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Brief Report
Revised

A survey on the occurrence of Brachyspira pilosicoli and Brachyspira hyodysenteriae in growing-finishing pigs

[version 3; peer review: 2 approved, 1 approved with reservations]
PUBLISHED 01 Apr 2021
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Abstract

Background: The major pathogenic intestinal spirochetes affecting pigs during the growing- finishing stage of production include Brachyspira hyodysenteriae and Brachyspira pilosicoli. The aim of this study was to assess the current occurrence of B. hyodysenteriae and B. pilosicoli in Polish pig herds. Moreover, associations between the presence of diarrhea or other intestinal pathogens and occurrence of B. hyodysenteriae and B. pilosicoli in pigs were investigated.
Methods: Between January 2017 and August 2019, a total of 401 samples of pig feces from 95 different herds were submitted to the National Veterinary Research Institute of Poland. These samples were obtained from pigs older than 7 weeks. All the received fecal samples were examined for the presence of B. hyodysenteriae, B. pilosicoli and Lawsonia intracellularis by real-time PCR.
Results: B. pilosicoli was detected in 4.5% (95% CI, 2.5–7.0%) (18/401) of pig fecal samples. At the herd level 13.7% (95% CI, 7.5–22.3%) (13/95) of herds were positive for B. pilosicoli. B. hyodysenteriae was detected in 7.0% (95% CI, 4.7–9.9%) (28/401) of pig fecal samples and 18.9% (95% CI, 11.6–28.3%) (18/95) of pig herds were positive. Out of 18 B. pilosicoli positive samples, this pathogen was detected alone in 5 samples; simultaneously with L. intracellularis in 9 samples; simultaneously with B. hyodysenteriae in 1 sample and in 3 samples was detected simultaneously with both of these bacteria. The presence of B. hyodysenteriae in fecal samples was associated with the presence of diarrhea in pigs.
Conclusions: This study confirmed that B. pilosicoli infections occur in Polish pig herds, but the prevalence is at a low level and the presence of B. pilosicoli is not associated with the development of diarrhea in pigs. B. hyodysenteriae is still a common cause of diarrhea among pigs from Polish herds.

Keywords

Brachyspira pilosicoli, Brachyspira hyodysenteriae, Lawsonia intracellularis, pigs, intestinal pathogens, enterocolitis, diarrhea

Revised Amendments from Version 2

In the sentence "Out of 18 B. pilosicoli positive samples, this pathogen was detected alone in 5 samples" “this” has been replaced with “the”.
 
In the sentence "The subclinical colonization of pigs, with B. pilosicoli is not uncommon and has been detected in several farms." Comma has been removed.
 
In the sentence "The second group was made up of samples (n=70) from pigs with clinical sings." Correction of "sings" to "signs" has been made.
 
The sentence "Besides, B. pilosicoli tests were performed in July and August 2019." has been rephrased.

See the authors' detailed response to the review by Matheus costa
See the authors' detailed response to the review by Roberto M.C. Guedes
See the authors' detailed response to the review by Francesca Piras

Introduction

The question of routine surveillance to monitor Brachyspira species infections in pigs at local, national and international levels is addressed by experts and authorities (Hampson et al., 2015). The major pathogenic intestinal spirochetes affecting pigs during the growing-finishing stage of production include Brachyspira hyodysenteriae and Brachyspira pilosicoli. B. hyodysenteriae is the cause of swine dysentery (SD) – a severe, enteric disease of pigs characterized by mucohemorrhagic diarrhea and inflammation in the large intestine. B. hyodysenteriae is present worldwide and affects the economics of pig production, resulting in mortality, growth rate losses and substantial antibiotic costs. Another brachyspiral disease with mild colitis and diarrhea is porcine intestinal spirochetosis or porcine colonic spirochetosis (PIS/PCS). B. pilosicoli is the causative agent of PIS/PCS, a disease that implies an important economic cost resulting from reduced growth performance and poor feed conversion (Duhamel, 1998). Most Brachyspira species have a restricted host range, whereas B. pilosicoli colonizes a wide range of hosts, including humans, and has the potential for interspecies transmission. There is also a potential for zoonotic transmission, especially in places where animals and humans live in close proximity, or in people working with intensively farmed pigs or chickens, due to the increased risk of exposure. Some species of the genus Brachyspira, including B. pilosicoli, can cause the disease in humans. There are a few reports on B. pilosicoli-associated human intestinal spirochetosis (HIS) (Hampson, 2018). The subclinical colonization of pigs with B. pilosicoli is not uncommon and has been detected in several farms (Biksi et al., 2007). On other farms, B. pilosicoli were isolated from diseased pigs as the only causative agent or simultaneously with other enteric pathogens as part of a mixed infection (Reiner et al., 2011; Stege et al., 2000).

