Abstract Book of EAVLD2012 - eavld congress 2012

S1 - O - 2
DIAGNOSTIC PROPERTIES OF SEVERAL PRRS ANTIBODY ELISAS IN THE CONTEXT OF A
LONGITUDINALSTUDY OF A FARM USING DIFFERENT VACCINATION STRATEGIES
Strutzberg-Minder K 1 , Seidenspinner M 2 , Schuh H 2 , Böttcher J 3 , Wendt M 4 , Leibold W 5
1 IVD GmbH, Hannover, Germany,
2 Dr. Hermann Schuh, Veterinary Practice, Ipsheim, Germany
3 Bavarian Animal Health Service, Poing, Germany,
University of Veterinary Medicine, Foundation, 4 Klinik für kleine Klauentiere, 5 Institute of Immunology, Hannover, Germany
PRRS virus, serology
Introduction
Porcine reproductive and respiratory syndrome (PRRS) is one of
the most important diseases in pig farms almost worldwide (1).
The PRRS virus (PRRSv) causes severe economic losses due to
reproductive failures in sows and gilts and respiratory distress in
piglets and fattening pigs (1). Among the objectives of the study
was a longitudinal analysis of the antibody response following
different vaccination strategies by routine diagnostic ELISA.
Materials & methods
The study was performed on an intensive pig farm in Germany
with about 120 sows, 450 raising sites and 500 fattened pigs in a
closed system. 8 to 12 piglets of 6 sows examined preliminarily
were reassembled in 4 different groups with a total of 15 piglets
in each. Blood samples were taken at 10 weeks (w), 13 w, 16 w,
21 w, 26 w and 27 w of age. Pigs were vaccinated with Porcilis ®
PRRS (live European PRRSV strain DV, Intervet International,
now: MSD Animal Health, USA) and Progressis ®
(inactivated
PRRSv European strain P120, Merial, UK) as described in the
instruction manuals and in the following table.
Table 1: Vaccination schedule
Group 1 Group 2 Group 3 Group 4
Age of pigs
(red)
(blue)
(green) (yellow)
8 Progressis ®
11
Porcilis ® Porcilis ® Porcilis ®
PRRS
PRRS
PRRS
20 Progressis ® Progressis ®
25
Porcilis ® Porcilis ®
PRRS
PRRS
Progressis ®
Porcilis ®
PRRS
Porcilis®
PRRS
Serum samples were analysed with the following PRRS antibody
ELISAs:
A) HerdChek* PRRS 2XR, IDEXX Laboratories, USA. A
sample/positive control (S/P) ratio (blanked by normal host
cells antigen for control) ≥ 0.400 is positive.*
B) HerdChek* PRRS X3 (now: IDEXX PRRS X3), IDEXX
Laboratories, USA. An S/P ratio (blanked by negative
control, NC) ≥ 0.400 is positive.*
C) INGEZIM PRRS UNIVERSAL, INGENASA, Spain. S/P ratio
transformed in OD%; an OD% > 15 is positive.
D) INGEZIM PRRS EUROPA, INGENASA, Spain. S/P ratio
transformed in OD%; an OD% > 15 is positive.
E) INGEZIM PRRS AMERICA, INGENASA, Spain. S/P ratio
transformed in OD%; an OD% > 15 is positive.
F) CIVTEST SUIS PRRS E/S (European strains), Laboratories
HIPRA, Spain. An IRPC (Index Relative to Positive Control)
value ((sample - NC) / (PC - NC) x 100) > 20 is positive.
G) CIVTEST SUIS PRRS A/S (American strains), Laboratories
HIPRA, Spain. IRPC value >20 is positive
H) INGEZIM DR, INGENASA, Spain. S/P ratio transformed in
OD%; an OD% > 17.5 is positive.
I) PRRSv, BioChek, The Netherlands. An OD > 0.500 is
positive.*
*Results of ELISA with real numbers were multiplied by 100 to
yield a positive integer for better comparison of the different
ELISA results in one diagram (Fig. 1). ELISA H and I were used
only for group 2.
Results
The individual course of antibody development detected by all
ELISA differed most in group 4. However, the arithmetic means
smoothed the individual differences (Fig. 1). Results for group 4
were significantly higher (p ≤ 0.0606) than for group 1 and 2 at 13
w. Maximum antibody levels were observed between 21 w and
26 w (10 w to 15 w after priming with Porcilis ® PRRS) for all
ELISA (Fig. 1). These peaks were more or less independent of
subsequent boosting with Progressis ® or with Porcilis ® PRRS (s.
Tab. 1).
Mean of ELISA results
3.500
3.000
2.500
2.000
1.500
1.000
0.500
ELISA B
0.000
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Age of pigs (weeks)
Group 1 Group 2 Group 3 Group 4
Figure 1: Pigs' developing antibody response (mean ELISA
results) with 4 different PRRSv vaccination strategies detectable
by different ELISAs (here: ELISA B) for PRRSv antibodies
The earliest positive results after exposition with live PRRSv
vaccine at 11 w were detected by ELISAs A and B in at least 6
(group 3) of 15 samples and all means of all groups (Fig. 2) at 13
w (2 w after priming with Porcilis ®
PRRS). ELISA H tested
positive in all but 2 samples at all dates before and after
vaccination without significant changes in results (Fig. 2). The
earliest positive results of the other ELISAs C, D, F and I in
almost all samples and all means of groups 1-3 were at 16 w (5 w
after priming with Porcilis ® PRRS) (Fig. 2). Only group 4 tested
positive also by ELISAs C, D and F at 13 w.
Mean of ELISA results
450
Group 2
400
350
300
250
200
150
100
50
0
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Age of pigs (weeks)
ELISA A ELISA B ELISA C ELISA D ELISA F ELISA H ELISA I
Figure 2: Pigs' developing antibody response with different
PRRSv vaccination strategies (here: group 2 mean ELISA
results) detectable by different ELISAs for PRRSv antibodies
Discussion & conclusion
As ELISA H results did not reflect any PRRS vaccination they
were not useful for understanding antibody development as an
immunological response to PRRSv. The earliest detection of
exposing pigs to live PRRSv was possible with ELISA A and B at
the first sampling (2 w after priming). Pre-immunization with
Progressis ® (group 4) also made it possible to detect antibodies
against PRRSv at 13 w by the other positive ELISAs C, D and F,
but individual serological profiles were very heterogeneous, while
all other individual serological profiles (groups 1-3) were more
homogenous and represented appropriately by the group means.
ELISAs A and B can be used at the latest 2 w after priming with
PRRSv for early detection, and other ELISAs except E, G and H,
for monitoring the antibody response.
References
1. Zimmermann et al. (2006) in: Straw et al. (eds.), Diseases of Swine,
9thed., 387-417
Note: These data are in part results of the thesis of Marc Seidenspinner