PRRS virus (PRRSV) is a RNA virus with high genetic variation, according to Chao-Nan Lin and colleagues at Taiwan's National Pingtung University of Science and Technology.

In a paper in BMC Veterinary Research, the researchers continue that the virus causes significant economic losses in most pig-producing countries. The clinical presentation of PRRSV ranges from asymptomatic to devastating.

In their study, they developed a sensitive and specific zip nucleic acid probe-based real-time PCR assay to evaluate the viraemia of natural PRRSV-infected pigs in Taiwan.

Serum samples were collected from 577 pigs aged between five and 12 weeks. These include 444 clinically healthy pigs and 133 symptomatic pigs were confirmed to have porcine respiratory disease complex (PRDC).

Viraemia was quantified in 79 of the 444 (17.8 per cent) clinically healthy pigs and in 112 of the 133 (84.2 per cent) PRDC cases.

Viraemia was significantly more common in pigs with PRDC than the clinically healthy pigs (P<0.0001). These results suggest that a high viral load is a major feature of PRRSV-affected pigs.

Lin and colleagues concluded that ZNA probe-based real-time PCR can be a useful tool to diagnose symptomatic and asymptomatic PRRSV-infected pigs. The presence of this marker in a sample of animals with high PRRSV loads (more than 104.2 PRRSV genomes per μl of serum) seems to indicate that it correlates with the presence of PRDC in pigs.

Reference

^{Lin C-N., W-H. Lin, L-N. Hung, S-Y. Wang and M-T. Chiou. 2013. Comparison of viremia of type II porcine reproductive and respiratory syndrome virus in naturally infected pigs by zip nucleic acid probe-based real-time PCR. BMC Veterinary Research. 9:181. doi:10.1186/1746-6148-9-181}

October 2013