Less invasive sampling methods for PRRSV detection in swine: Dry blood spots, oral swabs, and tonsil oral scrubbing in intentionally exposed gilts

Serum collection from swine is invasive and labor-intensive, which limits its practicality for disease surveillance and highlights the need for less invasive and cost-effective alternatives.

Objective: In this study, we evaluated the sensitivity of blood-soaked filter papers (dry blood spots [DBS]), blood-soaked swabs, oral swabs (OS), and tonsil oral scrubbing (TOSc) when compared to serum for the detection of Porcine Reproductive and Respiratory Syndrome (PRRS) in viremic gilts under field conditions.

Methods and results: Two studies were conducted with 50 recently inoculated gilts each. In study 1, tail pricking DBS and tail blood swabs were collected, with the sensitivity of the latter at 62.5% using serum as a reference. In study 2, PRRS RNA was detected in 100% of serum, TOSc, and DBS samples collected via ear pricking, yielding 100% sensitivity for both TOSc and DBS when compared to serum. However, OS and ear blood swabs showed ~90% sensitivity. Additionally, viral sequencing performed on serum and DBS from one gilt yielded identical sequences. While PRRS genetic material was successfully detected in all assessed specimens, sensitivity varied, with TOSc and ear prick DBS showing the strongest performance compared to serum. In terms of practicality of sample collection, OS ranked highest in ease and speed of collection, followed by TOSc, which required additional preparation time. Cost differences among sampling methods were described, with DBS as the most economical option at $0.44 per sample.

Conclusion: This study supports the use of less invasive sampling methods for PRRS surveillance, particularly TOSc and DBS, which emerged as reliable and cost-effective alternatives for detecting the virus in recently inoculated gilts.