Guidelines for oral fluid-based surveillance of viral pathogens in swine

Abstract

Recent decades have seen both rapid growth and extensive consolidation in swine production. As a collateral effect, these changes have exacerbated the circulation of viruses and challenged our ability to prevent, control, and/or eliminate impactful swine diseases. Recent pandemic events in human and animal health, e.g., SARS-CoV-2 and African swine fever virus, highlight the fact that clinical observations are too slow and inaccurate to form the basis for effective health management decisions: systematic processes that provide timely, reliable data are required. Oral fluid-based surveillance reflects the adaptation of conventional testing methods to an alternative diagnostic specimen. The routine use of oral fluids in commercial farms for PRRSV and PCV2 surveillance was first proposed in 2008 as an efficient and practical improvement on individual pig sampling. Subsequent research expanded on this initial report to include the detection of ≥23 swine viral pathogens and the implementation of oral fluid-based surveillance in large swine populations (> 12,000 pigs). Herein we compile the current information regarding oral fluid collection methods, testing, and surveillance applications in swine production.

Keywords: ELISA; Oral fluids; RT-PCR; Surveillance; Viral diseases.

Fig. 1

PRRSV antibody kinetics in oral fluid samples collected from 12 pigs vaccinated with a modified-live virus vaccine over the course of 50 days (− 7 to 42 DPV). Reprinted from Rotolo et al. (2018) [40], Veterinary Microbiology 214, 13–20 (copyright 2017) with permission from Elsevier (4812031256013)

Fig. 2

Appearance variability among swine oral fluid samples. a Oral fluids collected under experimental conditions. b Field oral fluids collected from individual-pen held pigs. c-e Field oral fluids collected from pen-held group of pigs

Fig. 3

Probability of PRRSV detection within a barn (~ 1000 pigs) by pen prevalence and number of samples collected. Figure derived from data reported in Rotolo et al. (2017) [90]. Error bars represent the range of detection assuming assay diagnostic sensitivity of 95–100%

Fig. 4

Probability of detecting influenza A virus (IAV) in swine oral fluids by RT-qPCR. Superscripts reflect significant differences (p < 0.05) in assay performance between 13 assays performed in 8 laboratories (A to H). Row groups indicate similar probability detection dose 50 (DD₅₀), that is, the inoculum dilution at which there was a 50% probability of detection (10^–4.68 to 10^–6.68). Reprinted from Goodell et al. (2016) [24] Canadian Journal of Veterinary Research 80, 12–20 (copyright 2016) with permission (#P2020–0011)