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Nielsen GB, Nielsen JP, Haugegaard J, et al. Comparison of serum pools and oral fluid samples for detection of porcine circovirus type 2 by quantitative real-time PCR in finisher pigs. Porcine Health Manag. 2018;4:2doi: 10.1186/s40813-018-0079-4.
Nielsen, G. B., Nielsen, J. P., Haugegaard, J., Leth, S. C., Larsen, L. E., Kristensen, C. S., Pedersen, K. S., Stege, H., Hjulsager, C. K., & Houe, H. (2018). Comparison of serum pools and oral fluid samples for detection of porcine circovirus type 2 by quantitative real-time PCR in finisher pigs. Porcine health management, 42. https://doi.org/10.1186/s40813-018-0079-4
Nielsen, Gitte Blach, et al. "Comparison of serum pools and oral fluid samples for detection of porcine circovirus type 2 by quantitative real-time PCR in finisher pigs." Porcine health management vol. 4 (2018): 2. doi: https://doi.org/10.1186/s40813-018-0079-4
Nielsen GB, Nielsen JP, Haugegaard J, Leth SC, Larsen LE, Kristensen CS, Pedersen KS, Stege H, Hjulsager CK, Houe H. Comparison of serum pools and oral fluid samples for detection of porcine circovirus type 2 by quantitative real-time PCR in finisher pigs. Porcine Health Manag. 2018 Feb 01;4:2. doi: 10.1186/s40813-018-0079-4. eCollection 2018. PMID: 29435356; PMCID: PMC5793352.
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Porcine Health Manag. 2018 Feb 01;4:2. doi: 10.1186/s40813-018-0079-4. eCollection 2018.

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

Porcine health management

Gitte Blach Nielsen, Jens Peter Nielsen, John Haugegaard, Sanne Christiansen Leth, Lars E Larsen, Charlotte Sonne Kristensen, Ken Steen Pedersen, Helle Stege, Charlotte K Hjulsager, Hans Houe

Affiliations

  1. MSD Animal Health Nordic, Havneholmen 25, 1561 Copenhagen V, Denmark.
  2. 2Department of Veterinary and Animal Sciences, University of Copenhagen, Grønnegårdsvej 2+8, 1870 Frederiksberg C, Denmark.
  3. Porcus Veterinary Pig Practice, Ørbækvej 276, 5220 Odense, SØ Denmark.
  4. National Veterinary Institute, Henrik Dams Allé, Bygning 205B, 2800 Kgs. Lyngby, Denmark.
  5. SEGES Pig Research Centre, Vinkelvej 11, 8620 Kjellerup, Denmark.
  6. Ø-vet A/S, Køberupvej 33, 4700 Næstved, Denmark.

PMID: 29435356 PMCID: PMC5793352 DOI: 10.1186/s40813-018-0079-4

Abstract

BACKGROUND: 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.

RESULTS: 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.

CONCLUSIONS: 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.

Keywords: Diagnostics; Finishers; Oral fluid; Pooling; Porcine circovirus type 2; Serum

Conflict of interest statement

Permission to conduct the field trial in Herd 2 was received from the Danish Health and Medicines Authority (License no. 2014022507) and a written consent was obtained from the herd owner.Not applicab

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