral fluid).
Results
The ELISA S/P response in oral fluid and serum samples
followed similar patterns over time (Figure 1). Individual boar oral
fluid samples were ELISA positive from DPI 8 to DPI 21 (Table
1). Overall, 96% of the results were in agreement, i.e., 145 oral
fluid samples and 150 serum samples were ELISA positive.
Table 1: Detection of PRRSV antibody in oral fluid samples from
individually housed boars
PRRSV
ELISA-positive boars (%) by day post inoculation
0 8 9 10 11 12 13 14 17 & 21
MLV 0 0 38 71 88 96 100 100 100
Type 1 0 17 42 59 82 82 81 85 100
Type 2 0 17 65 83 96 96 100 100 100
Total 0 11 48 71 89 91 91 93 100
Discussion & conclusions
The ring test results showed that the PRRS oral fluid IgG ELISA
was highly reproducible across laboratories. These results
support the routine use of this test in laboratories providing
diagnostic service to pig producers. Thus, herd monitoring based
on oral fluid sampling could be one part of a PRRSV control
and/or elimination program. Further, the successful adaptation of
one assay to the oral fluid matrix suggests that this approach
could provide the basis for monitoring specific health and welfare
indicators in commercial swine herds using a "pig friendly"
approach.
References
1. Kittawornrat A, et al. 2010. PRRSV in serum and oral fluid samples from
individual boars. Virus Res 154:170-176.
2. Kittawornrat A, et al. 2012. Detection of PRRSV antibodies in oral fluid
specimens using a commercial PRRSV serum antibody ELISA. J Vet
Diagn Invest 24(2):262-269.
3. Ramirez et al. 2012. Efficient surveillance of pig populations using oral
fluids. Prev Vet Med (Epub ahead of print).
Figure 1: Mean PRRS antibody ELISA kinetics over time: ora
fluid vs. serum samples