A severe PRDC challenge and the effect of a trivalent PRDC vaccine for PCV2, Mhp and PRRS

The purpose of this controlled-experimental study was to evaluate pigs vaccinated with 3FLEX® (a trivalent PCV2, Mhp and PRRS vaccine) compared to a non-vaccinated group following a severe PRDC challenge.

03-05-2017


Article by:

P. Philips1, E. Fano1, E. Schmaling2, R. Edler2

1 Boehringer Ingelheim Vetmedica, Inc., MO, USA; 2 Health Management Center (HMC), Field Research Services, BIVI, Ames, Iowa

Introduction

Porcine respiratory disease complex (PRDC) is a significant challenge for the global swine industry. PRDC includes both viral and bacterial respiratory pathogens, mainly Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), Porcine Circovirus type 2 (PCV2), Mycoplasma hyopneumoniae (Mhp) and secondary bacterial agents. Vaccine derived immune protection against clinical disease associated with PRDC pathogens is one control intervention. The purpose of this controlled-experimental study was to evaluate pigs vaccinated with 3FLEX® (a trivalent PCV2, Mhp and PRRS vaccine) compared to a non-vaccinated group following a severe PRDC challenge.

Materials and methods

Group 1 was a non-vaccinated challenged control group of 20 pigs. Group 2 was a 3FLEX® vaccinated and challenged group of 20 pigs. Groups 1 and 2 were simultaneously inoculated with PCV2d (intranasal and intramuscular), Mhp strain 232 (intra tracheal) and PRRSV strain SDSU-73 (intranasal and intramuscular). The challenge incorporates a well referenced virulent heterologous PRRSV isolate, a contemporary virulent PCV2 field isolate, given simultaneously with Mhp, representing a severe PRDC challenge.

Results

Significant differences (P < 0.05) in respiratory clinical signs, gross lung lesions and PCV2 parameters (Lymphoid depletion, IHC and Viremia) are shown in Tables 1, 2 and 3. A reduction in post-challenge PRRSV viremia (Figure 1), and increased average daily weight gain was demonstrated (Table 4) in vaccinates compared to non-vaccinates. Based on clinical, pathological and production results from this study a severe PRDC challenge was successfully accomplished.

Discussion and conclusion

The results of this trial demonstrate that 3FLEX® provides protection to pigs simultaneously challenged with PRRS, PCV2 and Mhp. In the face of severe PRDC challenge, use of a trivalent vaccine mixture is an option for mitigation of the biologic impact of PRDC.

Table 1: Post-challenge clinical observations

Clinical Observation

 

Treatment

P-value

 

Challenge Control

3FLEX®

 

Respiratory

268/530 (50,57%)

205/559 (36,67%)

< 0.0001

Behavior

217/530 (40,94%)

49/559 (8,77%)

< 0.0001

 

Analyzed using Pearson's chi-square

Table 2: Least square means for affected lung percentage by treatment

Treatment Group

Mean

SD

SE

Lower 95%

Upper 95 %

Challenge Control

43.21a

16.87

3.29

36.55

49.87

3FLEX®

22.81b

12.19

3.29

16.15

29.47

ab Means Differ < 0.05 Wilcoxon rank sums test

Table 3: Summary inferential statistics for PCV2 variables.Improvement compared to challenge controls

Variable

Reduction compared to challenge control

P-Value

Tonsil Depletion

Yes

0.073

LN Depletion

Yes

0.038

Tonsil IHC

Yes

0.000

LN IHC

Yes

0.001

Lung IHC

Yes

0.01

Viremia %

Yes

0.01

Viremia CT

Yes

0.00001

Table 4: Summary descriptive statistics for growth performance from day 28 (challenge) to 56 (end of the study). Average Daily Gain, lbs.

Table 4: Summary descriptive statistics for growth performance from day 28 (challenge) to 56 (end of the study). Average Daily Gain, lbs.

Figure 1: Percentage positive and average CT for PRRS PCR results.

Figure 1: Percentage positive and average CT for PRRS PCR results

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