Recent changes in the management of pig farms and the movement of pigs within the EU have resulted in a shift in the relative prevalence of pathogenic Brachyspira species. There are very few studies addressing the prevalence of B. hyodysenteriae in pigs in Poland and only one concerning B. pilosicoli (Pławińska et al., 2004). The aim of the study was to assess the current occurrence of B. hyodysenteriae and B. pilosicoli in Polish pig herds. Moreover, associations between the presence of diarrhea or other intestinal pathogens and the occurrence of B. hyodysenteriae and B. pilosicoli in pigs were investigated.

Methods

Fecal samples

Fecal samples used in this study were submitted to the Department of Swine Diseases of the National Veterinary Research Institute (NVRI) for commercial laboratory diagnostics of selected porcine bacterial pathogens. Between January 2017 and August 2019, a total of 401 samples of pig feces were submitted to the NVRI. These samples originated from 95 different Polish pig herds, from pigs older than 7 weeks. All received fecal samples were submitted to the NVRI to be examined for the presence of B. hyodysenteriae and/or Lawsonia intracellularis. At that time, none of the diagnostic tools for B. pilosicoli identification were available for NVRI customers.

Owing to differing reasons for testing submitted fecal samples, three groups were distinguished. The first group of samples (n=218) were obtained from pigs subjected to routine monitoring of herds free of one or both of the aforementioned pathogens (B. hyodysenteriae, L. intracellularis). The second group was made up of samples (n=70) from pigs with clinical signs of diarrhea, where B. hyodysenteriae or L. intracellularis was suspected to be a cause of disease. The last group of samples (n=113) was submitted to the laboratory due to unrecognized pathogen status and a history of diarrhea in the herd.

DNA extraction and PCR

Total genomic DNA was extracted from the fecal samples using a commercial isolation kit (Genomic Mini, A&A Biotechnology, Gdynia, Poland), according to manufacturer’s recommendations. Extracted DNA samples were stored at -20°C until examination. All samples were tested by separate singleplex real-time PCR assays for B. hyodysenteriae and L. intracellularis immediately after samples submission according to the methods described previously (Zmudzki et al., 2012). Detection of B. pilosicoli by real-time PCR was performed in July and August 2019 (Ståhl et al., 2011). Primers were obtained from a commercial source (Genomed S.A., Poland). The sequences of primers and probes are as follows: for B. hyodysenteriae (forward primer: 5'-TATGAAGAAGGCAGCAGACGTTTAT-3', reverse primer: 5'-GTAGGAAGAAGAAATCTGACAATGCA-3', probe: 5'-FAM-ACACAATCATGCTGAAGC-TAMRA-3') (Akase et al., 2009); for B. pilosicoli (forward primer: 5'-GTAGTCGATGGGAAACAGGT-3', reverse primer: 5'-TTACTCACCACAAGTCTCGG-3', probe: 5'-FAM-TATTCGACGAGGATAACCATCACCT-BHQ-1-3') (Ståhl et al., 2011); for L. intracellularis (forward primer: 5'-GCGCGCGTAGGTGGTTATAT-3', reverse primer: 5'-GCCACCCTCTCCGATACTCA-3', probe: 5'-FAM-CACCGCTTAACGGTGGAACAGCCTT-TAMRA-3’) (Lindecrona et al., 2002). All assays were carried out using the Rotor-Gene Q real-time PCR system (Qiagen, Hilden, Germany).

