Evaluation of early single dose vaccination on swine influenza A virus transmission in piglets: From experimental data to mechanistic modelling

Swine influenza A virus (swIAV) is a major pathogen affecting pigs with a huge economic impact and potentially zoonotic. Epidemiological studies in endemically infected farms permitted to identify critical factors favoring on-farm persistence, among which maternally-derived antibodies (MDAs). Vaccination is commonly practiced in breeding herds and might be used for immunization of growing pigs at weaning. Althoughinterference between MDAs and vaccination was reported in young piglets, its impact on swIAV transmission was not yet quantified. To this aim, this study reports on a transmission experiment in piglets with or without MDAs, vaccinated with a single dose injection at four weeks of age, and challenged 17 days post-vaccination. To transpose small-scale experiments to real-life situation, estimated parameters were used in a simulation tool to assess their influence at the herd level. Based on a thorough follow-up of the infection chain during the experiment, the transmission of the swIAV challenge strain was highly dependent on the MDA status of the pigs when vaccinated. MDA-positive vaccinated animals showed a direct transmission rate 3.6-fold higher than the one obtained in vaccinated animals without MDAs, estimated to 1.2. Vaccination nevertheless reduced significantly the contribution of airborne transmission when compared with previous estimates obtained in unvaccinated animals. The integration of parameter estimates in a large-scale simulation model, representing a typical farrow-to-finish pig herd, evidenced an extended persistence of viral spread when vaccination of sows and single dose vaccination of piglets was hypothesized. When extinction was quasi-systematic at year 5 post-introduction in the absence of sow vaccination but with single dose early vaccination of piglets, the extinction probability fell down to 33% when batch-to-batch vaccination was implemented both in breeding herd and weaned piglets. These results shed light on a potential adverse effect of single dose vaccination in MDA-positive piglets, which might lead to longer persistence of the SwIAV at the herd level.

Influence of different CCD angles on osseointegration and radiological changes after total hip arthroplasty of a triple wedge shape cementless femoral stem: a prospective cohort study

PURPOSE

The purpose of this study was to evaluate the osseointegration and radiological outcomes in patients after total hip arthroplasty, hypothesizing different load patterns with one cementless stem design and different CCD angles (CLS Spotorno femoral stem 125° vs 135°).

METHODS

All cases of degenerative hip osteoarthritis fulfilling strict inclusion criteria were treated with cementless hip arthroplasty between 2008 and 2017. Ninety-two out of one hundred six cases were clinically and radiologically examined three and 12 months after implantation. Two groups with each 46 patients were rendered prospectively and compared in clinical (Harris Hip Score) and radiological outcome.

RESULTS

At final follow-up, no significant difference regarding Harris Hip Score was detected between the two groups (mean 99.2 ± 3.7 vs. 99.3 ± 2.5; p = 0.73). Cortical hypertrophy was found in none of the patients. Stress shielding was seen in a total of 52 hips (n = 27 vs. n = 25; 57% of the 92 hips). No significant difference regarding stress shielding was detected when comparing both groups (p = 0.67). Significant bone density loss was detected in Gruen zone one and two in the 125° group. The 135° group showed significant radiolucency in Gruen zone seven. No overall radiological loosening or subsidence of the femoral component was observed.

CONCLUSION

According to our results, the use of a femoral component with a 125° CCD angle versus a 135° CCD did not result in a different osseointegration and load transfer with a clinically relevant significance.

Atrial flutter caused by migration of a superior vena cava stent into the right atrium

We describe the case of a patient presenting with an atrial flutter mechanically induced by a stent migration from the superior vena cava to the right atrium.

Laparoscopic Extraperitoneal Approach to Bilateral Pelvic Lymph Node Dissection in Low Rectal Cancer: Technique with Video and 3D Modeling

BACKGROUND

Lateral pelvic lymph node dissection for rectal cancer is a difficult technique due to the complex pelvic anatomy. Recent series have underlined the importance of lateral lymphadenectomy in selective patients to prevent local recurrence of rectal cancer.

METHODS

A 65-year-old woman was diagnosed with locally advanced rectal adenocarcinoma of the low rectum with right and left lateral pelvic lymph nodes of respectively 9 and 13 mm. After chemotherapy followed by radiotherapy, the size of the right internal iliac lymph nodes remained enlarged to 5 mm. A laparoscopic extraperitoneal approach was used for total mesorectal excision, complete mesocolic excision, and bilateral lateral lymph node dissection. The extraperitoneal space was divided into the subperitoneal space dissected by a transanal approach and the retroperitoneal space dissected by a transabdominal approach.

