Surveillance using pre-weaning oral fluid samples detects wild-type PRRSv

Kittawornrat A¹, Panyasing Y², Goodell C³, Wang C⁴, Gauger P¹, Harmon K¹, Rauh R⁵, Desfresne L⁶, Levis I⁶, Zimmerman J⁷. Porcine reproductive and respiratory syndrome virus (PRRSV) surveillance using pre-weaning oral fluid samples detects circulation of wild-type PRRSV. Vet Microbiol. 2014 Jan 31;168(2-4):331-9. doi: 10.1016/j.vetmic.2013.11.035. Epub 2013 Dec 14.

¹Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA. ²Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA; Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand. ³IDEXX Laboratories, Inc., Westbrook, ME 04092, USA. ⁴Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA; Department of Statistics, College of Liberal Arts and Sciences, Iowa State University, Ames, IA 50011, USA. ⁵Tetracore(®), Inc., Rockville, MD 20850, USA. ⁶Seaboard Farms, Inc., Guymon, OK 73942, USA. ⁷Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA. Electronic address: jjzimm@iastate.edu.

Abstract

Oral fluid samples collected from litters of piglets (n=600) one day prior to weaning were evaluated as a method to surveil for porcine reproductive and respiratory syndrome virus (PRRSV) infections in four sow herds of approximately 12,500 sow each. Serum samples from the litters' dam (n=600) were included for comparison. All four herds were endemically infected with PRRSV and all sows had been vaccinated ≥ 2 times with PRRSV modified-live virus vaccines. After all specimens had been collected, samples were randomized and assayed by PRRSV real-time reverse transcription polymerase chain reaction (RT-qPCR) and four PRRSV antibody ELISA assays (IgM, IgA, IgG, and Commercial Kit). All sow serum samples were negative by PRRSV RT-qPCR, but 9 of 600 oral fluid samples tested positive at two laboratories. Open reading frame 5 (ORF5) sequencing of 2 of the 9 positive oral fluid samples identified wild-type viruses as the source of the infection. A comparison of antibody responses in RT-qPCR positive vs. negative oral fluid samples showed significantly higher IgG S/P ratios in RT-qPCR-positive oral fluid samples (mean S/P 3.46 vs. 2.36; p=0.02). Likewise, sow serum samples from RT-qPCR-positive litter oral fluid samples showed significantly higher serum IgG (mean S/P 1.73 vs. 0.98; p<0.001) and Commercial Kit (mean S/P 1.97 vs. 0.98; p<0.001) S/P ratios. Overall, the study showed that pre-weaning litter oral fluid samples could provide an efficient and sensitive approach to surveil for PRRSV in infected, vaccinated, or presumed-negative pig breeding herds.

Copyright © 2014 Elsevier B.V. All rights reserved.

KEYWORDS:

Oral fluid antibody; PRRSV; RT-qPCR; Surveillance

PMID: 24393634 [PubMed - indexed for MEDLINE]