Real-time PCR assays were run using a commercially available master mix Quantitect Probe PCR kit (Qiagen, Hilden, Germany). For B. hyodysenteriae, 12.5 μl of the master mix was combined with 0.5 μl of each primer, diluted to 20 μM and 0.5 μl of the probe, diluted to 20 μM and 6 μl of DNase-free water. The DNA template was added at 5 μl per reaction for a total reaction volume of 25 μl. PCR was run, as follows: 95°C for 15 mins, followed by 50 cycles at 95°C for 15 secs and 52°C for 1 min. For B. pilosicoli, 12.5 μl of the master mix was combined with 0.5 μl of each primer, diluted to 20 μM and 0.5 μl of the probe, diluted to 10 μM and 8 μl of DNase-free water. The DNA template was added at 3 μl per reaction for a total reaction volume of 25 μl. PCR was run as follows: 95°C for 15 min, followed by 40 cycles of 95°C for 15 sec and 60°C for 1 min. For L. intracellularis, 12.5 μl of the master mix was combined with 0.5 μl of each primer, diluted to 20 μM and 0.5 μl of the probe, diluted to 20 μM and 6 μl of DNase-free water. The DNA template was added at 5 μl per reaction for a total reaction volume of 25 μl. PCR was run as follows: 95°C for 15 min, followed by 40 cycles of 95°C for 15 sec and 62°C for 1 min.

Statistical analysis

A herd was defined as positive when at least one fecal sample taken from the herd had a positive PCR result. Percentages of positive samples/herds with a 95% two-sides exact binominal confidence interval (CI) were reported. Differences in the presence of pathogens between different fecal samples groups and association with L. intracellularis infection were established by a chi-square test (statistically significant at p < 0.05). Pairwise comparisons with Bonferroni corrections of the p-values were performed.

Results

Among a total of 401 samples 218 were submitted to the NVRI laboratory for the routine monitoring of pig herds. Of these, 70 samples originated from pigs with the clinical manifestation of diarrhea. The remaining 113 samples originated from herds with a history of diarrhea but of an unknown status, in terms of Brachyspira spp. occurrence. Underlying data are available on figshare (Dors et al., 2019).

B. pilosicoli was detected in 4.5% (95% CI, 2.5–7.0%) (18/401) of pig fecal samples. At the herd level 13.7% (95% CI, 7.5–22.3%) (13/95) of herds were positive for B. pilosicoli. B. hyodysenteriae was detected in 7.0% (95% CI, 4.7–9.9%) (28/401) of pig fecal samples and 18.9% (95% CI, 11.6–28.3%) (18/95) of pig herds were positive.

Out of 18 B. pilosicoli positive samples, the pathogen was detected alone in 5 samples; simultaneously with L. intracellularis in 9 samples; simultaneously with B. hyodysenteriae in 1 sample and in 3 samples was detected simultaneously with both of these bacteria.

Differences in the presence of B. hyodysenteriae and B. pilosicoli in the fecal samples of various origin (pigs with diarrhea, herds with a history of diarrhea, routine monitoring) are shown in Table 1.

Table 1. The differences in the presence of Brachyspira hyodysenteriae and Brachyspira pilosicoli in fecal samples obtained from healthy pigs and pigs with diarrhea.

Group of fecal samplesPositive samples, %
B. hyodysenteriaeB. pilosicoli
Pig with diarrhea22.8%*2.9%
Herds with history of diarrhea1.8%1.8%
Routine monitoring6.3%6.9%

*Statistically significant difference (p<0.05) between sample groups.

Additional analyses were completed to compare the influence of L. intracellularis infection and the presence of Brachyspira spp., in fecal samples. The occurrence of B. hyodysenteriae in pigs whose feces was confirmed to be positive for L. intracellularis was 7.3% (9/123), compared to 6.8% (19/278) in pigs negative for L. intracellularis with no statistical significance (p=0.861). However, considering the simultaneous occurrence of B. pilosicoli and L. intracellularis, we found that the percentage of samples positive for B. pilosicoli was significantly higher in pigs simultaneously infected by L. intracellularis 9.8% (12/123) compared to L. intracellularis-negative pigs 2.2% (6/278) (p<0.001).