RESULTS

The operating time was 303 min, and the estimated blood loss was 270 ml. No intraoperative adverse events occurred. Bilateral lymph node dissection was performed with obturator nerve and neurovascular bundle sparing. A postoperative complication classified as Clavien 3a arose with a pelvic infection but no anastomotic leakage. Final pathology disclosed T3N1M0 adenocarcinoma with free surgical margins. The patient never had urinary dysfunction.

CONCLUSIONS

The laparoscopic extraperitoneal approach to lateral pelvic lymph node dissection is feasible. For lateral lymph node dissection, the transanal approach may have some advantages over the standard transabdominal approach, with better visibility of and access to the distal internal iliac area. This video may help oncological surgeons to perform this new and complex procedure.

Enhanced structural and magnetic properties of fcc colloidal crystals of cobalt nanoparticles

We report the elaboration of supercrystals made up of dodecanoic acid-coated 8.1 nm-Co nanocrystals with controlled supercrystallinity, morphology and magnetic properties. Supercrystal growth is controlled using a solvent-mediated ligand-ligand interaction strategy. Either face-centered cubic supercrystalline films or single colloidal crystals composed of cobalt nanocrystals are obtained. The change in supercrystal morphology is explained by Flory-type solvation theory using Hansen solubility colloidal parameters. The use of the same batch of Co nanocrystals for the fabrication of supercrystalline films and colloidal crystals enables accurate comparative structural and magnetic studies using (high-resolution) transmission electron microscopy, field emission gun scanning electron microscopy, grazing incidence small-angle X-ray scattering and vibrating sample magnetometry. The nearest neighbor distance between nanoparticles is interpreted using theoretical models proposed in the literature. We evidence the increase in both geometric anisotropy and magnetic dipolar interactions for colloidal crystals compared to supercrystalline films.

A new agarose-based microsystem to investigate cell response to prolonged confinement

Emerging evidence suggests the importance of mechanical stimuli in normal and pathological situations for the control of many critical cellular functions. While the effect of matrix stiffness has been and is still extensively studied, few studies have focused on the role of mechanical stresses. The main limitation of such analyses is the lack of standard in vitro assays enabling extended mechanical stimulation compatible with dynamic biological and biophysical cell characterization. We have developed an agarose-based microsystem, the soft cell confiner, which enables the precise control of confinement for single or mixed cell populations. The rigidity of the confiner matches physiological conditions and its porosity enables passive medium renewal. It is compatible with time-lapse microscopy, in situ immunostaining, and standard molecular analyses, and can be used with both adherent and non-adherent cell lines. Cell proliferation of various cell lines (hematopoietic cells, MCF10A epithelial breast cells and HS27A stromal cells) was followed for several days up to confluence using video-microscopy and further documented by Western blot and immunostaining. Interestingly, even though the nuclear projected area was much larger upon confinement, with many highly deformed nuclei (non-circular shape), cell viability, assessed by live and dead cell staining, was unaffected for up to 8 days in the confiner. However, there was a decrease in cell proliferation upon confinement for all cell lines tested. The soft cell confiner is thus a valuable tool to decipher the effects of long-term confinement and deformation on the biology of cell populations. This tool will be instrumental in deciphering the impact of nuclear and cytoskeletal mechanosensitivity in normal and pathological conditions involving highly confined situations, such as those reported upon aging with fibrosis or during cancer.

Exposure of pregnant women to organophosphate insecticides and child motor inhibition at the age of 10-12 years evaluated by fMRI

BACKGROUND

Organophosphate pesticides (OP) are widely used for both agricultural and domestic purposes. Epidemiological studies suggest neurotoxicity in children after exposure to organophosphates pesticides (OP) at low levels but possible mechanism is still unclear.

OBJECTIVES

We aimed at investigating the effects of prenatal exposure to OPs on inhibitory control of 10-12 year-old-children assessed by a motor inhibition task during functional magnetic resonance imaging (fMRI).

