Comparison of serum pools and oral fluid samples for detection of porcine circovirus type 2 by quantitative real-time PCR in finisher pigs

Research output: Contribution to journalJournal article – Annual report year: 2018Researchpeer-review

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  • Author: Nielsen, Gitte Blach

    MSD Animal Health Nordic, Denmark

  • Author: Nielsen, Jens Peter

    University of Copenhagen, Denmark

  • Author: Haugegaard, John

    MSD Animal Health Nordic, Denmark

  • Author: Leth, Sanne Christiansen

    Porcus ApS, Denmark

  • Author: Larsen, Lars E

    Virology, Division for Diagnostics & Scientific Advice, National Veterinary Institute, Technical University of Denmark, Kemitorvet, 2800, Kgs. Lyngby, Denmark

  • Author: Kristensen, Charlotte Sonne

    SEGES Pig Research Center, Denmark

  • Author: Pedersen, Ken Steen

    OE-Vet, Denmark

  • Author: Stege, Helle

    University of Copenhagen, Denmark

  • Author: Hjulsager, Charlotte K.

    SEGES Pig Research Center, Denmark

  • Author: Houe, Hans

    University of Copenhagen, Denmark

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Porcine circovirus type 2 (PCV2) diagnostics in live pigs often involves pooled serum and/or oral fluid samples for group-level determination of viral load by quantitative real-time polymerase chain reaction (qPCR). The purpose of the study was to compare the PCV2 viral load determined by qPCR of paired samples at the pen level of pools of sera (SP) from 4 to 5 pigs and the collective oral fluid (OF) from around 30 pigs corresponding to one rope put in the same pen. Pigs in pens of 2 finishing herds were sampled by cross-sectional (Herd 1) and cross-sectional with follow-up (Herd 2) study designs. In Herd 1, 50 sample pairs consisting of SP from 4 to 5 pigs and OF from around 23 pigs were collected. In Herd 2, 65 sample pairs consisting of 4 (SP) and around 30 (OF) pigs were collected 4 times at 3-week intervals. A higher proportion of PCV2-positive pens (86% vs. 80% and 100% vs. 91%) and higher viral loads (mean difference: 2.10 and 1.83 log(10) PCV2 copies per ml) were found in OF versus SP in both herds. The OF cut-off value corresponding to a positive SP (>3 log(10) PCV2 copies per ml) was estimated to 6.5 and 7.36 log(10) PCV2 copies per ml for Herds 1 and 2, respectively. Significant correlations between SP and OF results were found in Herd 1 (rho = 0.69) and the first sampling in Herd 2 (rho = 0.39), but not for the subsequent consecutive 3 samplings in Herd 2. The proportion and viral loads of PCV2 positive pens were higher in collective OF (including up to 30 pigs) compared to SP (including 4-5 pigs) of the same pens. Also, OF seemed to detect the PCV2 infection earlier with OF values just below 6.5 (Herd 1) and 7.36 (Herd 2) log(10) being associated with a negative SP for the same pen. Nevertheless, a statistically significant correlation between SP and OF could not be found for all sampling time points, probably due to a high within-pen variation in individual pig viral load becoming very evident in SP of only four or five pigs. Consequently, the results imply that OF is well suited for detecting presence of PCV2 but less so for determining the specific viral load of pigs in a pen.
Original languageEnglish
JournalPorcine Health Management
Volume4
Issue number2
Number of pages10
ISSN2055-5660
DOIs
Publication statusPublished - 2018

Bibliographical note

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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    Research areas

  • Diagnostics, Finishers, Oral fluid, Pooling, Porcine circovirus type 2, Serum

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