Discussion and conclusions

The results of this study show that B. pilosicoli infections occur in Polish pig herds more frequently than it has been thought so far. A previous study reported only one positive sample among 127 samples from 23 pig farms (Pławińska et al., 2004). Our results show that B. pilosicoli is present in Polish pig herds, but that the prevalence is low, reaching 13.7% of herds and 4.5% of samples. Notably, considerably higher prevalence of B. pilosicoli infection has been detected in other countries, such as Germany (31.6%, Reiner et al., 2011), Denmark (19%, Stege et al., 2000) and Hungary (61.3%, Biksi et al., 2007). Therefore, the targeted sampling of pigs from age groups in which detection of this pathogen is most likely and random selection of Polish pig herds is necessary to assess the true prevalence of B. pilosicoli.

An association between B. pilosicoli infections in pigs and the occurrence of diarrhea in this study was not confirmed. Our results are in line with some previous reports (Biksi et al., 2007; Weber et al., 2015), but other authors have demonstrated positive associations between presence of diarrhea and B. pilosicoli detection (Fellström et al., 1996; Stege et al., 2001). It seems that the subclinical colonization of pigs by B. pilosicoli is predominant in pigs, in Poland. Considering the causality of PIS/PCS, other factors causing the development of diarrhea in pigs, besides the B. pilosicoli infection, should be considered. B. pilosicoli colonization and/or disease expression can be influenced by diet (Hopwood et al., 2002; Stege et al., 2001). Moreover, concurrent infection can influence B. pilosicoli colonization and disease manifestation.

In our study, we have found that samples positive for L. intracellularis are more likely to be positive with B. pilosicoli. Similar findings have been reported in previous studies (Biksi et al., 2007; Jacobson et al., 2003; Jacobson et al., 2005; Merialdi et al., 2003). Therefore, there is a need for further investigation to determine a risk factors and an association between the presence of B. pilosicoli in feces and the clinical signs or pig performance.

The occurrence of B. hyodysenteriae in our investigation was more common than B. pilosicoli and was higher than reported previously (Dors et al., 2015). Current results on the prevalence of B. hyodysenteriae could be biased, due to the large number of samples submitted to the NVRI with suspected clinical SD. Nonetheless, SD is still a common cause of diarrhea among pigs from Polish herds, despite improving biosecurity, management and disease control.

In conclusion, our study shows that B. pilosicoli infections occur in Polish pig herds, but the prevalence is at a low level and the presence of B. pilosicoli is not associated with the development of diarrhea in pigs. Secondly, B. hyodysenteriae is still a common cause of diarrhea among pigs from Polish herds. Moreover infection of L. intracellularis might be predisposing factor for B. pilosicoli occurrence in pigs.

Data availability

Figshare: A survey on the occurrence of Brachyspira pilosicoli and Brachyspira hyodysenteriae in growing-finishing pigs. https://doi.org/10.6084/m9.figshare.9878612.v1 (Dors et al., 2019).

This project contains data on detection of infection with each pathogen studied for each sample. 1, yes; 0, no.

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).