METHODS

Ninety-five children from the PELAGIE cohort (Brittany-France, from 2002) underwent a fMRI examination during which inhibition was assessed by a Go/No-Go task. Task performance was assessed by average response latency, commission rate and composite performance score (PS). Whole brain activation was estimated by modeling the hemodynamic response related to inhibition demand and successful inhibition. OP exposure was assessed by measuring six dialkylphosphate (DAP) metabolites in the urine of women in early pregnancy (<19 WG). Concentrations were summed to obtain overall levels of diethylphosphate (DE), dimethylphosphate (DM) and total non-specific metabolites (DAP), standardized to homogenize sampling conditions and categorized into levels of exposure: low (reference), moderate or high. Regression models were adjusted for potential cofounders considered by restriction and statistical criteria.

RESULTS

Moderate levels of DAP were associated with a decreased commission rate (β = -6.65%, p = 0.04), indicating improved performance. Increasing levels of DM and DE were associated with decreased brain activity in the left inferior and bilateral superior frontal regions during successful inhibition. We did not observe any differential activation related to inhibitory demands.

DISCUSSION

These results suggest that prenatal OPs may be associated with altered pattern of brain activity in regions related to inhibition among children and need to be confirmed by additional studies.

FRI0450 MEASURES OF DISEASE SEVERITY PREDICT DISABILITY AND QUALITY OF LIFE DIFFERENTLY IN RHEUMATOID ARTHRITIS AND CHRONIC CHIKUNGUNYA DISEASE

Background:

Chronic rheumatological manifestations similar to those of rheumatoid arthritis (RA) have been described after chikungunya virus infection. However, the clinical significance of the symptoms and disease severity in the two conditions has not been directly compared.

Objectives:

To compare, using identical measures of disease severity and patient outcomes, the impact of disease severity measures and symptoms on outcomes in RA and chronic chikungunya disease.

Methods:

Forty patients with chronic chikungunya arthralgia two years post-infection and 40 matched patients with RA were enrolled in Roraima, Brazil. Twenty-eight joints were assessed for tenderness and swelling, a pain intensity visual analogue scale, musculoskeletal stiffness questionnaire, modified Health Assessment Questionnaire and the EuroQol EQ5D-5L quality of life assessment were completed. The importance of the various measures of disease severity were analysed using Spearman’s rank correlation and regression analysis.

Results:

Tender and swollen joint counts, pain and stiffness were all predictive of the HAQ disability index in RA, but only stiffness was significantly associated with disability in chikungunya patients (Table 1). Tender and swollen joint counts, pain and stiffness were predictive for all EQ5D quality of life domains (except anxiety/depression) in RA patients. In contrast, in chikungunya disease, tender joint counts were predictive only of usual daily activities; pain was predictive of impaired mobility, self-care and discomfort, while stiffness was predictive for the mobility and anxiety/depression domains (Figure 1). Swollen joint counts were not associated with any of the patient outcomes in chikungunya disease. Linear regression analysis confirmed (p=0.003) that the effect of swollen joint count on the HAQ disability index depends on the underlying disease.

Table 1.

Association of disease severity with HAQ disability index in rheumatoid and CHIKV+ arthritis

Severity measureRheumatoid arthritisCHIKV+ arthritisr (p)r (p)Tender joint count0.56 (0.0002)0.24 (0.14)Swollen joint count0.60 (<0.0001)0.002 (0.99)Joint pain (VAS)0.55 (0.0002)0.29 (0.07)Stiffness severity0.57 (0.0001)0.38 (0.02)Figure 1.

Association of disease severity with quality of life domains in rheumatoid and CHIKV+ arthritis

Conclusion:

The value of all the disease severity measures tested in RA were confirmed, but tender joint counts may have more limited value in the assessment of chronic chikungunya disease. Joint swelling appears to have little impact for chikungunya patients, while stiffness appears to be an important metric to quantify chikungunya arthritis disease severity.

Disclosure of Interests:

Hugh Watson Shareholder of: Sanofi, Employee of: Sanofi, Ramão Luciano Nogueira-Hayd: None declared, Maony Rodrigues-Moreno: None declared, Felipe Naveca: None declared, Giulia Calusi: None declared, Richard Amdur: None declared, Karol Suchowiecki: None declared, Gary S. Firestein: None declared, Gary Simon: None declared, Aileen Chang: None declared

CinéBreast-factors influencing the time to first metastatic recurrence in breast cancer: Analysis of real-life data from the French ESME MBC database

Purpose

The Time to First Metastatic Recurrence (TFMR) could be considered as an indirect reflection of the tumour growth kinetics which plays an important role in cancer. Molecular subtypes such as expression of estrogen receptor are known predictive factors of TFMR. The CinéBreast study aimed to identify predictive factors of the time to TFMR.

