Comparison of serum and oral fluid antibody responses after vaccination with a modified live (MLV) porcine reproductive and respiratory syndrome virus (PPRSV) vaccine in PRRS endemic farms

Abstract

Porcine reproductive and respiratory syndrome (PRRS) is a disease that is both highly contagious and of great economic importance in Malaysia. Therefore, reliable and improved diagnostic methods are needed to facilitate disease surveillance. This study compared PRRSV antibody responses in oral fluid versus serum samples following PRRS modified live (MLV) vaccination using commercial antibody ELISA kits (IDEXX Laboratories, Inc.). The study involved two pig farms located in Perak and Selangor, Malaysia. Both farms were vaccinated with PRRS MLV 1 month prior to sample collection. Thirty-five animals were used as subjects in each farm. These 35 animals were divided into 7 different categories: gilts, young sows, old sows, and four weaner groups. Oral fluid and serum samples were collected from these animals individually. In addition, pen oral fluid samples were collected from weaner groups. The oral fluid and serum samples were tested with IDEXX PRRS Oral Fluid Antibody Test Kit and IDEXX PRRS X3 Antibody Test Kit, respectively. The results were based on sample to positive ratio (S/P ratio of the samples). Results revealed a significant and positive correlation between serum and oral fluid samples for both farm A (p = 0.0001, r = 0.681) and farm B (p = 0.0001, r = 0.601). In general, oral fluids provided higher S/P results than serum, but the patterns of response were highly similar, especially for the sow groups. Thus, the use of oral fluids in endemic farms is effective and economical, particularly for large herds. In conclusion, the authors strongly recommend the use of oral fluids for PRRS monitoring in endemic farms.

Keywords: IDEXX PRRS X3 test kit; IDEXX PRRS oral fluid test kit; Oral fluid; Porcine reproductive and respiratory syndrome (PRRS).

Fig. 1

Average S/P ratio for oral fluid and serum samples of farm A sow herds based on IDEXX PRRS OF Ab test and IDEXX PRRS X3 Ab test results, respectively. The values of S/P ratio show the same trend for both oral fluid and serum samples

Fig. 2

Average S/P ratio for oral fluid and serum samples of farm A porkers based on IDEXX PRRS OF Ab test and IDEXX PRRS X3 Ab test results, respectively. The values of S/P ratio show similar trend for both types of samples of all age groups in general except for porkers at 15 weeks which shows that individual oral fluid samples have sharp increase trend compared to serum samples

Fig. 3

Correlation between S/P ratios for oral fluid and serum samples from individual subjects in farm A as a summary statistic (Pearson’s correlation coefficient, r = 0.681)

Fig. 4

Average S/P ratio for oral fluid and serum samples of farm B sow herds based on IDEXX PRRS OF Ab test and IDEXX PRRS X3 Ab test results, respectively. The values of S/P ratio show the same trend for both oral fluid and serum samples

Fig. 5

Average S/P ratio for oral fluid and serum samples of farm A porkers based on IDEXX PRRS OF Ab test and IDEXX PRRS X3 Ab test results respectively. The values of S/P ratio show inconsistent trend regardless oral fluid or serum samples

Fig. 6

Correlation between S/P ratios for oral fluid and serum samples from individual subjects in farm B as a summary statistic (Pearson’s correlation coefficient, r = 0.601)

Fig. 7

Average S/P ratio for oral fluid and serum samples of farm A and farm B sow herds based on IDEXX PRRS OF Ab test and IDEXX PRRS X3 Ab test results, respectively. The values of S/P ratio show similar pattern for both samples

Fig. 8

Average S/P ratio for oral fluid and serum samples of farm A and farm B at different age groups based on IDEXX PRRS OF Ab test and IDEXX PRRS X3 Ab test results, respectively. The values of average S/P ratio of individual oral fluid and serum samples show similar pattern at different age groups. Meanwhile, average S/P ratios for pen oral fluid samples do not deviate much at different age groups

Fig. 9

Correlation between S/P ratios for oral fluid and serum samples from individual subjects in both farms as a summary statistic (Pearson’s correlation coefficient, r = 0.638)