Faster, better, cheaper (PRRSV) surveillance using oral fluid-based sampling

1. Faster, better, cheaper (PRRSV) surveillance using oral fluid-based sampling Jeff Zimmerman DVM PhD Iowa State University Ames, Iowa

2. Basic assumptions • We need better surveillance of pathogens of swine, but current methods provide inadequate detection, are unacceptable to farmers, or are too expensive to implement • Good oral fluid antibody and PCR assays can be developed for a variety of pathogens • How well would these assays work?

3. Performance of oral fluids in PRRSV surveillance - a field study C Olsen,1C Wang,1 J Christopher-Hennings,2 K Doolittle,3 K Harmon,1 S Abate,1 A Kittawornrat,1 S Lizano,5 R Main,1 E Nelson,2 T Otterson,6 Y Panyasing,1 C Rademacher,4 R Rauh,7 R Shah,8 J Zimmerman1 1Iowa State University, 2South Dakota State University, 3Boehringer IngelheimVetmedica, Inc., 4Murphy-Brown LLC, 5IDEXX Laboratories Inc., 6University of Minnesota, 7Tetracore®, Inc., 8Life Technologies®, Inc.

4. Objective - Estimate the probability of detecting PRRSV infection as a function of within-pen prevalence

5. Experimental design • 25 pens, 25 pigs per pen • Prevalence was established using pigs vaccinated with PRRSV MLV vaccine

6. PRRSV MLV SITE 1 SITE 2 … 14 DPV - serum antibody and virus positive 25 pigs per pen

7. Experimental design ● DPV 0 PRRSV-negative pigs (n = 90) in Missouri vaccinated with MLV PRRSV MLV. ● DPV 10 PRRSV-vaccinated pigs (n = 90) in Missouri brought to Iowa farm and placed in isolation ● DPV 12 PRRSV-negative pigs (n = 535) from Oklahoma brought to Iowa farm, placed in 25 pens, oral fluid collected from each pen. ● DPV 13 Morning: blood sample from each of 535 negative pigs. Afternoon: Within pen PRRSV prevalence (0%, 4%, 12%, 20%, or 36%) established by placing 0, 1, 3, 5, or 9 PRRSV-vaccinated pigs in the 25 pens. Each pen held a total of 25 pigs after placement. ● DPV 14 5 successive oral fluid samples were collected from each pen, i.e., a total of 125 samples. ● DPV 14 Serum samples were collected from each of the 90 vaccinated pigs to establish PRRSV status.

8. Probability of detection as a function of prevalence?

9. PRRSV RT-PCR results on oral fluids

10. PRRSV RT-PCR results on oral fluids *n = number of oral fluid samples

11. PRRSV ELISAresults on oral fluids

12. PRRSV ELISA results on oral fluids *n = number of oral fluid samples

13. COMPARISON

14. One oral fluid sample One serum sample X x x Within-pen prevalence

15. Increased probability of PRRSV detection with one oral fluid samples vs. one serum sample X x x Within-pen prevalence

16. Conclusions • Oral fluid-based detection of PRRSV infection using either ELISA or RT-PCR is effective, efficient, and easy. • The estimates in this study are conservative: 1. Vaccine-induced viremia and antibody response is "weaker" than natural infection (Johnson et al., 2004) 2. Vaccinated pigs were introduced into pens ~16 hours prior to collection. Lack of socialization adversely affects sampling behavior. 3. Results from all laboratories were included in the estimates. 4. Oral fluid-based surveillance could facilitate faster, better, cheaper surveillance of PRRSV and other pathogens

17. Thank you! jjzimm@iastate.edu