Methods

The French Epidemiological Strategy and Medical Economics (ESME) Metastatic Breast Cancer (MBC) Database (NCT03275311) was used, which contains data from a cohort of metastatic breast cancer patients from 2008 to 2016 using retrospective data collection. It is a national multi-centre database. The impact of TFMR on overall survival (OS) since first metastasis was also evaluated.

Results

Among 16 702 patients recorded in the ESME MBC database, 10 595 had an initially localised breast cancer with hormone receptor (HR) and HER2 status available, with a metastatic recurrence. Median follow up was 56 months. Median TFMR was 59 months (<24: 20%, 24–60: 31%, 60–120: 25%, >120: 24%). HER2+ and TNBC were respectively 4 times and 12 times (p < 0.0001) more likely to have a recurrence within 2 years when compared to the luminal subgroup. Short TFMR and HR-/HER2-subtype significantly correlated with a poor OS in multivariate analysis.

Some patients with MBC (20% in HER2+, 10% in ER+/HER2-and <5% in the ER-/HER2-) were long-term survivors in all 3 subgroups.

Conclusions

In this large-scale real-life data study, patients with a TNBC metastatic recurrence had a shorter TFMR. Short TFMR significantly correlated with worse overall survival.

•

ESME is a large-scale real-life database of 16 702 metastatic breast cancer patients.

•

A short time to first metastatic recurrence is associated with poor overall survival.

•

Triple-negative tumours were more likely to recur early than HR+ and HER2+ tumours.

Continuously Sheared Granular Matter Reproduces in Detail Seismicity Laws

We introduce a shear experiment that quantitatively reproduces the main laws of seismicity. By continuously and slowly shearing a compressed monolayer of disks in a ringlike geometry, our system delivers events of frictional failures with energies following a Gutenberg-Richter law. Moreover, foreshocks and aftershocks are described by Omori laws and interevent times also follow exactly the same distribution as real earthquakes, showing the existence of memory of past events. Other features of real earthquakes qualitatively reproduced in our system are both the existence of a quiescence preceding some main shocks, as well as magnitude correlations linked to large quakes. The key ingredient of the dynamics is the nature of the force network, governing the distribution of frictional thresholds.

Abstract P5-17-04: Metastatic inflammatory breast cancer: Clinical features and outcomes in the national, multicentric, real-life ESME cohort

Background:Primary inflammatory breast cancer (IBC) is a rare and aggressive form of breast cancer. Survival of IBC patients has been improved by multimodal therapy. However 5-year overall survival (OS) still remains close to 50-60%, due to high risk of disseminated disease. Given the low incidence, prognosis of metastatic cases stages is poorly described.

Methods:This study aimed to describe OS of IBC (T4d AJCC TNM classification) with upfront or recurrent metastatic disease compared with non-IBC patients in the ESME database (N=16,702 patients). OS was calculated from the diagnosis of metastasis to the date of death (from any cause), or censored to date of latest news. Secondary objectives included progression-free survival (PFS).

Results:From 2008 to 2014, 7,465 patients with diagnosis of MBC and known clinical status of their primary tumor (T) were identified, including 582 IBC (T4d) and 6,883 non-IBC. As expected, metastatic IBC was associated with pejorative features compared to non-IBC, with less hormonal receptors-positive tumors (44% vs 65.6%), more HER2-positive (30% vs 18.6%) or triple-negative (25.9% vs 15.8%) cases (p&lt;0.001), more frequent upfront M1 stage (53.3% vs 27.7%; p&lt;0.001), and shorter median disease-free interval (2.02 years vs. 4.9 years; p&lt;0.001). With a median follow-up of 50.2 months (0-104), median OS was 28.4 [95%CI 24-33.8] versus 37.2 months [95%CI 36.1-38.5] in metastatic IBC and non-IBC cases respectively (p&lt;0.0001, log-rank test). By multivariate Cox model with adjustment for major prognostic factors [including age, disease-free interval, type of relapse, visceral metastases, molecular subtype, grade], OS was significantly shorter in the metastatic IBC group compared with non-IBC group (HR 1.25 [95%CI 1.1-1.4], p=0.0002). Of note, survival of metastatic IBC patients improved over the last years: median OS 24 months [95%CI 20-31.9], 29 months [95%CI 21.7-39.9] and 36 months [95%CI 27.9-NE] if diagnosed before 2011, between 2011 and 2012, or after 2012 respectively (p=0.003). Such improvement was not observed in non-IBC patients. IBC was associated with shorter median PFS under first line systemic treatment compared with non-IBC (7.2 months [95%CI 6.6-8.3] vs 9.5 months [95%CI 9.1-9.8] respectively, p=0.0136). This was maintained in a multivariate Cox model adjusting for same factors as for OS (HR 1.15 [95%CI 1-1.3], p=0.0050).

