Effect of Spatial Separation of Pigs on Spread of Streptococcus suis Serotype 9

Dekker, Niels; Bouma, A.; Daemen, Ineke; Klinkenberg, Don; Leengoed, Leo van; Wagenaar, Jaap A.; Stegeman, Arjan

doi:10.1371/journal.pone.0061339

Cited by 36 publications

(47 citation statements)

References 47 publications

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“…The presence of S. suis in the air of SCB confirms their findings and the data of Berthelot-Herault (35) and showed that spatial separation of animal groups within a compartment would not prevent S. suis transmission on a farm (59). In Canada, the United States, and Europe at this time, S. suis infections in humans have most often been restricted to workers in close contact with pigs or contaminated swine products.…”

Section: Discussionsupporting

confidence: 77%

“…Dekker et al determined that prevention of direct contact with infected animals decreases the risk of infection in susceptible pigs (59). The presence of S. suis in the air of SCB confirms their findings and the data of Berthelot-Herault (35) and showed that spatial separation of animal groups within a compartment would not prevent S. suis transmission on a farm (59).…”

Section: Discussionmentioning

confidence: 84%

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Detection of Streptococcus suis in Bioaerosols of Swine Confinement Buildings

Bonifait

Veillette

Létourneau

et al. 2014

Appl Environ Microbiol

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Streptococcus suis is an important swine pathogen that can cause septicemia, meningitis, and pneumonia. Also recognized as an emerging zoonotic agent, it is responsible for outbreaks of human infections in Asian countries. Serotype 2 is the predominant isolate from diseased animals and humans. The aerosolization of S. suis in the air of swine confinement buildings (SCB) was studied. The presence of S. suis in bioaerosols was monitored in SCB where cases of infection had been reported and in healthy SCB without reported infections. Using a quantitative-PCR (qPCR) method, we determined the total number of bacteria (1 × 10(8) to 2 × 10(8) airborne/m(3)), total number of S. suis bacteria (4 × 10(5) to 10 × 10(5) airborne/m(3)), and number of S. suis serotype 2 and 1/2 bacteria (1 × 10(3) to 30 × 10(3) airborne/m(3)) present in the air. S. suis serotypes 2 and 1/2 were detected in the air of all growing/finishing SCB that had documented cases of S. suis infection and in 50% of healthy SCB. The total number of bacteria and total numbers of S. suis and S. suis serotype 2 and 1/2 bacteria were monitored in one positive SCB during a 5-week period, and it was shown that the aerosolized S. suis serotypes 2 and 1/2 remain airborne for a prolonged period. When the effect of aerosolization on S. suis was observed, the percentage of intact S. suis bacteria (showing cell membrane integrity) in the air might have been up to 13%. Finally S. suis was found in nasal swabs from 14 out of 21 healthy finishing-SCB workers, suggesting significant exposure to the pathogen. This report provides a better understanding of the aerosolization, prevalence, and persistence of S. suis in SCB.

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Section: Discussionsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 84%

Detection of Streptococcus suis in Bioaerosols of Swine Confinement Buildings

Bonifait

Veillette

Létourneau

et al. 2014

Appl Environ Microbiol

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“…The proportion of infected pigs at 6 weeks later is presented while raising the litters separated or randomly mixed after weaning (with 95% percentiles). (Dekker et al, 2013) and several viral pathogens (e.g. Classical Swine Fever virus (Klinkenberg et al, 2002), Footand-Mouth disease virus (Eblé et al, 2006) and Porcine circovirus (PCV2) (Andraud et al, 2008)).…”

Section: Discussionmentioning

confidence: 99%

Transmission of Actinobacillus pleuropneumoniae among weaned piglets on endemically infected farms

