Porcine reproductive and respiratory syndrome virus (PRRSV) in serum and oral fluid samples from individual boars: Will oral fluid replace serum for PRRSV surveillance?

Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
Virus Research (Impact Factor: 2.32). 12/2010; 154(1-2):170-6. DOI: 10.1016/j.virusres.2010.07.025
Source: PubMed


The purpose of this study was to determine whether oral fluid samples could be used to monitor individually-housed adult boars for porcine reproductive and respiratory syndrome virus (PRRSV) infection. In 3 trials, 24 boars were intramuscularly (IM) inoculated with a modified-live PRRSV (MLV) vaccine (Trial 1), a Type 1 PRRSV isolate (Trial 2), or a Type 2 isolate (Trial 3). Oral fluid samples were collected daily and serum samples were collected twice weekly. Following the completion of the study, samples were randomized and blind-tested for PRRSV by real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR). PRRSV was detected in oral fluids at DPI 1 and all oral fluid specimens were PRRSV qRT-PCR positive at DPI 4. Although PRRSV was detected in both serum and oral fluid specimens through DPI 21, a comparison of matched samples from individual boars showed that oral fluid was equal to serum for the detection of PRRSV at DPI 7 and more likely to be positive than serum on DPI 14 and 21. Overall, oral fluid was superior to serum for the detection of PRRSV using PCR over the 21-day observation period in this study. The results of this experiment suggest that individually-penned oral fluid sampling could be an efficient, cost-effective approach to PRRSV surveillance in boar studs and other swine populations.

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Available from: Chris W Olsen, May 29, 2014
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    • "PRRSV was first reported in oral fluid in 1997 [21]. Recently, oral fluid sampling has been used to examine swine populations [12,14,15]. There are several situations in which oral fluid sampling may be advantageous for a breeding herd since this method can be performed more frequently at any time during gestation without jeopardizing the welfare of the animals. "
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    ABSTRACT: The objectives of the present study were to investigate the anatomic localization of porcine reproductive and respiratory syndrome virus (PRRSV), and to determine whether oral fluid could be used for the detection of PRRSV in naturally infected pigs in a breeding herd. Two sows that had aborted, seven two-month-old grower pigs and seventy six-month-old gilts were used in this study. PRRSV in sera and oral fluid were assayed by nested reverse transcription polymerase chain reaction (nRT-PCR), tissues sample were tested by nRT-PCR, immunohistochemistry (IHC) and in situ hybridization (ISH). In aborted sows, PRRSV was identified in the oral fluid and tonsils. PRRSV was detected in oral fluid, tonsils, salivary glands, oral mucosa and lungs of all seven grower pigs. However, viremia was detected in only two grower pigs. Double staining revealed that PRRSV was distributed in macrophages within and adjacent to the tonsillar crypt epithelium. In gilts, North American (NA) type PRRSV field strain was detected at 3 to 8 weeks after introduction onto the farm. These results confirm previous findings that in sows, PRRSV primarily replicates in tonsils, and is then shed into oral fluid. Oral fluid sampling may therefore be effective for PRRSV surveillance in breeding herds.
    Journal of veterinary science (Suwŏn-si, Korea) 04/2014; 15(3). DOI:10.4142/jvs.2014.15.3.361 · 1.16 Impact Factor
    • "The oral fluid collection procedure has been fully described by Kittawornrat et al. (2010). In brief, oral fluid samples were collected in the morning (when piglets were active) by suspending 1.25 cm (0.5 in.) unbleached cotton rope (Web Rigging Supply, Inc., Lake Barrington, IL, USA) over the heat mat area, thereby providing access to the piglets, but not the sow. "
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    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.
    Veterinary Microbiology 12/2013; 168(2-4). DOI:10.1016/j.vetmic.2013.11.035 · 2.51 Impact Factor
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    • "As an alternative, pen-based OF are easily collected and the probability of detecting IAV infection by rRT-PCR was actually shown to be higher than individual pig NS specimens in this study and elsewhere (Romagosa et al., 2012). Previously, shown to be an effective diagnostic specimen for a variety of swine pathogens (Detmer et al., 2011; Kittawornrat et al., 2010; Prickett et al., 2008a,b; Ramirez et al., 2012), OF would appear to be the specimen of choice for the surveillance of IAV. "
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    ABSTRACT: The probability of detecting influenza A virus (IAV) by virus isolation (VI), point-of-care (POC) antigen detection, and real-time reverse-transcription polymerase chain reaction (rRT-PCR) was estimated for pen-based oral fluid (OF) and individual pig nasal swab (NS) specimens. Piglets (n=82) were isolated for 30 days and confirmed negative for porcine reproductive and respiratory syndrome virus, Mycoplasma hyopneumoniae, and IAV infections. A subset (n=28) was vaccinated on day post inoculation (DPI) -42 and -21 with a commercial multivalent vaccine. On DPI 0, pigs were intratracheally inoculated with contemporary isolates of H1N1 (n=35) or H3N2 (n=35) or served as negative controls (n=12). OF (n=370) was collected DPI 0-16 and NS (n=924) DPI 0-6, 8, 10, 12, 14, 16. The association between IAV detection and variables of interest (specimen, virus subtype, assay, vaccination status, and DPI) was analyzed by mixed-effect repeated measures logistic regression and the results used to calculate the probability (pˆ) of detecting IAV in OF and NS over DPI by assay. Vaccination (p-value<0.0001), DPI (p-value<0.0001), and specimen-assay interaction (p-value<0.0001) were significant to IAV detection, but virus subtype was not (p-value=0.89). Vaccination and/or increasing DPI reduced pˆ for all assays. VI was more successful using NS than OF, but both VI and POC were generally unsuccessful after DPI 6. Overall, rRT-PCR on OF specimens provided the highest pˆ for the most DPIs, yet significantly different results were observed between the two laboratories independently performing rRT-PCR testing.
    Veterinary Microbiology 07/2013; 166(3-4). DOI:10.1016/j.vetmic.2013.06.029 · 2.51 Impact Factor
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