Optimizing Tongue Fluid Sampling and Testing Protocols for Enhanced PRRSV Isolation from Perinatal Swine Mortalities

Area of Science:

• Veterinary Virology
• Swine Disease Diagnostics

Background:

• Porcine reproductive and respiratory syndrome virus (PRRSV) poses significant economic and health challenges to the global swine industry.
• Effective PRRSV isolation is critical for disease surveillance, outbreak investigation, and the development of targeted vaccines and control strategies.

Purpose of the Study:

• To evaluate the efficacy of tongue fluid (TF) collected from perinatal piglet mortalities as a source for PRRSV isolation.
• To compare different TF collection protocols and assess the suitability of various cell lines for PRRSV isolation.

Main Methods:

• Four tongue fluid collection methods were tested: phosphate-buffered saline (PBS), virus transportation medium (VTM), freeze-thaw, and tissue homogenates.
• PRRSV isolation was attempted using two cell lines (ZMAC, MARC-145) and primary alveolar macrophages (PAM).
• RT-qPCR was used to assess viral RNA load, and virus isolation (VI) success rates were determined for each method and cell line.

Main Results:

• The PBS collection protocol demonstrated the highest virus isolation success rate (22.6%), followed by the VTM group (12.1%). Freeze-thaw and homogenate methods showed significantly lower success rates (2.8% each).
• The ZMAC cell line yielded the highest PRRSV isolation rate (21.0%) compared to MARC-145 (3.1%) and PAM cells (4.8%).
• Mean RT-qPCR Ct values were lowest for the PBS and VTM groups, indicating higher viral RNA concentrations.

Conclusions:

• Tongue fluid from perinatal piglet mortalities is a viable alternative sample source for PRRSV virus isolation.
• The PBS collection method combined with the ZMAC cell line appears most effective for maximizing PRRSV isolation from this sample type.
• This approach can support PRRSV monitoring and control efforts in swine populations.