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The use of oral fluids to monitor key pathogens in porcine respiratory disease complex

View Article: PubMed Central - PubMed

ABSTRACT

Background: The usefulness of oral fluid (OF) sampling for surveillance of infections in pig populations is already accepted but its value as a tool to support investigations of porcine respiratory disease complex (PRDC) has been less well studied. This study set out to describe detection patterns of porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), swine influenza virus type A (SIV) and Mycoplasma hyopneumoniae (M. hyo) among farms showing differing severity of PRDC.

Background: The study included six wean-to-finish pig batches from farms with historical occurrence of respiratory disease. OF samples were collected from six pens every two weeks from the 5th to the 21st week of age and tested by real time PCR for presence of PRRSV, SIV and M. hyo and by quantitative real time PCR for PCV2. Data was evaluated alongside clinical and post-mortem observations, mortality rate, slaughter pathology, histopathology, and immunohistochemistry testing data for PCV2 antigen where available.

Results: PRRSV and M. hyo were detectable in OF but with inconsistency between pens at the same sampling time and within pens over sequential sampling times. Detection of SIV in clinical and subclinical cases showed good consistency between pens at the same sampling time point with detection possible for periods of 2–4 weeks. Quantitative testing of OF for PCV2 indicated different patterns and levels of detection between farms unaffected or affected by porcine circovirus diseases (PCVD). There was good correlation of PCR results for multiple samples collected from the same pen but no associations were found between prevalence of positive test results and pen location in the building or sex of pigs.

Conclusions: Detection patterns for PRRSV, SIV and M. hyo supported the effectiveness of OF testing as an additional tool for diagnostic investigation of PRDC but emphasised the importance of sampling from multiple pens and on multiple occasions. Preliminary evidence supported the measurement of PCV2 load in pooled OF as a tool for prediction of clinical or subclinical PCVD at farm level.

No MeSH data available.


PRRSV Ct values in OF samples. Real-time PCR Ct values for PRRSV in OF samples collected from pens at between 5 and 21 weeks of age. Each sample from each rope is represented regarding batch, time point and pen from which it was collected. Samples with positive detection are represented in BLACK (Ct values <37); inconclusive results in RED (Ct values ≥37 and <40); Negative results (no detection in CT ≥ 40) in BLUE
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Fig3: PRRSV Ct values in OF samples. Real-time PCR Ct values for PRRSV in OF samples collected from pens at between 5 and 21 weeks of age. Each sample from each rope is represented regarding batch, time point and pen from which it was collected. Samples with positive detection are represented in BLACK (Ct values <37); inconclusive results in RED (Ct values ≥37 and <40); Negative results (no detection in CT ≥ 40) in BLUE

Mentions: PRRSV nucleic acid was detected only in C1 (7/9 time points) and B2 (3/9 time points) (Fig. 3) with positive results obtained from weaning age onwards in both batches. Maximum pen-level prevalence was 6/6 for C1 but only 2/6 for B2. There was an apparent decline in pen level prevalence at later time-points. Detection patterns were irregular over time in that a pen testing positive on multiple occasions might also report interspersed negative results. All Ct values were higher than 31 indicating low levels of detectable viral RNA in the samples. Serum samples collected at 15 weeks of age were negative for PRRSV PCR for every batch, and positive for PRRSV antibodies in 12/12 pigs tested in each of C1 and B2 but all other batches gave negative results (Table 4).Fig. 3


The use of oral fluids to monitor key pathogens in porcine respiratory disease complex
PRRSV Ct values in OF samples. Real-time PCR Ct values for PRRSV in OF samples collected from pens at between 5 and 21 weeks of age. Each sample from each rope is represented regarding batch, time point and pen from which it was collected. Samples with positive detection are represented in BLACK (Ct values <37); inconclusive results in RED (Ct values ≥37 and <40); Negative results (no detection in CT ≥ 40) in BLUE
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5382517&req=5

Fig3: PRRSV Ct values in OF samples. Real-time PCR Ct values for PRRSV in OF samples collected from pens at between 5 and 21 weeks of age. Each sample from each rope is represented regarding batch, time point and pen from which it was collected. Samples with positive detection are represented in BLACK (Ct values <37); inconclusive results in RED (Ct values ≥37 and <40); Negative results (no detection in CT ≥ 40) in BLUE
Mentions: PRRSV nucleic acid was detected only in C1 (7/9 time points) and B2 (3/9 time points) (Fig. 3) with positive results obtained from weaning age onwards in both batches. Maximum pen-level prevalence was 6/6 for C1 but only 2/6 for B2. There was an apparent decline in pen level prevalence at later time-points. Detection patterns were irregular over time in that a pen testing positive on multiple occasions might also report interspersed negative results. All Ct values were higher than 31 indicating low levels of detectable viral RNA in the samples. Serum samples collected at 15 weeks of age were negative for PRRSV PCR for every batch, and positive for PRRSV antibodies in 12/12 pigs tested in each of C1 and B2 but all other batches gave negative results (Table 4).Fig. 3

View Article: PubMed Central - PubMed

ABSTRACT

Background: The usefulness of oral fluid (OF) sampling for surveillance of infections in pig populations is already accepted but its value as a tool to support investigations of porcine respiratory disease complex (PRDC) has been less well studied. This study set out to describe detection patterns of porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), swine influenza virus type A (SIV) and Mycoplasma hyopneumoniae (M. hyo) among farms showing differing severity of PRDC.

Background: The study included six wean-to-finish pig batches from farms with historical occurrence of respiratory disease. OF samples were collected from six pens every two weeks from the 5th to the 21st week of age and tested by real time PCR for presence of PRRSV, SIV and M. hyo and by quantitative real time PCR for PCV2. Data was evaluated alongside clinical and post-mortem observations, mortality rate, slaughter pathology, histopathology, and immunohistochemistry testing data for PCV2 antigen where available.

Results: PRRSV and M. hyo were detectable in OF but with inconsistency between pens at the same sampling time and within pens over sequential sampling times. Detection of SIV in clinical and subclinical cases showed good consistency between pens at the same sampling time point with detection possible for periods of 2&ndash;4 weeks. Quantitative testing of OF for PCV2 indicated different patterns and levels of detection between farms unaffected or affected by porcine circovirus diseases (PCVD). There was good correlation of PCR results for multiple samples collected from the same pen but no associations were found between prevalence of positive test results and pen location in the building or sex of pigs.

Conclusions: Detection patterns for PRRSV, SIV and M. hyo supported the effectiveness of OF testing as an additional tool for diagnostic investigation of PRDC but emphasised the importance of sampling from multiple pens and on multiple occasions. Preliminary evidence supported the measurement of PCV2 load in pooled OF as a tool for prediction of clinical or subclinical PCVD at farm level.

No MeSH data available.