Detection of PRRSV circulation using oral fluid samples for nursery management in endemically PRRSV-infected farms

Abstract

Porcine reproductive and respiratory syndrome (PRRS) has become a major swine disease worldwide. Relevant management strategies and diagnostic assays are of importance for PRRS virus (PRRSV) control. The objective of this study was to determine the use of oral fluids for PRRSV monitoring in endemically PRRSV-infected herds. PRRSV RNA and PRRSV-specific antibodies were monitored using oral fluid samples and serum samples in two conventional swine farms in Thailand ('Farm A', a one-site conventional system farm, and 'Farm B', a one-site P0-P1 segregation system farm) during farrowing to nursery periods. Both PRRSV RNA and PRRSV antibodies were detected from 3 to 9 weeks of age in both sample types. Pen-based oral fluid samples were detected positive over 71% when the prevalence of serum PRRSV-positive pigs in the pens was at least 40%. Mean S/P ratios of the oral fluid samples showed significantly higher levels but had similar pattern to the seroprofile of the blood samples. Increased levels of PRRSV antibodies were detected in all groups at 5 to 9 weeks of age. Overall, the positive correlation of both sample types was 0.65 (p < 0.001). It should be noted that Farm B had higher production losses in the farrowing and nursery units, concurrently, with higher levels of PRRSV load in both sample types. Oral fluid testing provides convenient and economical approach, better welfare, and satisfied performance to determine PRRS status, especially during nursery period, when there is moderate to high PRRSV prevalence. These objectives could be better achieved and benefit practitioners by using oral fluid testing together with other measurements.