PRRSV RNA Detection and Predictive Values Between Different Sow and Neonatal Litter Sample Types.

Area of Science:

• Veterinary Virology
• Swine Disease Diagnostics
• Animal Reproduction

Background:

• Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) poses significant economic threats to the swine industry.
• Current diagnostic methods struggle to differentiate vertical from horizontal PRRSV transmission or accurately reflect sow status.
• Effective PRRSV diagnostics are crucial for herd management and disease control.

Purpose of the Study:

• To evaluate Tonsil-oral-scrubbing (TOSc) as a diagnostic tool for PRRSV RNA detection in sows.
• To compare PRRSV RNA detection rates between sow TOSc samples and various neonatal litter sample types.
• To assess the predictive values of sow TOSc for determining litter PRRSV status and inferring transmission routes.

Main Methods:

• Collected pre-farrowing TOSc samples from 555 sows around 90 days post-live-virus inoculation (LVI).
• Selected 59 PRRSV-positive and 88 PRRSV-negative sows for further analysis.
• Collected TOSc, live piglet blood swabs, and dead piglet tongue fluid (TF) and serum within 12 hours post-farrowing.

Main Results:

• Pre-farrowing TOSc samples showed significantly higher PRRSV RNA positivity compared to litter samples (TF, serum, blood swabs).
• Dead piglet serum exhibited lower mean Ct values than other sample types.
• Sow TOSc demonstrated a 25% positive predictive value (PPV) and high negative predictive values (NPV) of 87.2% (pre-farrow) and 89.0% (post-farrow) for litter PRRSV status.

Conclusions:

• TOSc is a practical method for detecting PRRSV RNA in sows and neonatal piglets.
• High NPV of sow TOSc suggests its utility in ruling out litter PRRSV infection.
• Findings support the occurrence of vertical PRRSV transmission in sows approximately 90 days post-LVI.