Tobias

Bouma

Broek

et al. 2014

Preventive Veterinary Medicine

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Clinical outbreaks due to Actinobacillus pleuropneumoniae occur recurrently, despite the wide-scale use of antimicrobials or vaccination. Therefore, new approaches for the prevention and control of these outbreaks are necessary. For the development of alternative measures, more insight into the transmission of the bacterium on farms is necessary. The aim of this cohort study was to quantify transmission of A. pleuropneumoniae amongst weaned piglets on farms. We investigated three possible transmission routes: (i) indirect transmission by infected piglets within the same compartment, (ii) transmission by infected pigs in adjacent pens and (iii) transmission by direct contact within pens. Additionally, we evaluated the effect of independent litter characteristics on the probability of infection. Two farms participated in our study. Serum and tonsil brush samples were collected from sows pre-farrowing. Serum was analysed for antibodies against Apx toxins and Omp. Subsequently, tonsil brush samples were collected from all piglets from these dams (N=542) in three cohorts, 3 days before weaning and 6 weeks later. Tonsil samples were analysed by qPCR for the presence of the apxIVA gene of A. pleuropneumoniae. Before weaning, 25% of the piglets tested positive; 6 weeks later 47% tested positive. Regression and stochastic transmission models were used to assess the contribution of each of the three transmission routes and to estimate transmission rates. Transmission between piglets in adjacent pens did not differ significantly from that between non-adjacent pens. The transmission rate across pens was estimated to be 0.0058 day(-1) (95% CI: 0.0030-0.010), whereas the transmission rate within pens was ten times higher 0.059 day(-1) (95% CI: 0.048-0.072). Subsequently, the effects of parity and serological response of the dam and litter age at weaning on the probability of infection of pigs were evaluated by including these into the regression model. A higher dam ApxII antibody level was associated with a lower probability of infection of the pig after weaning; age at weaning was associated with a higher probability of infection of the pig after weaning. Finally, transmission rate estimates were used in a scenario study in which the litters within a compartment were mixed across pens at weaning instead of raising litter mates together in a pen. The results showed that the proportion of infected piglets increased to 69% if litters were mixed at weaning, indicating that farm management measures may affect spread of A. pleuropneumoniae.

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“…Modeling the travel as a random walk, i.e., diffusion in 2D space (and including the decay of the pathogen while traveling), has the advantage that it explains both the delay and the difference in delay between the two bacterium species. Modeling it only as a buildup in the environment without a spatial component (16) would not explain the difference in delay. Although in our current model the diffusion is precisely following a 2D diffusion equation, this might not necessarily be the case; the movement of the infectious material in space does not have to be a random walk as we assumed.…”

Section: −1mentioning

confidence: 99%

Small distances can keep bacteria at bay for days

Bunnik

Ssematimba

Hagenaars

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Transmission of pathogens between spatially separated hosts, i.e., indirect transmission, is a commonly encountered phenomenon important for epidemic pathogen spread. The routes of indirect transmission often remain untraced, making it difficult to develop control strategies. Here we used a tailor-made design to study indirect transmission experimentally, using two different zoonotic bacteria in broilers. Previous experiments using a single bacterial species yielded a delay in the onset of transmission, which we hypothesized to result from the interplay between diffusive motion of infectious material and decay of infectivity in the environment. Indeed, a mathematical model of diffusive pathogen transfer predicts a delay in transmission that depends both on the distance between hosts and on the magnitude of the pathogen decay rate. Our experiments, carried out with two bacterial species with very different decay rates in the environment, confirm the difference in transmission delay predicted by the model. These results imply that for control of an infectious agent, the time between the distant exposure and the infection event is important. To illustrate how this can work we analyzed data observed on the spread of vancomycin-resistant Enterococcus in an intensive care unit. Indeed, a delayed vancomycin-resistant Enterococcus transmission component was identified in these data, and this component disappeared in a study period in which the environment was thoroughly cleaned. Therefore, we suggest that the impact of control strategies against indirect transmission can be assessed using our model by estimating the control measures' effects on the diffusion coefficient and the pathogen decay rate.

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Effect of Spatial Separation of Pigs on Spread of Streptococcus suis Serotype 9

Cited by 36 publications

References 47 publications

Detection of Streptococcus suis in Bioaerosols of Swine Confinement Buildings

Detection of Streptococcus suis in Bioaerosols of Swine Confinement Buildings

Transmission of Actinobacillus pleuropneumoniae among weaned piglets on endemically infected farms

Small distances can keep bacteria at bay for days

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