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Dors A, Czyżewska-Dors E and Woźniakowski G. A survey on the occurrence of Brachyspira pilosicoli and Brachyspira hyodysenteriae in growing-finishing pigs [version 3; peer review: 2 approved, 1 approved with reservations]. F1000Research 2021, 8:1702 (https://doi.org/10.12688/f1000research.20639.3)
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Version 2
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Reviewer Report 23 Mar 2021
Francesca Piras, Department of Veterinary Medicine, University of Sassari, Sassari, Italy 
Approved
VIEWS 8
The paper “A survey on the occurrence of Brachyspira pilosicoli and Brachyspira hyodysenteriae in growing-finishing pigs” evaluate occurrence of two pathogenic intestinal spirochetes in finishing pigs herd.
The presented manuscript is well written and sound.
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Piras F. Reviewer Report For: A survey on the occurrence of Brachyspira pilosicoli and Brachyspira hyodysenteriae in growing-finishing pigs [version 3; peer review: 2 approved, 1 approved with reservations]. F1000Research 2021, 8:1702 (https://doi.org/10.5256/f1000research.25154.r81218)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
  • Author Response 01 Apr 2021
    arkadiusz dors
    01 Apr 2021
    Author Response
    I would like to thank the Reviewer for all the comments to our article. I included all the amendments and suggestions in the new version of the manuscript.
    Competing Interests: No competing interests were disclosed.
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  • Author Response 01 Apr 2021
    arkadiusz dors
    01 Apr 2021
    Author Response
    I would like to thank the Reviewer for all the comments to our article. I included all the amendments and suggestions in the new version of the manuscript.
    Competing Interests: No competing interests were disclosed.
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Reviewer Report 23 Mar 2020
Roberto M.C. Guedes, Department of Veterinary Clinic and Surgery, Veterinary School, Federal University of Minas Gerais, Belo Horizonte, Brazil 
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I believe now the ... Continue reading
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Guedes RMC. Reviewer Report For: A survey on the occurrence of Brachyspira pilosicoli and Brachyspira hyodysenteriae in growing-finishing pigs [version 3; peer review: 2 approved, 1 approved with reservations]. F1000Research 2021, 8:1702 (https://doi.org/10.5256/f1000research.25154.r61312)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
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Reviewer Report 05 Dec 2019
Roberto M.C. Guedes, Department of Veterinary Clinic and Surgery, Veterinary School, Federal University of Minas Gerais, Belo Horizonte, Brazil 
Approved with Reservations
VIEWS 15
General comments:
This study describes the occurrence of pathogenic spirochetes for swine in Poland herds using routine diagnostic cases submitted to their reference laboratory. As a result, sampling was bias for a prevalence study, so the decision of just ... Continue reading
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Guedes RMC. Reviewer Report For: A survey on the occurrence of Brachyspira pilosicoli and Brachyspira hyodysenteriae in growing-finishing pigs [version 3; peer review: 2 approved, 1 approved with reservations]. F1000Research 2021, 8:1702 (https://doi.org/10.5256/f1000research.22699.r57051)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
  • Author Response 13 Mar 2020
    arkadiusz dors
    13 Mar 2020
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    I would like to begin by thanking the reviewer for the valuable comments. Below we have included our responses to specific comments.
     
    Figure 1 is illustrative but it is a repetition ... Continue reading
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  • Author Response 13 Mar 2020
    arkadiusz dors
    13 Mar 2020
    Author Response
    I would like to begin by thanking the reviewer for the valuable comments. Below we have included our responses to specific comments.
     
    Figure 1 is illustrative but it is a repetition ... Continue reading
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Reviewer Report 26 Nov 2019
Matheus costa, Faculty of Veterinary Medicine, Department of Farm Animal Health, Utrecht University, Utrecht, The Netherlands;  University of Minnesota, Minneapolis, USA 
Approved with Reservations
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I read with great interest this article, that sought to investigate the presence of Bhyo and Bpilo in polish herds. As the authors observed, this is a somewhat challenging goal: both bacterium can survive in the healthy host, thus it's ... Continue reading
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costa M. Reviewer Report For: A survey on the occurrence of Brachyspira pilosicoli and Brachyspira hyodysenteriae in growing-finishing pigs [version 3; peer review: 2 approved, 1 approved with reservations]. F1000Research 2021, 8:1702 (https://doi.org/10.5256/f1000research.22699.r55873)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
  • Author Response 13 Mar 2020
    arkadiusz dors
    13 Mar 2020
    Author Response
    I would like to begin by thanking the reviewer for the valuable comments. Below we have included our responses to specific comments.

    Methods - Fecal samples - Please include a numeric ... Continue reading
COMMENTS ON THIS REPORT
  • Author Response 13 Mar 2020
    arkadiusz dors
    13 Mar 2020
    Author Response
    I would like to begin by thanking the reviewer for the valuable comments. Below we have included our responses to specific comments.

    Methods - Fecal samples - Please include a numeric ... Continue reading

Comments on this article Comments (0)

Version 3
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Alongside their report, reviewers assign a status to the article:
Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions
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