Tongue fluids or oral fluids: what do they detect in growing pigs?

Problem: Oral fluids are widely used to monitor PRRSV and influenza A virus (IAV) after weaning, but complementary practical and low-cost methods could strengthen surveillance.

Methods: Three growing-pig herds were followed weekly from placement to market, comparing RT-qPCR results from oral fluids collected in six pens with tongue fluids from mortalities, with additional analyses of mortality, PRRSV ORF5 sequencing, pooling and diagnostic performance.

Takeaway 1: Across 43 matched weeks, PRRSV was detected in 67.4% of oral-fluid samples versus 53.5% of tongue-fluid samples; for IAV, detection was 34.9% versus 30.2%.

Takeaway 2: Despite lower PRRSV detection frequency, positive tongue fluids had a significantly lower mean Ct than oral fluids (29.13 vs 32.8; p=0.0012); among 22 positive pairs submitted for sequencing, success was 63.6% for tongue fluids versus 45.5% for oral fluids.

Takeaway 3: Tongue fluids are best considered a complementary or alternative tool when mortalities are available rather than a systematic replacement for oral fluids; PRRSV detection was also associated with higher weekly mortality in these herds.