Field evaluation of two commercial RT-rtPCR assays for porcine reproductive and respiratory syndrome virus detection using sera from ill and healthy pigs, China

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) is a highly contagious respiratory virus causing severe morbidity in pigs worldwide. Control strategies for PRRSV often rely on detecting PRRSV, culling or isolating sick pigs, disinfecting pig barns, vaccination, and monitoring for virus spread. Given the high economic impact of PRRSV on pig farms, there is a great need for rapid and reliable PRRSV detection assays. We compared the performance of 2 commercial reverse-transcription real-time PCR (RT-rtPCR) assays, the VetMAX PRRSV NA and EU reagents (ABI assay) and the PRRSV general RT-rtPCR kit (Anheal assay), for the molecular detection of PRRSV in sera collected from pigs in China. Between June and September 2015, sera were collected from 219 healthy and 104 suspected PRRSV-infected pigs on 4 farms in China. Employing blinding, the 2 assays were run by 2 laboratories (Guangzhou Animal Health Inspection Institute [GAHII] and Sun Yat-sen University [SYSU] laboratories) and compared. Although both assays detected PRRSV with 100% specificity at both laboratories, the sensitivity (95% vs. 78% at GAHII; 94% vs. 72% at SYSU Laboratory) and the reproducibility (kappa value 0.933 vs. 0.931) were slightly better for the ABI assay compared to the Anheal assay.

Keywords: China; detection; porcine reproductive and respiratory syndrome; test evaluation.

Figure 1.

Specimens were collected from 4 farms in Guangdong, Fujian, and He’nan Provinces in China between June and September 2015.

Figure 2.

Sera were collected from suspected porcine reproductive and respiratory syndrome virus (PRRSV)-infected and healthy pigs. Two panels of original sera were created for Sun Yat-sen University (SYSU) and Guangzhou Animal Health Inspection Institute (GAHII) laboratories. SYSU and GAHII laboratorians were blinded with respect to the pigs’ signs of PRRSV infection. Nucleic acid extractions were performed separately by each laboratory. Each laboratory performed both ABI and Anheal RT-rtPCR assays.

Figure 3.

Comparison of cycle threshold (Ct) values from 2 porcine reproductive and respiratory syndrome virus (PRRSV) RT-rtPCR tests at 2 laboratories. “No Ct” indicates that no PCR amplification signal was observed by the endpoint of a test, which was 37 cycles for the Anheal assay or 40 cycles for the ABI assay. Where one of the 2 assays had “No Ct,” the results were plotted on either the x- or the y-axis.