Compared with non-IBC, synchronous metastatic IBC showed worse median OS and PFS (39.9 months [95%CI 34.2-45.3] vs 48.4 months [95%CI 46.3-50.8], p=0.0035; 10 months [95%CI 8.8-12.7] vs 14.5 months [95%CI 13.6-15.7], p=0.0027, respectively. Similar results were obtained in metachronous metastatic cases (20.01 months [95%CI 17.1-21.2] vs 32.8 months [95%CI 31.5-34.3], p&lt;0.0001; 5.1 months [95%CI 4.1-6] vs 7.9 months [95%CI 7.6-8.3], p&lt;0.0001, respectively).

Conclusion:In this large national and multicentric study, IBC is a major and independent factor associated with adverse outcome in metastatic setting. Of note, the independent adverse impact on PFS identified in this study may suggest a lower sensitivity of metastatic IBC to available therapeutics. However, results seem to improve in the last years. Detailed analysis according to phenotype will be available.

Citation Format: Monneur A, Bertucci F, Lardy-Cleaud A, Augereau P, Debled M, Levy C, Mouret-Reynier MA, Coudert B, Mailliez A, Bachelot T, Ferrero J-M, Guiu S, Uwer L, Campone M, Cottu P, Jouannaud C, De la Motte Rouge T, Leheurteur M, Petit T, Pistilli B, Dalenc F, Simon G, Robain M, Viens P, Lerebours F, Gonçalves A. Metastatic inflammatory breast cancer: Clinical features and outcomes in the national, multicentric, real-life ESME cohort [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-17-04.

Vergleich zwischen szintigraphischen und neurochirurgischen Befunden bei Hirntumoren

Bei einem selektiven Krankengut von 120 operierten Hirntumoren wurde der neurochirurgische Befund den Ergebnissen der Hirn-Szintigraphie gegenübergestellt. Die Auswahl der Fälle wurde auf die häufigen Tumor-Arten beschränkt, wie Meningeome, Astrozytome, Glioblastome, Oligodendrogliome, Neurinome und Metastasen. Aus dem Operationsbefund wurden die Lokalisation, die Tumorgröße, das Ausmaß der Vaskularisation sowie das Vorhandensein von Zysten und Nekrosen ausgewertet. Diese Daten wurden in Beziehung gesetzt zum Verhalten in der Radioangiographie und dem Grad der Aktivitätsanreicherung in den szintigraphischen Spätbildern.

Von den Hirntumoren waren 105 Fälle szintigraphisch nachweisbar.

In der Artdiagnostik war die Radioangiographie den szintigraphischen Spätbildern deutlich überlegen. Die Tumorgröße wurde szintigraphisch bei den Meningeomen etwas zu groß ermittelt, bei den übrigen Tumoren war die szintigraphische Tumorgröße kleiner als die im Operationsbefund angegebene.

Der Grad der Anreicherung in den Spätbildern zeigte eine Korrelation zur Vaskularisation. Dagegen bestand keine Korrelation zwischen der Vaskularisation und dem radioangiographischen Verhalten bei den Glioblastomen. Dieser Befund bedarf der weiteren Überprüfung. In der Hälfte der Fälle mit Zysten und Nekrosen waren Inhomogeneitäten in der Aktivitätsanreicherung des Tumors auf den Spätbildern erkennbar.

The risk of depression, suicidal ideation and suicide attempt in patients with psoriasis, psoriatic arthritis or ankylosing spondylitis

BACKGROUND

Sparse information is available concerning mental health issues in psoriasis, psoriatic arthritis (PsA) and ankylosing spondylitis (AS) patients.

OBJECTIVE

To estimate risk of depression, suicidal ideation and suicide attempt in patients with psoriasis, PsA and AS, respectively, compared with the general population.

METHODS

This population-based cohort study analysed 36 214 psoriasis patients, 5138 PsA patients and 1878 AS patients who were frequency-matched with a general population cohort. Annual incidence rate of depression, suicidal ideation and suicide attempt was calculated separately for psoriasis, PsA and AS.

RESULTS

There was an increased risk of depression in the three cohorts; adjusted IRR: psoriasis, 1.14 (95% CI, 1.11, 1.17); PsA, 1.22 (95% CI, 1.16, 1.29); AS, 1.34 (95% CI, 1.23, 1.47). There was no significantly increased risk for suicidal ideations or suicide attempt among psoriasis, PsA or AS patients.

LIMITATIONS

Patients were not excluded if previously diagnosed with depression, suicidal ideation or suicide attempt. Suicide attempt and completed suicide analyses were not adjusted for presence of depression. Use of systemic psoriasis treatment to measure severe psoriasis could lead to psoriasis severity misclassification.

CONCLUSION

The risk of depression, but not suicidal ideation or suicide attempt, was significantly increased in patients with psoriasis, PsA and AS.

The respiratory DC/macrophage network at steady-state and upon influenza infection in the swine biomedical model

Human and mouse respiratory tracts show anatomical and physiological differences, which will benefit from alternative experimental models for studying many respiratory diseases. Pig has been recognized as a valuable biomedical model, in particular for lung transplantation or pathologies such as cystic fibrosis and influenza infection. However, there is a lack of knowledge about the porcine respiratory immune system. Here we segregated and studied six populations of pig lung dendritic cells (DCs)/macrophages (Mθs) as follows: conventional DCs (cDC) 1 and cDC2, inflammatory monocyte-derived DCs (moDCs), monocyte-derived Mθs, and interstitial and alveolar Mθs. The three DC subsets present migratory and naive T-cell stimulation capacities. As observed in human and mice, porcine cDC1 and cDC2 were able to induce T-helper (Th)1 and Th2 responses, respectively. Interestingly, porcine moDCs increased in the lung upon influenza infection, as observed in the mouse model. Pig cDC2 shared some characteristics observed in human but not in mice, such as the expression of FCɛRIα and Langerin, and an intra-epithelial localization. This work, by unraveling the extended similarities of the porcine and human lung DC/Mθ networks, highlights the relevance of pig, both as an exploratory model of DC/Mθ functions and as a model for human inflammatory lung pathologies.

Factors associated with herd-level PRRSV infection and age-time to seroconversion in farrow-to-finish herds

Factors associated with porcine reproductive and respiratory syndrome virus (PRRSV) infection were investigated in 109 herds. Serums from four batches of pigs (4, 10, 16 and 22 weeks, 15 pigs/batch) were tested by ELISA for PRRSV antibodies. Infection by Mycoplasma hyopneumoniae (Mhp), Actinobacillus pleuropneumoniae, H1N1 and H1N2 swine influenza A viruses (swIAV) and PCV2 were detected by specific serological or PCR tests. Data related to herd characteristics, biosecurity, management housing and climatic conditions were collected during a herd visit. Factors associated with the herd's PRRSV seropositive status were identified by logistic regression. Large herd size, the lack of disinsectisation in the gestation facilities, on-farm semen collection, a short time-period for gilt quarantine and a low temperature setpoint for the ventilation controller in the fattening room significantly increased the odds of a herd being seropositive for PRRSV. Infection by Mhp and H1N2 swIAV were associated with a PRRSV seropositive status. A Cox proportional hazards model was used to identify the factors associated with the age-time to seroconversion in infected herds. Joint housing for the gilts and sows when lactating, a large nursery pen, a small number of pens per fattening room and lack of all-in all-out management in the fattening section significantly reduced the age-time to seroconversion. A small range of temperatures controlling ventilation rate in the nursery room was also associated with time to PRRSV seroconversion. Infection by Mhp and a high PCV2 infection pressure were associated with a shorter time to seroconversion. Biosecurity measures minimising the risk of introducing PRRSV into the herd, management practices reducing contacts between animals from different batches and within batches and favourable climatic conditions should be implemented to better control PRRSV infection.